Tips For Touching-Up A Powder Coated Finish

Pump Casting With Powder Coated FinishOne of the many advantages powder coating has over wet paint is the variety of ways you can fine-tune and rework a powder coated finish. This article discusses some of the different touch-up techniques you can use to clean up your work and get the best overall quality for your powder coating projects.

Why Should You Touch-Up Your Powder Coated Finish

Visual Appeal. This is the obvious reason for fixing a powder coated finish. To most customers, if it doesn’t look right, it isn’t acceptable.

Performance. Some powder coatings are purely functional, so they don’t need to be aesthetically perfect. Usually there are one or more standards (such as corrosion resistance) that have to be met. A defect can compromise the finish integrity and cause a part to fail to meet a specific customer’s standards.

Warranty. If the powder coated part has any sort of warranty, then special care should be made to make sure the part passes end-of-the line QC testing. A part may look great and have no apparent defects, but if it does not pass the customer’s minimum testing standards, a repair or rework is needed.

When Is The Right Time To Do Touch-Up Work?

The best time to catch your coating mistakes is prior to curing the powder. The powder can easily be blown off with compressed air or wiped off and then reapplied with very little hassle. Get in the habit of checking your parts for application errors before you start the curing process. Every mistake you catch here will save you time, effort and money later.

Common Powder Coating Touch-up Techniques After Curing

It’s not always possible to catch coating errors, especially if there are overbaking or underbaking issues with your oven. When dealing with a defective finish, you should ask yourself: will a touched-up surface be acceptable -both visually and from a performance standpoint-or should you repaint? In either case, if you have to resolve a finish problem, here are some of the most effective techniques to use once a powder coated part has been cured using Reliant’s products:

Liquid Paint Touch-Up

Many manufacturers use color-matched liquid enamels to cover hook marks, missed areas, Faraday areas, re-welds, sanded spots, handling damage and other defects.

Pros – cheap, fast, least labor intensive, little skill required

Cons – not visually appealing on a class A part, visual “halo” around repair, repair is not as durable as the rest of finish, repair may fade or chalk faster than surrounding powder coated finish

Usable with most decorative finishes. This repair method is fine except for on the primary surface a customer can see.

Re-coating

In some instances, your powder process can allow for a repainted finish to go over a previously painted part with no prep work. Usually the part must be freshly powder coated with no contamination on the surface.

Some chemistry is not compatible with this method and the surface will need to be abraded (blasted with abrasive grit or scuffed with sandpaper) and then wiped down with alcohol. If the part has been cured for more than a week, it will almost always need to be abraded and cleaned before re-coating. 

Pros – Less expensive and faster than stripping, better corrosion protection than liquid enamel

Cons – Adhesion risk (always do a test part and check adhesion), too much film build-up could cause issues (weight, measurement tolerances, extreme temperature checking)

Many small parts manufacturers will re-run parts after inspection if they have light powder coverage or other easily repaired surface defects. In the closet hardware and racking industries it is especially common for facilities to repaint parts once or twice if they are having an acceptable amount of rejects.

Tip: Remember to use your powder gun’s re-coat settings to properly apply a second coat

Sanding And Buffing

Sanding and buffing the powder finish can eliminate surface trash and some defects. This also helps smooth out orange peel that naturally occurs with most powder coatings on parts where the powder thickness is excessive in a particular area. Sanding companies like 3M have a series of abrasive and buffing compounds that allow shops to sand out defects and then bring the surface back to a smooth shine.

Pro’s – Mirror-like finish, faster to buff than to repaint

Con’s – Burn-throughs will need to be repainted or touched up with a liquid paint, labor-intensive, requires moderate skill

In the automotive and other transportation industries, manufacturers will sometimes sand and buff out Class A type parts such as hoods or panels that need to have a mirror-like defect free finish. This is similar to work done with wet paint. It takes some experimentation to develop a successful sanding and buffing process.

Tip: The sooner you buff after curing, the easier it is to work with the finish. Power coating gets very hard 1-3 days after curing.

IMPORTANT! Be sure to have the buffing operation isolated from the finishing operation. Many of the waxes and compounds used for buffing and polishing do not react well with painting and powder coating processes and can cause defects like “fish-eyes.”

 Fillers And Putties

There are many products like Bondo and Lab-metal that can be used to fill gaps and seal holes prior to powder coating. Before adding a filler to your process, make sure it is compatible with 400° to 450° F curing temperatures and that it is recommended for powder coating.

Pros – Eliminates re-welding for small areas, surface defects are much less noticeable if repaired prior to powder coating, parts do not need to be taken off-line for repair

Cons – Powder may have trouble being electrostatically attracted to the repair, in a large area adhesion can be suspect, may cause powder finish to “shimmer” or look different over repair

Trailer companies often use filler-putty to bridge gaps in their dump-style trailers. Tiger Drylac has a two-component filler that has some conductive elements for good results when used under a powder coated finish. Here is a link to their data sheet:

http://www.tiger-coatings.us/fileadmin/user_upload/downloads_us_new/product-data-sheets/tiger-drylac/special-products/Epo_Strong_Series_93-70080_Epoxy_Repair_Kit.pdf

Total Strip And Repaint

If there is a catastrophic finish failure, starting over after taking the finish off down to the bare metal can sometimes be the only solution. Major powder coating issues, like severe adhesion problems in high-performance parts, often require a total repaint. Pretreatment failures, parts contamination after pretreatment, underbaking, and overbaking can also cause problems that are so bad that the only answer is to totally strip the coating off and redo the process (after you have identified and corrected the fault in the process). Remember, the finish is only as strong as its weakest layer, so if you notice flaking once the finish is cured, it will need to be completely redone.

Pros – Once the process is fixed, you have high quality parts going to the customer and you don’t have to worry about field failures and the possibility of costly claims in the future

Cons – Costliest and most time-consuming solution

For demanding projects like government contracts, high-performance industrial components, engine parts, military equipment, parts that will be exposed to a highly corrosive environment or impact/abrasion in the field, the only way to insure quality compliance for parts that have badly defective finishes is to re-work the parts down to the metal.

The Nail Polish Fix

We’ve just outlined the most common touch-up and re-work methods, but there is another technique that can sometimes get positive results. An uncommon method for fixing small finish imperfections is to put a small amount of the powder in a clear lacquer and use it as touch-up paint. It’s possible to use hair spray, nail polish and other lacquers in a hobby situation, but bulk materials will be needed in a professional environment. Although the touched-up area will visually match the cured powder paint, the repaired area will not have the same durability as the cured surface. Remember, if you need the same surface integrity and durability in your touch-up areas as you do with the powder coated finish, you will probably need to use a two-component catalyzed topcoat and possibly a zinc-rich epoxy primer for appropriate corrosion resistance.

Meet Expectations With The Right Powder Coated Finish

To retain business and keep customers happy, you need to know exactly what each customer expects from the powder coated finish you are providing. Once you know that, you can develop a process that includes a repeatable touch-up system that addresses defective finishes of all types. Proper touch-up and re-work techniques help ensure great finished products.

Using professional quality equipment can solve many of your coating issues, including overbake and underbake problems associated with outdated or inferior quality ovens. All of Reliant Finishing Systems’ equipment is designed to provide the best finishes possible for today’s powder coating operations. Find out more about Reliant equipment here, or give one of our systems specialists a call today.

Understanding Powder Coating Gun Settings

When you first start powder coating, adjusting your powder coating gun settings can be confusing. We’ll cover the most important terms and settings for everyday powder coating situations and addresses some common issues you may encounter. Once you understand how electrostatic powder guns work and know what the basic gun settings do, you can improve your powder coating results quickly and confidently.

Author’s Note: All examples in this article use the Wagner EPG controller for illustrative purposes, but other brand-name professional quality guns have similar controls.

Powder Coating Gun Settings # 1: Kilovoltage (kV)

Powder Coating Gun kV Meter“kV” is the symbol for kilovolt. One kilovolt = 1000 volts. It is a unit of measure indicating how much electrical charge an electrostatic powder gun can produce.

The kV adjustment changes the amount of voltage charging the powder particles as they pass through the gun. The higher the setting, the stronger the charge. High settings are great for flat panels and the outside of box-like parts. A high kV setting can improve your transfer efficiency (more powder sticks to the part) and also allow you to increase the distance between the gun and the part. This can help you get very uniform coverage on flat surfaces. In some cases, excessively high kV settings can cause tiny pits or dimples in the finish due to “back-ionization.”

Lower kV settings are best for Faraday cage areas and when working with some specialty powders, such as metallics. As a general rule, the more detailed and complex the part, the lower the kV setting. Professional quality powder guns from companies like Gema, Nordson and Wagner typically have a maximum voltage setting of 100 kV. A good starting point is a setting of 50 to 80 kV for applying a single coat (or the first coat) to an uncoated part. When working with Faraday cage areas, turn down the voltage. When applying a second coat, a lower kV setting can give the best results.

What is the Faraday Cage effect? This describes what happens when you are trying to powder coat into a recessed area like the inside of a box. Highly charged powder particles are attracted to the closest grounded metal surface–the sides of the box–so they have a difficult time penetrating into the corner. This often happens with parts that have tight corners, angled features, prominent bends or recessed areas. Window and door trim, frames, boxes, wire racks, I-beam sections, angle iron, conical parts, u-shaped channels, uni-strut, grids, and other unusually shaped parts can be tough to coat without adjusting the gun’s output. By reducing the electrical charge (lowering the kV setting), you can help sprayed powder penetrate Faraday cage areas more effectively.

It is important to have a good ground. This is the physical connection that allows an electrical current to follow a path to earth. A ground is needed for the charged powder particles to effectively be drawn to the metal part. The stronger the ground, the more effectively the electrostatic process works. We recommend the use of a dedicated grounding rod. Get a copper grounding rod of at least 8’ length from an electrical supply company. Drive the grounding rod into a spot as close to your powder spray booth as possible (yes, you will have to penetrate your concrete floor if you have one). Using a good quality grounding strap of 14 gauge or heavier wire (heavier is better) and a well-made clamp, connect the ground rod to the rack or hook that is supporting your part. This will dramatically improve the performance of your coating gun, especially when dealing with complex parts. In some areas, you may need to pour a few ounces of water into the hole around the grounding rod to improve the quality of your ground.

Another way to improve results in Faraday cage areas is to aim the gun near the corner or detail area, but not directly at it. Wrap is the term that describes when sprayed powder is attracted to the back side of the part. Wrap means that the gun delivers powder to areas of the part that aren’t directly in front of the gun’s output. By having a good quality ground, you can get improved wrap on panel-shaped parts and improved penetration into Faraday cage areas.

Remember, voltage and amperage are not the same thing, so it may be important to also adjust the amperage at which the powder is being sprayed.

Powder Coating Gun Settings #2: Microamperage (µA)

Powder Coating Gun Microamperage Meter“µA” is the symbol for microampere. One microampere = 1/1,000,000th of an ampere. It is a measurement of electrical current. It indicates how much charge is moving from the gun’s electrode to the cloud of air and powder exiting the gun, and then onto the surface of the part being coated. This may be the hardest gun feature to understand.

Voltage and current (measured in microamperes) have an inverse relationship when you’re talking about powder coating guns. Voltage is a measurement of electrical “potential to do work,” while current is a measurement of the actual movement of electricity–“the work being done.” When some of the potential energy is used, it becomes current. As current increased, there is less potential (unused energy) left. A gun’s current feedback system can indicate to the operator what the electrostatic charge is doing. It is, in some ways, more useful than just looking at the kV setting. This is because the microamperage reading tells you how much of the charge is working, instead of just indicating the charge’s maximum potential like the kV setting does. On powder guns like the one shown from Wagner, you can see the effectiveness of the charge and limit how much current is possible. This allows you to understand and control how much energy is being used.

The kV setting is, in part, restricted by the power supply. While spraying a part, the load on the power supply limits the actual output, so the voltage may be lower than the setting. The current load increases as the gun gets closer to the part being sprayed. On a gun with an adjustable current limiter, when the current load reaches the set limit, the kV will quickly decrease. This helps prevent problems from too much voltage (like dimples in the coating from back-ionization), especially when the gun is too close to the part. Also, if the amperage is not limited to a certain range, the transfer efficiency may suffer in Faraday cage areas or the powder may not coat evenly if the gun-to-part distance is inconsistent. Setting the µA range to 20-25 can help with difficult to coat areas.

Powder Coating Gun Settings #3: Air-Flow/Powder Volume Dial

Powder Coating Gun Air-Flow DialWagner powder application guns automatically balance the powder output with the airflow via the main dial. The number selected is the actual maximum percentage of powder that can be used. Typically, 70% is the highest you would want to go. When working with intricate parts, this number can be much lower.

 

 

Powder Coating Gun Settings #4: The Factory Presets

Powder Coating Gun Factory PresetsThese are settings pre-determined by the gun manufacturer or the operator. They are intended for the most common scenarios encountered by typical gun users.

Flat Panel Setting: This setting provides maximum kVs and a high volume of powder being sprayed. This is for large flat panels and will provide a lot of powder wrap.

Repaint Setting: This setting is for a previously painted part that needs more powder for cosmetic or performance reasons. The kVs are reduced, as is the powder volume, since there is already powder on the part.

Faraday Cage Setting: This setting lowers the kVs, restricts current µAs, and reduces the powder flow percentage to allow powder to penetrate difficult-to-reach corners and angles.

Custom Settings: These are the settings that you use with a specific powder or part. The fourth preset is reserved for custom settings. (On the Wagner controller, you have up to 50 available custom settings that can be saved.)

My Powder Coating Gun Is Set, Now What?

Once you’ve got your powder gun adjusted correctly, you are ready to start spraying powder. Before you begin coating a part, look at the part and figure out how you will get the best and most efficient coverage while spraying. As your part becomes coated with powder, a charge will build up on the surface. It will make the Faraday areas even more challenging to coat. Therefore, it is best to coat the Faraday areas first, then spray the flat surfaces of the part.

After rehearsing what you are going to do, you need to get the powder flowing smoothly through your gun. Spray the powder coating gun away from the part until a uniform cloud is coming out with no sputtering or surging. This may take up to a second or two. Move the gun to the part and move it in a slow, controlled motion across the part, keeping a gun-to-part distance of around 8”. Keep the gun triggered and spraying until the part is done—don’t start and stop. If possible, try to get full coverage with a single pass across the entire part. Often you will need to move the gun in a controlled back-and-forth motion, starting with side-to-side movements and then switching to up-and-down passes if needed.

Inspect the coated part with a bright light to help detect thin spots. Touch up any spots you see before curing the part, but be careful not to add too much powder or to let the gun puff powder onto the touch-up areas. These common mistakes happen when you become impatient and blast the part with a heavy fog of powder or don’t let the gun’s powder flow stabilize before attempting touch-up work.

What Else Do I Need To Know?

Air Supply Problems are not uncommon. It is critical that you use only cool, dry, oil-free compressed air to power your powder application guns. Make sure you have an accurate in-line pressure gauge and a regulator that can restrict the amount of pressure reaching your gun. You may need to use a powered air dryer, and you will definitely need a filter system that traps moisture and oil.

Fluidization is what we call the small amount of air movement that aerates and fluffs the powder around the pick-up tube on a box-feed unit. An adjustable valve controls how much air is provided. The air helps break up clumps of powder before they are pulled into the pick-up tube and pumped through the gun. It is also the term used for the air movement that mixes the powder in a hopper container. In the hopper unit, there is a plastic membrane at the bottom with lots of tiny holes that allow the air to condition the powder. When adjusted correctly, it will look like the powder is slowly boiling.

Impact Fusion describes what happens when partially gelled powder sticks to sharp areas in the gun and inside the powder pump. This problem is more prominent in hot shop environments and when working with poorly conditioned powder. The stuck-on powder can be removed with a clean, fresh shop towel and denatured alcohol.

Mil Thickness is the term used when talking about the thickness of the powder coating material that has been cured over the surface of a part. One mil = 1/1,000th of an inch. A healthy human hair is about one mil thick. Most powder coated finishes are between 2 and 4 mils thick, with some finishes up to 6 mils or thicker. Achieving ideal powder thickness and uniform coverage takes practice. Make sure to keep good notes. Some coating instructors have their students spray test parts to learn about adequate powder coverage. A student sprays a part while the instructor illuminates the surface of the part with a bright pocket flashlight. Once the flashlight no longer reveals any bare metal spots, the student stops spraying. This method typically results in a finished coating that is about 2 mils thick.

Orange Peel describes the uneven, “wrinkled” finish that can happen after curing if the painter sprays too much powder on the part in some places. You can end up with areas of heavily concentrated powder that flow out into wavy sections that have something of an orange peel texture. The excessively thick powder in these areas will also make the finish more prone to chipping. If the applied powder is under-cured, especially as the result of the oven temperature being too low, the powder can also fail to flow out properly, even if it’s not too thick, causing the same type of textured defect in the finish.

Powder “Starved” Finish/Light Powder are terms used to describe the grainy texture that a defective finish can have after it is cured if the part does not get adequate powder coverage. If there wasn’t enough powder on the part for it to flow together and create a uniform coating, it can have an odd, textured appearance. Even worse, the part will likely start to rust or oxidize in these textured areas because the part’s surface isn’t fully covered by the coating material. Using a powerful flashlight or LED inspection tool can help prevent this by allowing the painter to see areas that need more powder.

A professional powder coating gun can make a huge positive impact on your operation, allowing you to coat with more accuracy, better efficiency and higher quality. Reliant Finishing Systems only offers professional powder guns from companies like Wagner. Need a new powder application gun or a complete powder coating system? Our powder coating specialists are ready to help – give us a call today!

The Basics Of Powder Coating Coverage

Powder Coating Gun And PartKnowing how much powder you need for a particular job is critical when determining cost. Without that information, it is easy to make pricing mistakes that can drain your profits or run off potential clients due to pricing that isn’t competitive.

However, calculating powder cost can be a little confusing. We’re going to show you how to calculate powder coating coverage and how to gather the information necessary to give an accurate prediction of cost per square foot.

 

The Data You Need To Calculate Powder Coating Coverage

Before you start calculating coverage costs, these are the values that you will need to know :

  • Powder Specific Gravity
  • Cost Per Pound of Powder
  • Transfer Efficiency
  • Dry Film Thickness
  • Square Footage of Metal To Be Coated (Per Part)

Powder Specific Gravity: This is usually supplied by the powder coating manufacturer on their technical data sheet. Remember that not all powders of the same color have the same specific gravity.

Cost Per Pound of Powder: Check your invoice or get the cost from your powder manufacturer or sales representative.

Transfer Efficiency: Transfer efficiency is the percentage of the powder that is being applied to the part instead of being wasted as overspray. Transfer efficiency is almost always an estimated figure and the most difficult one to determine when estimating coverage costs. It is hard to get an accurate percentage of how much powder is being applied to the part and how much is going in the filters, on the floor, on the rack, and getting stuck to the booth’s walls.

Powder Coating Gun Overspray

Transfer efficiency is directly impacted by how much powder the operator is using.

Transfer efficiency is directly related to the way the operator is applying the powder. If there is a giant cloud of powder in the booth or a heavy fog of powder blasting out of the gun, you can bet that there is more wasted powder than if the operator is spraying lightly enough to coat the face of the part and still get a gentle wrap of powder moving around the part to partially coat the other side.

Proper ground and powder coating gun quality can have a significant effect on transfer efficiency. A shop with a dedicated ground rod that is connected to the parts rack or hooks, or to an uncoated portion of the parts, can always get better transfer than one that doesn’t. Likewise, a shop using a professional quality electrostatic gun with adjustments for powder flow, voltage and current can get better results than one using a hobby gun.

For estimation purposes, if this is a new operation with untrained painters, the transfer efficiency can be as low as 25%-30%. After proper instruction, experience, gun adjustment, and proper ground, the transfer efficiency can reach 70%. If you are reclaiming the powder by collecting and reusing the powder, you could possibly reach 85%.

One way to calculate transfer efficiency percentage is to determine how much powder is applied to a part in the time necessary to fully coat that part. You will need a high quality digital scale and a timer to do this. First, weigh your part before you spray it. Get your timer ready and spray the part until it is fully coated and ready to cure. Record the time it took to coat. Now, weigh the part again to learn how much powder was deposited. Next, turn off the gun electrostatics but do not adjust the powder flow or air and spray the powder gun into a porous filter bag that will trap the powder but allow the air to flow through (you can get these online or from your powder supplier). Spray powder for the same length of time it took to spray the part. Weigh the bag before and after to measure how much powder was applied. Then apply the following formula:

Powder Deposited (the weight of the powder on the part) divided by Powder Applied (the weight of the powder in the bag) multiplied by 100 will give you the basic transfer efficiency percentage.

Powder Coating Gun Applying PowderDry Film Thickness: This is the amount of powder you would like to apply to the part, measured in terms of coating thickness. You can measure a part with a DFT gauge to get an average of the mil thickness across a section of the part’s surface. You should take as many readings as possible, then average them, to get the most accurate estimate of the overall average thickness.

Square Footage of Metal in Your Part: This might take a bit of calculation but it will give you the cost per part at the end of this exercise.

Powder Coating Coverage Formula

Now that you have all the data you need, you can apply the powder coating coverage formula.

Assumption: The Powder Coating Industry standard is 192.3 square feet of coverage per pound of powder. This pound of powder would be at 1.0 specific gravity and applied at a thickness of 1 mil with 100% transfer efficiency. In other words, this is how much surface a common powder could cover if no powder was wasted and you only needed a thickness of 1/1000th of an inch.

So the formula would be:

Actual Coverage Rate (ACR) = 192.3/Specific Gravity/Mils x Transfer Efficiency (as a decimal)

Example: Powder A has a 1.5 specific gravity and is being sprayed at 2 mils with 50% transfer efficiency. The powder cost is $5.00 per pound. The part being sprayed has 3 square feet of surface area.

ACR = 192.3/1.5 (specific gravity)/2 (mil thickness) x .50 (transfer efficiency)

ACR = 32.05 square feet per pound of Powder A

Next, take your cost per pound and divide it by your ACR.

Cost per square foot = $5.00 (cost of one pound of powder)/32.05(ACR) = cost is $0.16 per square foot of coverage by Powder A

Multiply this cost by the square footage of your part’s surface area and you’ll know the cost of the applied powder.

Cost Per Part = 3 (square feet of part) x $0.16 (cost per square foot) = $0.48 per part in powder cost

Now that you know how to do this by hand, Interpon has a nice online calculator that you can use here: http://www.interpon.us/our-coatings/powder-coverage-calculator/

Knowing what your cost is for powder coverage will prevent you from making costly budgeting mistakes and keep your prices competitive.

Powder Coating Gun For All ApplicationsIn order to maximize your profits you have to maximize your transfer efficiency, and the best transfer efficiency comes from professional powder coating guns. Professional guns provide multiple settings and factory-presets to get the right amount of powder onto your parts without excessive waste. Reliant Finishing Systems only provides professional quality powder application guns from industry-leading companies like Wagner. When you buy from Reliant, you know you’ll be getting the gun you need to get the job done right.

Looking for a new powder coating gun or new powder coating system? Give us a call today – our systems specialists are standing by to answer your questions and help improve your operation.

Manual Powder Coating Gun Comparison: Box-Fed vs Hopper-Fed

Venturi Pump - Wagner Manual Powder Coating Gun

Typical venturi pump from a Wagner manual powder coating gun system.

If you’ve been shopping for a manual powder coating gun, you’ve already seen the terms “box-fed” and “hopper-fed.” In this article, we’ll explain what those terms mean, how they affect your powder coating process and how picking the right gun configuration can dramatically improve your results.

Every professional quality manual powder coating gun has an integrated delivery system for preparing the powder and bringing a steady stream to the application gun. The powder flows through the hand-held application gun as it is sprayed onto the part being coated. Both box-fed and hopper-fed delivery systems provide powder to a venturi-type powder pump, but these two preparatory feed systems have different attributes. You’ll need to consider which system will work best for you before buying a new powder coating gun.

[Author’s note: We’re showing Wagner products for this article, but other brands look very similar.]

Box-Fed Powder Coating Guns

Wagner Box-Fed Manual Powder Coating Gun

Wagner box-fed powder gun with pick-up tube shown outside of a box of powder.

A box-fed powder coating gun draws powder coating media directly from the box provided by the powder supplier. A platform holds the powder box at an angle on a stand below the gun’s controls. A powder pick-up tube is then inserted into the powder in the box. The pick-up tube hangs vertically and usually has a small amount of compressed air delivered to the tip area to break up any compacted or clumpy powder. This helps assure uniform powder flow. The tube routes the powder up to the venturi powder pump, which sends the powder to the gun itself.

During operation, the platform which holds the box constantly vibrates. This vibration causes the powder to shift around inside the box. The powder in the box moves constantly and replaces the powder that is being pulled up the tube. This prevents “rat holes” from developing in the powder still in the box. Without constant vibration, the powder would be supplied in surges, which would create problems during application and degrade the finish.

Advantages of Box-Fed Powder Coating Guns

1) Fast Start-Up: Grab a box, open it up, put the pick-up tube in and start coating!

2) Quick Color Change: It takes as little as 3-5 minutes to change colors when using a box-fed gun with air pulse cleaning. Less expensive models may require up to about 10 minutes. You simply clean or swap the hoses, switch to a different box of powder and go back to work.

3) Lower Initial Investment: If you spray a variety of colors and textures each week, the cost of buying multiple hoppers can really add up. Since the powder you buy already comes in a box, there is no extra cost associated with dealing with lots of different powders.

4) More Mobile: There’s less weight to move around your shop when working with a box instead of a hopper on the gun cart.

Disadvantages of a Box-Fed Powder Coating Gun

1) Special Effect Powders Won’t Work: Since the vibratory box feed system tends to cause larger or denser particles to settle to the bottom of the box, any powder that has distinct particle size differences can have consistency issues, especially as you get closer to the end of the box.

2) Humidity Can Cause Problems:  To get best results and prevent powder from degrading while in storage, you should keep your powder in a cool, dry, climate-controlled area. If you are starting a new project and you bring powder into a hot and humid shop environment, you can encounter troublesome powder clumping due to condensation occurring when the cool powder is exposed to the humid air.

IMPORTANT:  When working in hot or humid environments, bring out a box of powder a couple of hours before you need it and open the top to allow the powder to acclimatize to the environment before you start spraying with it.

3) Spillage And Contamination: Although it isn’t easy to do, you can tilt the gun cart by accident and spill the powder out of the box. You can also get contaminants in the powder if you try to reuse spilled powder, or if you have a dirty shop environment and leave the opened box of powder in use for a long period of time.

Hopper-Fed Powder Coating Guns

Powder Coating Gun - Wagner Hopper Fed Gun

Wagner hopper-fed powder gun with powder pump attached to a 60-liter stainless steel hopper.

A hopper-fed powder coating gun holds the powder in a sealed (usually stainless steel) container that has a perforated plastic membrane on the bottom. This membrane has tiny holes in it that allow compressed air to enter the container and constantly fluff the powder so that it flows around inside the hopper. This process is called fluidization. When you look at the top surface of the powder in a hopper that is being fluidized by compressed air, it should look like it is boiling. If you put your hand in the powder while it is being fluidized, it should feel silky smooth.

The compressed air supply to the hopper should be adjusted so that powder isn’t wasted due to excessive agitation/over-pressurization of the container. While some powders require a small amount of venting, you should adjust your system for minimal powder loss, especially if you are reclaiming the powder as an on-going process.

Specific Advantages of Hopper-Fed Powder Application Guns

1) Conditions The Powder: The fluidization process helps remove moisture in humid environments by introducing clean, dry air from the bottom of the hopper.

IMPORTANT: Never stir the hopper with a stick! It can damage the plastic membrane on the bottom of the hopper, reducing the effectiveness of the fluidization airflow.

2) Mixes The Powder: Fluidization also insures that the powder is thoroughly mixed. This is important if you are regularly spraying river textures or bonded metallic powders, or making a transition from one batch of the same powder to the next.

3) Less Chance of Powder Contamination: The hopper is sealed off from the surrounding environment and each hopper is typically used for only one type of powder.

4) Less Surging: Because the powder is better conditioned, the pump picks up the powder more consistently and the gun delivers it more uniformly.

Disadvantages of Hopper-Fed Coating Guns

1) Increased Cleaning Time: If you have only one or two hoppers for all of your colors and textures, it can take a significant amount of time to switch between colors or textures—up to one hour per change if done meticulously.

2) Cost/Storage Issues: If you buy multiple hoppers to accommodate all of your most commonly sprayed powders, it can be costly. It can also be challenging to store hoppers when they are not in use. You may end up using valuable floor space to store empty hoppers, particularly if you don’t normally carry some common powders in inventory and get them on demand from your powder vendor.

3) Reduced Throughput: If you commonly have to move the cart around a good bit because of the size or complexity of what you are coating, having a hopper-fed gun can slow you down. A gun cart loaded with a full 60-liter hopper (the most popular size) can be a bit unwieldy.

Which Powder Coating Gun Is Right For You?

Depending on your work environment, getting the right configuration can make a significant impact on your performance. If speed (how fast you can get started on a new project), agility (how fast you can change colors or textures) and lower cost are key concerns, a box-fed gun may be the right choice for you. If premium finish quality is the most important goal, a hopper-fed gun is probably the right tool for the job.

Box-fed powder coating guns are best suited for:

1) Job Shops: If you spray different powders for different jobs, guns that are box-fed let you change colors quickly between projects.

2) Regular Powder: If you don’t do a lot of special effects, box-fed guns work fine with most single color powders.

3) Small Powder Runs: If you only powder coat a small number of parts the same color during the week, a box-fed unit is perfect for projects where you’ll only be running a few pounds of a specific powder at a time.

Hopper-fed powder guns are recommended for:

1) Limited Color Applications: If you only use a handful of different powders, a hopper-fed gun is usually a better value.

2) Special Effects: As noted before, if a special effect powders are an important component of your process, having a hopper dedicated to each of these powders would be best. Special effect powder must remain fluidized to be applied properly, and a box-fed system simply won’t cut it if you need professional quality results.

3) Reclaim: If you reclaim your powder, you’ll need a hopper-fed gun. The hopper-fed system enables you to mix reclaimed powder with new virgin powder perfectly.

IMPORTANT – If you are new to reclaiming spent powder, a ratio of 60% virgin to 40% reclaimed powder is a good starting point.

4) Humidity Issues: If your powder’s characteristics or your shop environment causes clumping due to humidity, using fluidized hoppers will usually cure this issue if you have an air dryer attached to your shop’s compressed air supply.

With either feed system, you can be successful powder coating a wide range of substrates with multiple types of powders. If you decide on a box-fed system first, you can always add a hopper later. With most professional quality systems, a hopper can be attached right to the box feed controller and only requires a small fluidizing air tube attachment. Although it may cost a little more to have your gun configured this way, it enables a single gun to give you the benefits of both systems.

Have questions about powder coating guns? Looking to add a new gun to your existing coating operation? Feel free to give us a call. Our systems specialists will be happy to help you get the powder coating gun you need.

Using Iron Phosphate To Get A Better Powder Coated Finish

Pic for steam unit pageWe’ve talked a lot about pretreatment in previous articles: why it’s important to get your parts clean and what pretreatment options you have. But from a production standpoint, why is pretreatment important? Why add another step to your powder coating process? We’ll examine this using one of the most commonly powder coated materials: steel.

If you are powder coating, chances are that at some point you’ll be powder coating steel. Powder is easily applied to steel parts and generally provides a good finish. But what if you need the powder coating on your steel parts to last longer or to be more wear-resistant? You may be providing parts that will be subject to high-impact or are handled regularly, or parts that must last a certain amount of time. Simply applying the powder and curing the part won’t achieve the result you or your customers need. In order to get those results, you’ll need to add a pretreatment step before you apply the powder.

One of the most popular and effective forms of pretreatment for steel is iron phosphate. Iron phosphate is a conversion coating that provides a barrier against oxidation. It is most effective on bare (uncoated), clean steel.

How Can Iron Phosphate Improve My Powder Coated Finish?

Adding an iron phosphate stage to your pretreatment can dramatically improve the quality and longevity of your powder coating.

Iron phosphate provides increased adhesion. This is especially useful for slick surfaces. Iron phosphate pretreatment causes a small amount of surface material to be deposited on the parts being treated. This material is slightly textured so the powder can grip it. If the parts are occasionally bumped during their use, this improved adhesion is especially helpful because it keeps the coating intact.

Iron phosphate provides increased corrosion resistance. Most powders provide a salt-spray rating of 250 hours on clean metal, but what happens when the protective powder coating is scratched or worn? Phosphate adds a second layer of protection and can extend the salt-spray rating to 500-1500 hours, depending on the process.

How Can Iron Phosphate Be Applied?

There are a number of different ways to apply iron phosphate to your parts before you apply the powder coating.

Hand wipe: While not very efficient or consistent, there are chemicals that can be hand wiped on and then rinsed off to form an iron phosphate layer.

Hand spray: Professional quality wand systems, also known as spray wands, are very good at delivering iron phosphate chemicals to the surface of most parts. Iron phosphate works well with heat, so gas fueled or electrically heated sprayers work best. These sprayers may include pressure wash, wet steam or dry steam features. A rinse/seal step is often required as part of the process to prevent streaking or chalking that can interfere with the powder coating. Spraying is often done inside a stainless steel booth, often called a manual wash station, and/or may take place over top of a grated wash stage that allows spent chemistry to be contained and potentially recycled.

You can see a hand-operated spray wand in the video by Electro-steam below:

Dip: Heated chemical vats, also known as dip tanks, are a great way to pretreat baskets of small parts that have hard to reach areas. This often involves multiple stages performed in a series of tanks with rinse stages in between.

Automatic spray: This is generally the most effective and consistent way to apply iron phosphate chemistry, but it is also the most expensive. Multi-stage spray systems are typically part of an automated coating line where the parts travel by conveyor at a pre-set rate. A multiple stage pretreatment system can have as few as 2 stages or as many as 8 or more stages. For higher-end architectural finishes, multiple applications of phosphate create an excellent corrosion barrier and other agents in the chemistry clean the part to allow for nearly defect-free parts when powder coating is applied.

Where Can I Find An Iron Phosphate Supplier?

Search online for companies like Bulk Chemicals, Chemetall, Dubois, or Houghton. These companies and others can provide you with information about local suppliers or will have a local distributor contact you to help you select the proper chemicals.

Your local powder supplier can suggest a chemical supplier who will have products that work well with the powders you are using.

Thomas Register & related industry guides may also be able to provide you with an iron phosphate supplier. You can get a lot of information from industry guides like Thomasnet.com, but you may have to play around with your search settings to find companies that will do business on a smaller scale.

As a general rule, avoid online outlets that cater to the hobbyist and DIY markets. They may have chemical products of inferior quality or from sources that vary from batch to batch. Parts preparation is one of the most important steps in the coating process—don’t risk costly reworks by using cheap, no-name chemistry sold online by the bucket.

Have any questions on pretreatment? Need to add pretreatment to your powder coating operation? Reliant provides blast rooms and wash stations for use with your existing equipment, or we can implement your pretreatment requirements into the design of your new coating system. Whatever you need, from hand-wash spray units to fully automated wash stations, Reliant Finishing Systems can provide a quality system at an unbeatable price. Call one of our system specialists today to get started.

 

How A Powder Coating Oven Recorder Can Help Solve Your Curing Problems

Powder Coating ovens from Reliant Finishing SystemsWhether you’re just starting to powder coat or your powder line has been operational for years, you need to have an accurate picture of what’s going on inside your curing oven if you want the best results. Fortunately, there are a number of maintenance and troubleshooting tools available to help get the best finishes possible from your coating equipment. One of these tools is a powder coating oven recorder, also known as an oven data recorder, which can help identify curing problems, increase your throughput, and optimize your oven’s fuel efficiency.

When Should I Use A Powder Coating Oven Recorder?

When first starting to powder coat, it is a good idea to run an oven data recorder to determine exactly how fast your metal parts reach the proper powder curing temperature. This is important because powder companies formulate their powder to cure with specific metal temperatures and curing cycles in mind.

Depending on your market and your customer’s specifications, you may want to run a powder coating oven recorder whenever you add a new type of powder to your process. You may also want to check the oven’s performance if you are working with parts that are much heavier, thinner, larger or smaller than usual, or made of a different material (such as swapping to aluminum from steel). This is especially important if your customer has stringent finish requirements.

Identifying Powder Over-Bake and Under-Bake

The primary reason for checking your metal temperatures is to make sure you are not over-baking or under-baking your powder. Over-baking usually refers to curing the powder at higher than recommended temperatures, while under-baking means the opposite. These terms are also used when talking about the amount of time that the part surface is at curing temperature. Too long can cause over-baking and too little can result in under-baking.

Over-baking powder can lead to brittleness, flaking, discoloration (yellowing or browning), and lack of gloss. Under-baking powder can cause excessive orange peel, poor chemical resistance, lack of adhesion, inconsistent gloss, and poor resistance to corrosion. If your powder is exhibiting any of these problems, it may indicate that your oven is getting too hot or not getting hot enough. An oven recorder can help identify if your oven temperature (https://www.reliantfinishingsystems.com/powder-coating-equipment/powder-coating-ovens/) is not reaching the desired range or if there are hot spots or cold spots in the cabin that are impacting your curing results. If the temperature in the oven is not within the necessary range, or it is significantly inconsistent inside the cabin, you’ll end up dealing with curing problems even if they are not immediately detectable. A high quality powder coating oven recorder is the best tool to use when you need to identify those issues.

Understanding An Oven Data Recorder Report

There are a number of oven recorders on the market, but the most well-known brand used in the finishing industry is Datapaq. Their oven reporting software is what we will be referencing for this article. Here is a typical Datapaq graph and printed report:

Powder Coating Oven Recorder Report - Graph

Powder Coating Oven Report - Technical Readout
That is a typical report from a walk-in size batch powder coating oven from Reliant Finishing Systems. The first thing to look at is the graph itself:

Powder Coating Oven Recorder Report - Graph Close-up
The top red line shows the air temperature probe, which measures the air temperature of the oven at a specific location, usually near the part being tested. At arrow A, the air temperature rises to the 425° F set point (the temperature that the operator wants the oven to reach) and then starts idling at +/- 5 degrees. This consistent discharge of heated air allows the metal temperatures, arrow B, to rise evenly to the desired curing temperature.

If you notice dips in the air temperature line, these represent potential problems that can hurt your throughput by increasing cure times, and may reduce your overall finish quality. This is because undesired drops in air temperature may decrease the consistency of the surface temperature of the part.

The opposite problem, spikes in the air temperature, can be just as bad. Whenever your oven’s heat system overshoots the temperature you want, you’re wasting fuel. You can also end up damaging finishes that require a delicate touch. By not recognizing the way excessive air temps influence your curing cycle, you’re also probably not operating at maximum throughput.

Some common causes of poor temperature regulation by the oven’s heat system include bad temp probes (thermocouples), insufficient insulation or insulation that has settled inside panels during shipment or handling, poor air circulation through the oven cabin, improper exhaust ventilation airflow, inadequate ducting, and faulty or outdated controls.

In batch operations, employees opening the oven randomly during the curing process to check the parts can dramatically affect the air temperature inside the oven and can lead to improper curing. Obviously, opening the doors lets out hot air but the rapid drop in temperature can also cause the oven’s heat system to go into overdrive getting the temperature back to the desired range. This wastes gas. Once the doors are closed again, the overshoot can cause the oven to overheat because the heat system cannot throttle back quickly enough once the hot air is no longer escaping from the cabin.

Using Your Oven Data Recorder On An Automated Line

When testing automatic coating lines, the powder coating oven recorder travels through the oven on the conveyor. It is not unusual to see temperature fluctuations around oven openings, during direction changes near the ends of multi-pass ovens or when the recorder gets close to the output of the heat system. Adjustments to air distribution baffles, plenum discharge dampers or exhaust intakes are typical when fine-tuning an automated line.

Here is an example of an automatic line test. This graph shows some serious temperature fluctuations:

Powder Coating Oven Recorder - Automated Line Test
Although not in color in this example, the two jagged top lines indicate the air temperatures measured as the recorder moved through the oven. The two smoother lines indicate metal temperatures. You can see how the abrupt drop in air temperature affects the metal temperature graphs. This can extend the dwell time needed in the oven, requiring a lower line speed for proper curing. Left unchanged, this can cause uncured parts to reach packing. A problem of this type with a conveyorized powder coating system may be due to a faulty burner in one of the heat units or perhaps a brief burner shut-down due to a safety switch tripping.

The powder coating oven recorder report gives you a couple charts showing the temperatures achieved and the time above these temperatures.

Powder Coating Oven Recorder - Automated Line Technical Readout

The arrow shows the cure time needed for the cure temperature specified. You can get this information from your powder supplier. The times circled are the metal parts’ time above the required curing temperature. Since these times are greater than the specified duration at the curing temperature, the parts should be fully cured when they exit the oven. If they do not reach the specified time at temperature, you’ll probably have to turn up the temperature of your oven or increase the dwell time.

Different metal thicknesses will affect your cure temperatures and times. If you are curing thin and thick parts at the same time using the same time/temp combination, you can possibly over-bake the thin parts–causing discoloration or reduction in gloss. Try to batch similar thicknesses of parts whenever possible. It’s also a good idea not to mix aluminum, stainless and mild steel parts if possible because they can have different curing characteristics. Even if you don’t use a data recorder, make sure you check the finishes you are getting with samples of all of your common parts when setting up your oven. Don’t let lack of attention to detail during set-up rob you of future profits.

When To Call In The Pros

Many powder providers will be glad to run a data recorder through your oven and share the information they discover. This allows them to help you get the best results from their products. It also gives them a chance to justifiably blame bad finishes on faulty or poorly calibrated equipment.

Larger production facilities and high-end job shops may have their own data recorders. These are usually stored and operated by finish line managers or facility maintenance technicians. In smaller shops, owners may have to request a line audit from a service company.

No matter who runs the data recorder, adjustments to the oven should usually be made by factory-authorized technicians. Shops with large coating lines may have in-house personnel trained to repair and adjust their ovens by the manufacturers or providers. That situation is uncommon, and most powder curing ovens are supported directly by the oven manufacturer, an equipment distributor or a specialized service company. When it comes to tuning your oven, we recommend that (whenever practical) you work with the company that built it.

Your powder coating oven should be started and calibrated by an experienced professional. Ideally, you should run some test parts with a data recorder early-on. After you’re in production, it is a good idea to check your oven quarterly or whenever you have a new part with significantly different thicknesses or geometry. A properly cured part is essential for your customers’ long-term satisfaction and will prevent costly returns and reworks.

Need your oven checked? Reliant Finishing Systems offers a wide array of services, including oven data recording, technical support, line audits and other troubleshooting services. Give us a call today.

Powder Coating Special Effects Can Give You Outstanding Results

Powder Coating Special Effects

Examples of powder coating special effects, provided by Espo’s Powder Coating.

As you know, powder can give you a more vibrant finish that lasts longer than traditional wet paint, and now it can rival wet paint’s ability to create jaw-dropping special effects. Many people, including coaters who have worked exclusively in a production environment, are sometimes unfamiliar with the effects that can be achieved with powder coating. In this article we’ll discuss some of the amazing powder coating special effects you can achieve with today’s powder coating technology.

Difference Between Powder Coating & Wet Paint Effects

While powder coating special effects are similar to wet paint, there are some key process differences between the two applications. Wet painters frequently use multiple layers of paint that are combined to create depth and brilliance. Liquid painters also use products that have specialized metallic or mica pigments to reflect light. These products can be applied in separate coating steps to create a custom look.

Powder coating special effects works in a similar fashion, but you have to cure, or at least partially cure, each powder layer before applying the next coat to achieve the correct results when attempting process special effects. Although this can be time consuming, you can get amazing results from multi-step effects like candy-coats and two-tone finishes.

Like certain wet paint products, there are powders that can create one-step special effects. Popular one-step effects include river textures, wrinkle textures, hammer-tone, veining, glimmer, and even holographic finishes. These one-step finishes just need to be applied carefully and evenly to your metal surface and then cured per the suppliers’ recommendations.

Process Powder Coating Special Effects

A process special effect is a special powder coated finish that can only be applied with multiple powder applications and curing steps. This includes candy colors and two-tone finishes.

Candy Colors, also known as candies: These products create finishes that have incredible depth and usually provide bright, dramatic colors. They are typically applied in 3 steps: a metallic primer provides the background, then a transparent but colored base coat is applied, and then a clear gloss topcoat completes the effect. Each coat is cured individually. The final clear is not always required, but will add durability and protection for exterior parts.

Prismatic Powders has a great example of a header done with one of their finishes here: http://www.prismaticpowders.com/gallery/detail/8296/Prismatic-Illusion-Violet-with-Clear- Vision-Top-Coat/

Two-Tone Finishes, also known as bi-tone or cut color:  A two-color finish that requires masking, and requires skill and patience to achieve the desired result. Masking a powder effect is challenging and you need to use high temperature tape in order to keep a clean line between colors. Using two colors that are intense and dramatically different will give you the best results because the second color coat usually has to cover the first coat. It can be done with some transparent coatings, but you will have to carefully plan your finish order. Like with anything you powder coat, doing small test pieces is always recommended before finishing large production pieces.

TIP: When removing high-temp masking tape, try to do it when the part is around 180° to 200°F. If you wait until it’s cooled down to room temperature it can leave flakes. If you pull it too early and the part is still near curing temperature it can pull strings of applied powder off of the surface of the part. A hand-held heat gun and a good quality IR thermometer (temp gun) can help with this custom technique by heating the part if it gets too cool and preventing damage to the finish.

Tom Esposito of Espo’s Powder Coating did a fantastic blending job using no tape to produce this custom frame finish: Powder coating special effects examples from Espo’s Powder Coating

One-Step Powder Coating Special Effects

As opposed to process effects, one-step effects are sprayed and cured just like conventional powder. All major powder manufacturers have special effect finishes that can be sprayed on in one step and then cured. The most common powder coating special effects are those that create textured finishes. Wrinkle and river are some of the terms used to describe the visual effects these powders create.

It is important to note that these powders must be mixed consistently to achieve consistent results. Conventional vibratory box guns are not as effective as hopper style guns that feature hoppers with fluidizing membranes. These hoppers constantly mix the powder with air, while vibratory box-fed guns may separate the heavier particles from the lighter ones due to agitation (think of the way gold panning works). Light textures usually work fine, but the heavier veining effect powders with multiple metallic or mica flakes can give disappointing results when sprayed from a box hooked to a vibratory gun system.

Vein/River Texture: Vein textures are quite dramatic and can give a unique look to your parts. They are often used for electronic enclosures, interior industrial applications, and many interior furniture components. Be careful selecting a vein for an outdoor application. Because of the nature of the veined powder, it can cause different finish thicknesses across the part and may compromise the salt-spray durability of the powder. Unless a texture effect powder product specifically states that it is for outside use, consider it as interior-use only.

Here is a Cardinal Powder chart that shows some different vein effect powders that are available: http://www.cardinalpaint.com/products/productcat.php?pcid=2&cctid=12

Metallics: True metallics come in two qualities: bonded and unbonded. Bonded metallics have a little bit of clear powder attached to the metallic powder particles and may be suitable for one-step interior applications. Unbonded metallics need to be coated again with a clear topcoat to protect the metallic particles from oxidization. Some bonded metallics also need an extra clear coat for exterior durability.

TIP: Metallic effect powders sometimes need different gun settings due to their conductivity. If you get weird patterns when spraying metallics, turn down your kV setting to the 20 to 40 range and see if that helps.

Micas: These specialty powders create finishes that look similar to metallics but are more pearlescent or opaque. They can be used on interior or exterior parts and are typically cheaper than the bonded metallic effect powders.

Hammer-Tones: These powders usually combine the river effects with pearlescent mica pigments. Consistent film thickness is important to maintaining a consistent hammered finish appearance.

As you can see, powder coated finishes can offer impressive custom looks. Modern powders can produce a wide range of special effects that can take your project to the next level.

Have you used any of these powder coating special effects before? Especially proud of your work? Even if you don’t use equipment from Reliant Finishing Systems, send your pics to info@reliantfinishingsystems.com so we can share your work with others who have an interest in powder effects.

You can also share them on our Facebook page at www.facebook.com/reliantfinishingystems

Getting the Right Blast Room For Your Operation

Blast Room Operator Cleaning Part For Powder Coating

Blast Room Operator Cleaning A Part For Powder Coating

There are a number of factors to consider when adding a blast room or abrasive blasting system to your powder coating or painting operation. No matter what type of dry blasting system you are considering, this guide is designed to help answer your questions and plan for your success.

Note: Although uncommon, wet blasting systems, also known as slurry blasting systems, are sometimes used. This article focuses on dry blasting systems, particularly those designed for manual blasting by one or more operators inside a walk-in size steel enclosure.

Part 1: The Blasting Enclosure

Before deciding on a blast room, it’s best to familiarize yourself with some of the features common across most manufacturers. Almost all blast rooms feature a square roof design instead of hip-style roofs. The square roof construction allows for more operator movement, easier load-in and load-out, and has better lighting. Light gauge hip roof models – which are often the cheapest on the market – may not provide the durability and usability you are looking for.

Wall and roof panels are usually available in thicknesses that range from 18 to 10 gauge or thicker. As a general rule, the heavier the wall thickness, the higher the cost. Everyone wants a heavy duty blast room, but heavier construction often offers no real benefit because high-wear areas are typically covered by rubberized shielding.

Blast rooms are commonly equipped with a moderate number of multi-tube fluorescent light fixtures and feature safety glass in order to meet code.

Upgrades To The Blasting Enclosure

While there isn’t much to upgrade when it comes to the cabin of conventional blast rooms, the door design is one area of the cabin’s construction where upgrades are typically worth the cost. The majority of professional-grade blast rooms include conventional swinging doors with louvered openings. Premium models may feature perforated doors with adjustable splash shields to keep spent media inside the blast room while allowing fresh air to be drawn into the enclosure. Ruggedized fabric or rubber roll up doors can be requested at an additional cost. They help reduce the amount of shop space required.

A typical blast room ships with one full-width, full-height door set, and may have one or more separate personnel doors. Some manufacturers offer a curtain wall or curtain door option to reduce cost, but these configurations are not popular with most shop owners because they don’t provide as much containment as other designs.

Get The Right Size

Make sure the blast room is the right size. Many of the considerations we outlined in our powder coating oven size guide will be applicable here, but make sure you give your parts and your operator plenty of room. For example, if the parts you need to blast are very tall, consider adding some additional height to the cabin so you won’t constantly be blasting into your light fixtures or the unprotected ceiling surface. Also, if the part you want to blast takes up the majority of the cabin, give your operator extra width and length to safely work around the part without standing in a stream of blasting media bouncing back towards him. Check out the ovens at https://www.reliantfinishingsystems.com/powder-coating-equipment/powder-coating-ovens/

Part 2: Blast Pot

The blast pot (also referred to as a blasting pot, pressure pot, pressure vessel, media blaster or portable blaster) is the appliance that does the actual blasting. There are a number of blast pots on the market, but all of them work essentially the same way. A blast pot is a pressurized container with a hose and spray nozzle attached. Abrasive media is loaded into the blast pot and sealed air-tight. Once sealed, the media is pressurized using compressed air. A valve at the end of the hose is controlled by the operator. When the valve is opened, compressed air forces the media to travel down the hose and spray out the nozzle.

Four factors affect the price of a blast pot: capacity, portability, construction quality and configuration.

Capacity: Typical blast pots hold 4 to 7 cubic feet of blast media per loading. As an example, the 650 XL model we offer with our Reliant Finishing Systems blast rooms has a 6.5 cubic foot capacity. As a general rule, the smaller the capacity the cheaper the unit, but reduced capacity will increase downtime for reloading.

Portability: The least expensive blast pot models come mounted to a skid or have attachment points so that they can be permanently mounted inside the blast room. Portable units, with wheels mounted to the base of the blast pot, are usually a bit more expensive.

Construction Quality: All blast pots offered by brand-name manufacturers are safe and well made. There are, however, small differences that can drive the price up, but may be well worth the expense. This is particularly true when dealing with premium hose fittings, roomy clean-out openings and more robust sealing systems. Even a simple feature like an adjustable stand versus a fixed one can improve convenience and increase throughput.

Configuration: Almost all common blast pots have one hose and nozzle for use by a single operator, but more expensive multiple operator configurations can be provided by some suppliers.

Other Factors To Consider When Purchasing A Blast Pot

Make sure the blast hose is of the same diameter and length. Find out if each blaster has a safety system to assure that the blasting operation stops instantly if the hose is dropped and the valve at the nozzle released. Determine the orifice size and construction material of each unit’s spray nozzles. Remember, the orifice is sized depending on the media you want to spray and the maximum output of your compressed air system. A larger nozzle takes more air and uses more media, but strips metal at a faster rate.

Part 3: Dust Abatement

When considering options for your blast room, it is very important to remember the difference between dust abatement and media reclamation.

Media reclamation refers to a system that allows you to collect and reuse the blast media (such as steel shot).

Dust abatement, on the other hand, refers to the fans and filters that remove the dust from inside the cabin while the blast room is being used. These fans and filters are separate from the reclaim system and are only used to reduce airborne particulate inside the blasting cabin.

Why is that important? A blast room produces a lot of dust. You are blasting old paint, rust and grime off your parts to get them ready to powder coat or paint. Without proper dust abatement, your operator will be working in a dust cloud that will render him unable to see what he is doing.

The media reclamation system does not move enough air to effectively remove airborne particulate from the enclosure. So, an operator using a typical reclaim unit won’t be able to see what he’s blasting unless the blast room also has a second system designed to filter the air inside the room.

Remember that dust abatement does not remove spent media or heavy debris from the blast room. Dust abatement systems (sometimes called dust collection, dust containment or dust control systems) ONLY affect the airborne dust inside the cabin.

Entry-level blast room models may not come with built-in dust abatement or they may feature a dust abatement system that uses disposable air filters. These simple systems draw fresh air into the room and route exhausted air through a series of filters to ensure that only clean air is returned to the facility. The filters are protected by steel baffles so they are not damaged during blasting, but they must be changed frequently during periods of heavy use. These filtration systems remove enough airborne particles to allow the operator to see what he is doing and to keep the air inside the booth relatively clean.

The most popular dust abatement systems use cartridge type filters. The filters are much longer lasting and can be set up to automatically self-clean using compressed air. These abatement systems usually have a large waste bin located under the filters, and the collected dust and debris falls from the filters into the bin during cleaning, so they may also be considered dust containment systems. The collected dust and debris is usually removed manually by the operator, but upgraded models exist which include a pump that transfers the dust and debris out of the collection area.

More expensive cyclonic dust removal systems are available, but for most buyers the cartridge filtration option offers the best mix of affordability and performance. Both cartridge and cyclonic systems provide excellent dust abatement and allow operators to see clearly inside the blast room, even though some amount of airborne particulate inevitably ends up settling on the floor of the enclosure.

Part 4:  Choosing the Right Media Reclamation System

A powder coating shop can increase throughput, reduce blasting costs and assure code compliance by bringing their blasting operation indoors. They can further improve profitability by using recyclable abrasive media. To make the most of recyclable abrasives, an efficient recovery system is needed.

A media reclaim system usually has a low-volume/high-pressure intake that moves spent media, debris and dust out of the blast room. (As we said before, that does not make it a replacement for a good dust abatement system because the volume of air being exhausted is not enough to clear the air.)

It is not uncommon to see a blast room with dust abatement but no recovery system for spent blast media. Although recovery systems speed throughput even if the blasting media cannot be reused, most shops that use disposal blasting grit don’t use any type of recovery system.

Media Reclamation/Pneumatic Recovery Systems

Blast Room With Pneumatic Recovery System From Reliant Finishing SystemsMost sweep-in media recovery systems, which are often provided in addition to dust abatement equipment, offer an economical alternative to full-area media and waste recovery. A sweep-in system can be installed inside a new or existing blast enclosure. This will increase throughput and allow you to switch to recyclable abrasives. In a high-production environment, the cost savings and increased productivity can pay for the recovery system within months.

Conventional sweep-in media reclamation systems are pneumatic. These recovery systems efficiently remove most low to medium-density blast media, such as sand, glass beads, plastic, nut hulls and aluminum oxide. The recovered media, if reusable, can be recycled. A pick-up bin or trough can be mounted in a shallow pit in the floor for a true sweep-in operation, but is often surface mounted when the owner wants to be able to move the pick-up bin (or when the situation will not allow excavation of the shop floor). Some shops that use non-recyclable blast media still choose to install a pneumatic recovery system in order to increase throughput and prevent operators from spending time shoveling spent media into trash bins to be hauled away. They use the pneumatic system to transport the waste into large trash hoppers that can be emptied less frequently. With many pneumatic systems, debris is sorted from spent media via a classifier that relies on cyclonic airflow–debris is routed into trash hoppers and recovered media is returned to the blast pot’s feed system.

Media Reclamation/Auger (Screw-Type Conveyor) Recovery Systems

Auger systems are designed primarily for use with heavy, durable media like steel shot. These screw conveyor systems can be linked to a pneumatic recovery system when using lighter blasting media. For steel shot, a reclaim module mated to a bucket elevator can continuously process up to almost 200 cubic feet of media per hour. Augers are commonly available in lengths of 8’ to 20’, and can be provided in lengths of 50’ or more by special order. Most augers feature 6” helical flights. It is common for these systems to have integrated metering plates to prevent over-loading. Since they are used most often with steel grit and shot, most screw-type conveyors are mounted in an excavated pit so that the heavy-weight media can be pushed into them using a skid loader or easily shoveled in by hand.

Media Reclamation/Hopper & Bucket Elevator Recovery Systems

A hopper and bucket elevator recovery system serves as something of a hybrid between an auger type system and a pneumatic system. Since the pneumatic systems cannot transport heavy blast media, an elevator is required. The hopper and elevator system requires the operators to move the material into a recovery bin (just like pneumatic sweep-in systems). With diligent operator support, you can process up to about 180 cubic feet per hour of dense media, such as steel grit and shot. Typically, a small reclaim bin or hopper is mounted flush with the shop floor inside the blast enclosure and the operators use shovels or brooms to push spent media into it. When a flush-mounted hopper cannot be used, a smaller stand-alone or wall-mounted bin can be used and loaded by the operators using shovels.

Media Reclamation/Belt Conveyor Recovery Systems

Belt conveyor recovery systems are expensive, but use fairly simple technology to automate the recycling process. A typical complete belt conveyor system includes recovery bins, floor grating, a series of motor-driven belts, a bucket elevator, and an abrasive cleaner (such as an air wash system). When someone talks about a “full floor” or “full area” recovery system, they are usually talking about a belt conveyor system. There are also many versions that have collection built into only part of the blast room’s floor.

Belt conveyor systems include one or more collection bins installed in a recess in the blast room’s floor. Partial-area collection systems can be configured in a single linear run or in “H,” “L” or “U-shaped” patterns as required for the particular application. Reinforced floor grates, mounted flush with the blast room floor, cover the collection bins. Spent blast media falls through the grating and into the hoppers and travels through a metering tube before falling onto one or more conveyor belts below. A separate motor drives each belt, and conveys spent media and debris to a bucket elevator for transfer to the abrasive cleaner.  As with auger or hopper systems, spent blast media is returned to a recovery bin. Specially designed buckets transport the abrasive blast media from the bin to a cleaner, where the abrasive material is separated from dust and debris. Debris falls into a waste container, dust is drawn into a separate dust collector, and reusable abrasive media falls into a hopper used to feed the blast pot.

Part 5: Safety Gear

Don’t skimp on safety. Professional quality safety gear can actually help operators be more productive, so it pays for itself fairly quickly. A good safety package starts at around $1,000. It usually includes protective wear, a helmet and respirator, and a good air filter system. Although it looks cumbersome, once an operator adapts to using this type of gear he is almost always working faster because he doesn’t have as many safety concerns and he can see what he is doing while working near the surface he is cleaning. This is especially true when dealing with detail work that requires a close-up view.

Not only can safety gear increase throughput, it helps reduce liability and prevent injuries to your employees. Safety gear is a win/win for your shop and employees and it’s an option we strongly recommend.

Part 6: Professional Installation

Some very expensive small and mid-size blast rooms arrive at your site ready to install. You connect the blasting and exhaust components, then add power and air. Because these pre-built rooms must ship via truck, these blast rooms’ interior dimensions are limited to heights and widths of less than 8’. Other than these models, there are a few DIY kits on the market, including affordable blast room kits manufactured by Reliant Finishing Systems.

For the vast majority of the blast rooms on the market, installation by factory-authorized technicians is required. In all cases it is recommended! The cost of installation labor is either built into the equipment price or listed as an add-on service. Whether you buy a small blasting room for occasional use or a giant blasting enclosure for non-stop blasting, professional installation helps assure that your equipment will operate safely and effectively.

Part 7: Material Handling

Once you start blasting, you’ll be faced with the need to safely support parts while a powerful stream of abrasive material is directed towards them. If your current racking and handling system has problems transporting parts from your powder coating booth to your oven, it probably won’t be secure enough to keep parts in place while they are being blasted.

You can develop a better way to secure parts through the entire prep and coating process, but many coaters go to a manual or semi-automatic system where parts are dealt with during blasting (and chemical pretreatment if used) and then transferred to a different hanging system for coating and curing.

Any Questions?

No matter what type of blast or pretreatment system you are considering, the experts at Reliant Finishing Systems can answer your questions and provide the equipment you need to get the perfect finish every time. Give us a call today.

Buying New vs Used Powder Coating Equipment

used powder coating equipment

When you purchase used powder coating equipment, there’s no guarantee you’ll get what you need.

For many businesses, investing in capital equipment is the largest purchase decision they are likely to make. It is not surprising that many business owners, coating line managers and purchasing agents look to reduce their businesses’ expenses by purchasing used or salvaged equipment. This can sometimes appear to be a very effective way to save money – however, the reality of new vs used powder coating equipment, the potential problems often far outweigh the anticipated cost savings.

It’s true that buying smaller, less complex tools, such as a saw or welder, from a used equipment dealer or directly from the previous owner may save you money. Unfortunately, that’s rarely the case with more complex machinery. Powder coating booths and ovens are prime examples of equipment that is almost never a good value to buy used, no matter how low the price.

A powder coating system should be matched to your specific requirements, but the likelihood of you finding exactly what you need in a used system is very slim. By the time you have modified, upgraded, refitted and refurbished a used or salvaged coating system, you will have often spent as much – if not far more – than if you had invested in a properly sized new system from the start.

Avoid The Hidden Expenses Of Buying Used Powder Coating Equipment

For this article, we reached out to a few of our clients (some purchased new equipment from Reliant Finishing Systems instead of buying used, and some first bought a used system before investing in a new Reliant system). We asked them to tell us about their experiences while shopping for their coating systems. Our goal was to find out what challenges a used powder coating system can present to a new coating operation. The feedback we received was overwhelming; if you’re considering buying used equipment, don’t do it!

Here’s some of the biggest headaches that buyers encountered:

No Factory Warranty On Used Powder Coating Equipment

Very few used ovens or powder booths have a warranty for their parts. Your oven is the heart of your coating operation, so any downtime can kill you. If the oven goes down, you will be completely unable to cure your parts. Along the same lines, a motor failure or damaged/clogged filters in your booth can leave your coating line at a standstill. Without a warranty on hard-to-source parts like specialized bearings, fans, and burner components, repairs due to mechanical failure are potentially very expensive and time-consuming.

Another issue is that used powder coating equipment has often been modified by previous owners. Figuring out exactly what parts are actually being used can be an added hassle and one you’ll have to navigate by yourself. Contacting the original manufacturer of the equipment will often get you nowhere. These companies are worried about liability, especially if the used system was heavily modified or improperly disassembled / installed. Without any factory technicians there to verify the condition of the equipment, most manufacturers won’t help you if you have a used system. If your equipment has a critical parts failure, you’ll be stuck on your own.

No Factory Support

Hand-in-hand with the lack of warranty, used equipment is often sold without any sort of support from the original manufacturer. In fact, many oven manufacturers from the 1980s and 1990s are out of business. A few from the last ten or so years have also folded, so there is a chance you may buy an appliance that looks good but is totally unsupported. This can be a huge problem down the road if any wear parts are proprietary in nature. It can also be problematic for day-to-day operations, as there are fewer and fewer trained technicians still familiar with the minor problems that may arise with products from suppliers that are no longer in business.

Used Powder Coating Equipment May Not Work Like It Should

When buying used powder coating equipment and basing your decision on price alone, it can be tempting to purchase equipment that is similar to what you need, even though you know it is not an exact match to your requirements. This can be a costly and hazardous mistake.

For example, buying a salvaged gas-fired oven that was used for curing ceramics or heat treating metal may seem like a great idea because the price is $10,000 lower than buying a new batch oven designed specifically for powder coating. In the long run, the oven may not be effective for your powder coating operation. Why? Because buying an oven with a recommended temperature range higher than a powder coating oven may result in over-cured parts and wasted money due to reworks. Trying to run a lower-temperature oven at powder coating temperatures can be extremely dangerous, especially if you are running the oven outside the recommended safety range by bypassing safety devices. In all cases, buying an oven that hasn’t been optimized for powder curing will result in fuel bills that are much higher than they should be.

Buying the wrong oven for the job will cost you money in fuel and can cause powder overbake, damage the parts themselves, or be a fire hazard. There’s also the possibility that your code inspector will simply “red tag” your appliance and you’ll be unable to use it.

Incorrect Power Can Cause Expense & Delays

A low price on used powder coating equipment may not make up for the potential expense of hundreds or thousands of dollars spent for rewiring and replacing controls. Capital finishing equipment is typically designed for each specific customer, and that includes correct wiring for that customer’s location and power source. If you buy used, you may find your equipment wired for single or three phase when you need the opposite. You may also end up with equipment designed for a voltage that is not compatible with your current power source. These differences can lead to significant rewiring and the need for a new or heavily modified control panel. Obviously, this will add to the cost significantly.

We’ve encountered shop owners who bought used or salvaged equipment at auction and the power was designated only as “high voltage” or “3-phase.” They later learned that they had to choose between spending tens of thousands of dollars on a new incoming power supply to their coating equipment or dealing with the cost and delay of reworking the equipment so it was compatible with the power they had.

Safety Issues May Turn Used Powder Coating Equipment Into A Hazardous Money Pit

Older equipment, especially ovens, will often have different and potentially outdated safety features than current models. If those older safety features cause code compliance issues with local inspectors, you will have problems that can take months to resolve. Imagine being shut down for two or three months after you get your equipment assembled because a flame safeguard in your oven’s control panel or a fire detection photo eye in your used high-end booth doesn’t work properly.

Updating the oven or booth to meet code requirements can be costly. Choosing not to update can incur possible fines or your local Authority Having Jurisdiction may simply lock you out of your equipment. If this happens, it will be illegal for you to operate your coating equipment until it has been upgraded to meet certain performance or safety specifications. Even if no inspector is involved, the safety features of used powder coating equipment need to be checked and replaced if they no longer operate properly, as bypassed or outdated safety features can pose a serious safety risk to you and your employees.

Missing Parts Cause Expensive Delays Or Make Used Coating Systems Inoperable

Many used systems have been salvaged. More expensive ones are usually shown under power and then torn down and packaged for shipment. Some used coating systems are missing key components, but it is hard for the buyer to know exactly what has been left out until the equipment is being installed at his facility.

It isn’t uncommon to see used powder coating equipment outlets offering systems made from two (or more) salvaged appliances from totally different coating lines. These products are packaged together in order to make one complete system. Without knowing precisely what is missing and what has been replaced on the system, it is almost impossible to determine if a used powder coating system has all of the capabilities it was designed to offer.

Two of the most expensive items to replace on a powder coating oven, the gas burner and the control panel, are the most likely to be absent, damaged, modified by previous owners, or just plain worn out. Replacing those two items alone can increase the price of an “inexpensive used system” by $10,000 or more before it can be used at a new location.

Salvaged powder spray booths often lack useable filters. A complete filter set for a well-made cartridge filter system can easily cost over $1,000. A set of HEPA filters for a booth with a spray-to-waste filter system can cost almost as much. There’s also the cost of replacing old mismatched bulbs with new ones, replacing broken glass in light fixtures (required by code), and making sure the exhaust system has all of the motor and belt guards in place.

Without the correct replacement parts, a bargain priced (but incomplete) used coating appliance can leave the new owner in a bad situation.

Older Guns & Powder Reclaim Systems May Have Parts You Can’t Replace

Depending on the brand and the specific model, some powder guns that have been discontinued for only a few years may be all but worthless. These guns and their related reclaim/powder transfer systems may no longer have available replacement parts. Once they wear out, the only way to get replacements is to track down other used systems to salvage. What’s worse, if you aren’t dealing with one of the larger powder gun companies (Gema, Nordson and Wagner), used gun systems similar to the one you are buying may not have compatible parts, even though the gun model is identical. This is especially true of guns that are designed to look like brand name guns but have been manufactured in Asia or assembled in hobby shops in the U.S. using foreign parts. These low-end guns are commonly sold via the Internet, and we’ve seen products where key components have been changed multiple times within only a few months without any change to the model designation.

Structural Modifications May Be Required After Reassembly

Ovens expand and contract during operation. This can cause warping of the panels or weakening of structural components. Depending on how often, and in what manner the used oven was operated, the panels may not fit correctly after disassembly. Once relieved of the pressure created by fasteners and adjacent components, panels may deform. Any unusable panels will either have to be purchased from the original equipment manufacturer or provided through a custom fabricator. Additional bolts, self-tapping screws and/or sealant will also have to be used in order to prevent hot air from leaking through improperly fitting wall or roof panels.

On many popular batch ovens, the doors are permanently fixed to a door frame assembly. Often these doors have been custom fitted in the field so that the doors operate properly even if the floor at the installation site is imperfect. During reassembly, it is common for the door components on a used powder coating oven to require modification in order to work with the floor imperfections found at the new installation location. This can be another costly and time-consuming modification that will often require communication with the original manufacturer.

Interior Rust May Be Undetectable Until It Is Too Late

If an oven has been installed or stored in a humid environment, the insulation can trap moisture against the interior of the wall panels. Although their construction is designed to deter rust, the panels of a used oven can be rusting from the inside out and the rusted panels will have to be repaired or replaced. Without tearing the panels apart, it is impossible to know if rust is going to be an issue. The oven may look fine, but a rust problem may not be apparent until it is too late to avoid costly panel repairs or outright replacement. The more an oven has been moved or disassembled/reassembled, the more likely it is that rust may be a concern.

Insulation Doesn’t Always Travel or Age Well

Most ovens feature 4” or more of mineral wool insulation. Reliant Finishing Systems is somewhat unique because our ovens feature 6” panels that can be completely broken down. This allows the buyer to be confident that each and every panel has been properly insulated. What we’ve learned from working with dozens of tons of mineral wool every year is that it often settles inside an oven’s panels—especially if exposed to a moist climate. We’ve taken apart a handful of panels from used ovens that were installed when new, then disassembled and sold a few years later as “like new.” The rigors of being shipped thousands of miles, then having the panels slammed together during assembly and snatched apart during tear-down caused the mineral wool inside to break down slightly. After a few years of use, the insulation began to settle. As a result, the “good as new” used oven’s wall panels had no insulation at the top of the panel. Another thing we noted was that after being subjected to high temperatures for a few years, the insulation became somewhat brittle. Instead of a stiff board of insulation inside, the panels had insulation that no longer evenly covered the entirety of the panel. This lack of fresh mineral wool throughout the entire oven construction leads to heat loss and safety issues. Even with our own ovens, a certain amount of insulation will need to be replaced if a Reliant oven is going to be moved and reassembled.

Installation Labor Is The Biggest Gamble

When you buy new equipment, the manufacturer or the equipment dealer typically offers installation services. These services are provided at a set price and include calibration of the equipment. Factory-installed equipment should look good, perform well, and be safe and reliable. When you buy used powder coating equipment, one of the biggest hidden costs is the likelihood of the installation bill being significantly higher than originally expected.

When buying equipment that is “as is, where is” at a low price, it is easy to forget about the cost of having the equipment torn down and packaged for transport. As an example, let’s consider a large batch oven and powder spray booth package that includes some structural steel supports. Let’s say that if the equipment is bought used it will save you $25,000 over buying new. Let’s estimate that the cost for having new equipment installed is going to be $15,000. It is reasonable to expect to pay more to have the used equipment built because technicians charge more to offset the delays that they anticipate with used equipment, so $20,000 is a solid estimate. Then you have to pay to have the equipment removed from the original site, which might cost $7,500, plus you’ll spend maybe another $2,500 to have the equipment broken down and containerized for shipment. So, you’ve saved $25,000 on equipment but paid out an extra $15,000 in labor compared to buying a new system. So, you’re still $10,000 ahead—until a problem crops up.

What if some panels get damaged because they were screwed together instead of being held together by friction the way they should be? Perhaps the heat unit breaks into two pieces because the original installers failed to assemble it correctly. There’s no way an independent installation crew is going to absorb these costs because they didn’t build the equipment the first time. The original manufacturer is unlikely to offer to provide labor because they don’t want to inherit a bunch of problems or assume any liability from the previous owner.

When working with factory-authorized crews that are assembling new equipment, installation goof ups should get taken care of free of charge. When dealing with used equipment, the meter never stops running. You have to deal with the unexpected costs. It is easy to end up spending so much on labor and repairs that the deal you got on your used powder coating equipment is no longer a bargain.

These are just a few of a multitude of issues to be aware of when considering buying used powder coating equipment instead of buying a new powder coating system. Many of the problem issues can be monetarily quantified, so you can decide if the risk is worth it, but the peace of mind that comes from buying a quality powder coating system with a warranty, professional installation and years of factory support is hard to measure.

Three Common Powder Spray Booth Misconceptions

Misconception 1: If you buy a high-quality powder spray booth, you won’t need to change the filters often.

Powder Spray Booth Bag Filters Comparison


Every powder spray booth needs to have the inexpensive filters changed regularly. Not changing the filters can significantly reduce performance and damage the equipment.

No matter how well designed a powder coating booth is, the filter media that it uses can make or break its performance. One of the biggest misconceptions around is that a good booth doesn’t need expensive filters or doesn’t use cheap ones up quickly. All o powder spray booths either have very expensive cartridge or cyclonic exhaust filtration systems or use disposable filters that must frequently be replaced. A booth that is cheap on filters isn’t doing its job!

Powder Spray Booth Bag Filter Saturated With Powder

One of the main reasons that shops buy booths is because they want to turn out better quality powder coated finishes. They need to be able to get a clean finish every time. They also want the booth they buy to be long lasting and dependable. By using cheap filters or running equipment with dirty filters (or even worse, without filters), the owner saves a little in filter expense but costs the shop a great deal over the long run. A booth that uses disposable filters but doesn’t get frequent filter changes won’t have enough airflow to get top-notch results. Trying to stretch things out by postponing filter changes only makes the equipment’s performance decline further.

Powder Spray Booth Blanket Filter Saturated With Powder

Many powder spray booths are equipped without doors. If you have a relatively clean shop, filtered doors or wall or roof-mounted intake filters aren’t a necessity when working with powder, but compromising on exhaust filtration is a mistake. Using a cheap panel or blanket filter instead of a cartridge filter system or multi-stage disposable filter system may reduce a shop’s filter costs, but it means that debris gets blown back out into the shop atmosphere during use—which creates an increase in airborne contaminants. More contamination translates to more reworks. The reason you don’t have to change cheap filters as often as premium filters is because they are not filtering out as much trash and overspray. It also usually means that the exhaust fan is taking a beating from airborne dirt and powder overspray. Over time, powder builds up on the exhaust fan, reducing the amount of air it can move and adding stress to the motor and drive system.

By using inexpensive filters or using filters beyond the point that they should be changed, operators increase their long-term costs for a variety of reasons: clogged filters reduce the effectiveness of the exhaust and make it harder for the coater to do a good job, poor filter maintenance results in more incidents of booth down-time, increased dirt in the finishes means more reworks, inconsistent performance keeps the coater from mastering booth and gun operation, etc.

Powder spray booths from Reliant Finishing Systems all use premium filters and we recommend regular filter changes.

Misconception 2: All powder spray booths that have the same airflow rating (such as 12,000 CFM) work about the same.

When purchasing a powder spray booth, know what kind of fan(s) the exhaust system uses so you can anticipate how the booth will perform as the filters begin to fill with powder.

Powder spray booths all have exhaust fan systems that are rated based on how much air they move. This is measured in cubic feet per minute (CFM) of airflow. Some companies improve their ratings by using theoretical values. Basically, they use a performance rating that can only be reached if the exhaust has been detached from the booth and filters. To understand how robust a booth’s exhaust really is, it’s critical to find the static pressure at which the booth’s airflow is being measured. This is measured in inches of water column (shown by using the inch symbol with or without the initials w.c. or s.p.). In order to compensate for the restrictions of filters, ductwork, etc., on the exhaust of a powder spray booth, the rating should be at 1” or more of static pressure in order to be meaningful. Powder spray booths from Reliant Finishing Systems are typically rated at 1.25” to 5.75” of static pressure, depending upon the type of booth and exhaust.

There are two main types of fans that are used in powder spray booths and ovens: “propeller” style and “wheel” style. Propeller style fans include tubeaxial fans, some so-called turbo fans and others. Wheel fans include single and double inlet forward-curving fans, barrel fans, backwards-inclined fans, “squirrel cage” fans, and others.

Propeller style fans work well at lower static pressures. They’re usually not as efficient under load and they tend to be noisier, so they are less common on automated or constant-process lines where the exhaust must overcome the load of a restrictive, low maintenance filter system. Since powder spray booths use filters that increase the load the fans must overcome, propeller style fans can run out of power unless they are configured with adequate motors mated to ideally sized blades. Contaminated filters can reduce a low quality or underpowered 12,000 CFM propeller fan to less than 8,000 CFM with no real warning except for poor air movement. When considering a product that uses a tubeaxial fan, make sure that the advertised airflow is at a reasonable static pressure.

Powder Spray Booth With Tubeaxial Fan

A premium quality tubeaxial fan, mated to a reliable motor of adequate horsepower, can provide good exhaust performance at an economical price for a spray-to-waste type booth.

Some units use a backwards-inclined wheel fan that creates a vacuum on one side as it spins. These fans perform well under high static pressure, but their maximum airflow is quite limited—often 10,000-12,000 CFM or less on a large walk-in sized powder spray booth. They are typically well made and more expensive than tubeaxial fans, but suffer from a lack of efficiency because their maximum output requires a much larger motor than many other fans. They overcome high static pressure loads, but this may be unnecessary if the booth is maintained properly and is being used for a spray-to-waste process.

If you are thinking about reclaim for your powder operation, remember: Almost all systems where the powder media will be reused feature reinforced wheel type fans. These exhaust systems are typically more expensive, but are necessary when working with cartridge type filtration modules.

Squirrel cage fans provide premium performance under moderate load. They are smaller, quieter, and more efficient than many other designs. The dual inlet/dual outlet forward curving fans used in some booths achieve a balance between maximum airflow and the amount of load they can overcome. Because the blades are smaller, better formed and more rigid in these fans, they distort less when they meet resistance. These types of fans are not as widely used because they can be costly and their advantages are greatest for buyers of booths built for very specific powder coating applications. A small dual-inlet squirrel cage fan can move more air than a larger backwards-inclined wheel type fan and can outperform much larger propeller style fans under moderate load.

Misconception 3: A powder spray booth needs to have lights in the walls and should be very bright inside.

Powder Spray Booth With Lights

OSHA and other independent organizations have determined that a painting enclosure needs about 100 to 150 foot-candles of light at the object being painted to reach an ideal painting atmosphere—from safety, ease-of-use and production efficiency standpoints. Too much light or poor light quality can detract from this environment. The bulbs used for illumination should have very accurate color rendering to get the best results. Many bulb providers offer high-intensity bulbs that have a rating of over 90 CRI and a color temperature of over 5000° Kelvin. These specially formulated bulbs cost more, but they provide broad spectrum illumination much like natural sunlight. The concept is to match a cloudy summer day where the light seems a little hazy and diffused. Blasting the parts with lights–the “more light is better light” approach–is scientifically unsound. The human eye best discriminates color when the colored surface is compared to a background that is about 18% gray, not glaring white.

Well-designed booths help coaters see problems before the parts are moved to the oven to be cured. Coaters also get better color matches. A white powder spray booth interior can be helpful, but a conventional galvanized booth can work fine–if you keep it clean! All of Reliant Finishing Systems’ flat roof booths are designed so that a large portion of the light bounces from our ceiling-mounted fixtures onto the booth walls and then onto the surface of the object being painted. The light is somewhat indirect and much like a cloudy summer day. At the level of most surfaces being painted, the booth walls are not glaringly bright because the light from the ceiling fixtures has dissipated. This is the ideal painting atmosphere for accurate color matching, touch-ups and detail work. Our lighting method creates lighting that is more even in tone. A typical Reliant powder spray booth provides about 150 foot-candles at the center of the booth.

Wall-mounted lights make detail work harder and hinder color matching. The painter has to look directly into these lights when he is painting across from them. As a result, backlighting causes the painter to perceive that the surface being painted is darker than it really is. This can cause the painter to miss critical details. Also, he casts a shadow on the parts he is painting whenever he stands in front of a wall-mounted light. As a result, he ends up trying to work on parts that are poorly lit due to his own shadow. Even worse, when overspray gets on the wall-mounted lights, they can tint the perceived color of the object being painted or obscure critical details. A little bit of blue powder faintly covering part of the lights would give a section of a yellow part a faint green cast, making it harder to judge powder coverage. Wall-mounted lights require extra maintenance to prevent botched jobs.

Hip-mounted lights can lead to finish quality problems. Booths for wet paint applications that have “hip” style roofs are popular in the collision repair industry because they are cheaper to buy and easy to service. Some of these booths have been adapted for use in the powder coating market, though they are not ideal. This design typically has lights mounted in the hip panels because the ceiling is so small that there isn’t enough room for all of the lights. Some inexpensive hip roof booths also have very short side walls. As a result, a portion of the light coming from the fixture behind the painter is blocked by his head when he works close to the center of the booth. This causes the painter to work in his own shadow. As explained previously, this is not a situation where your painter can excel.

Some parts are harder to light than others. Even with well-designed indirect lighting, if you have a ceiling-to-ground object that fills the powder spray booth, or one with curved surfaces (like a fuel tank or an antenna dish), the bottom part of the object may be somewhat shadowed because it is curved so heavily. The correct solution is not to add lights, but to adjust throughput expectations and allow the coater enough time to do a good job. In exceptional cases, a shop may choose to add a better reflector, such as white floor tiles or stain-proof white floor paint when practical.

By doing research before you acquire a new powder spray booth for your operation, you can help prevent unpleasant surprises and disappointing equipment performance.

Need advice about your powder spray booth? Contact Reliant Finishing Systems at (888) 770-0021 and ask for a powder coating systems specialist.