How to Build a Powder Coating Oven

Powder coating requires either an oven or infrared heating in order to cure the powder.   A household oven or even a toaster oven are great for smaller parts, but you will always be limited by the oven size.  If you are interested in a smaller oven, check out the original oven article: Powder Coating Ovens. If you want to start powder coating large parts, you will either need to spend a lot of money or make your own.  In this article, I will be focusing on how to build your own powder coating oven. It may seem intimidating if you have never attempted this kind of project, but with the information available on the internet, you can easily tackle this job, save money and end up with a large powder coating oven.  No welding is required to build the powder coating oven featured in this article.  This is part one of a two-part powder coating oven build.  See How to Build a Powder Coating Oven Part II for the remaining steps.

You can build your powder coating oven to the size you need, and you can also build in some features to make your powder coating more efficient.  This article is a guide to give you an idea of what all is involved and the basic oven construction principles.  A unique thing about this oven is that absolutely nothing protrudes into the oven space.  The entire interior space of the oven is usable.  All heating elements, lights, fans, etc. are recessed into the walls.  Building the oven this way allows you to build a powder coating rack that tightly fits into the oven with no wasted space.  You would do all of your powder coating on the rack, then roll the rack into the oven for curing.  This however, does add some complexity and increases the cost of materials needed to build the oven.  You can choose to build your oven like this for maximum space savings or you can go the traditional route.  The great thing about building your own oven is that it is completely up to you.  This particular oven costs around $1,400 to build.  Some money can be saved by not recessing everything as that requires more building materials.  But plan to spend at least $1,000 for an oven build of this size.

 Features of this Powder Coating Oven

• 3.4 ft Wide x 3.4 ft Deep x 6.5 ft Tall 
• Rivet construction, no welding required
• 20-gauge sheet metal with 16-gauge sheet metal on the floor
• 4 recessed 2000 Watt  heating elements (240 Volt service)
• Recessed lighting
• Recessed convection fan and ducting
• PID controller
• Window in door 

 

Quick Rundown of Powder Coating Oven Construction and Materials.

The basic construction of this and most powder coating ovens is a steel stud and steel track frame which is riveted together.  Both sides of the frame will be skinned with sheet metal with insulation in between.  This oven uses 20-gauge sheet metal everywhere except for the floor which is 16-gauge sheet metal.  The reason for the thicker gauge metal on the floor is to allow it to support the weight of a powder coating rack.  All sheet metal, studs, and track can be purchased locally from Home Depot, Lowe's, or a local metal supply company.  You can buy it online as well, but shipping costs will likely cancel out any cost savings.   It is best to shop around, call some metal supply places in your area and get some quotes.  Inside of the oven is where you will put the heating elements, which will be wired to a control box on the outside of the oven.

Let's Get Started - Framing Materials & Tools

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We will start with the framing.  The framing for this oven will all be made with galvanized steel studs and track. Steel track is very similar to steel studs except that they do not have a lip on the inside of the stud.  This allows the steel studs to fit into the track. These are the same studs used to frame homes.  They are available at both Home Depot and Lowe's for about $7.00 each.  They are 3 5/8" wide x 1 5/8" thick and are available in 10' lengths or 8' lengths.  It is best to buy a bunch of these to begin with.  You don't have to get to scientific with it figuring out exactly how many you will need, you can purchase more as you go along.    Working with these is pretty easy as they are quite thin (25-gauge).  They are easy to drill and they can be cut with tin snips or a chop saw.  Since you will be cutting a lot of studs, I recommend a at least a good set of snips like these: Wiss Tin Snips. 

The framing will all be held together with rivets  Rivets are really easy to use, and they are cheap. You first drill a hole, then with a rivet gun, you place a rivet into the hole, squeeze the trigger and you are done.  You are probably familiar with a hand rivet gun, but I strongly recommend a pneumatic rivet gun if you have an air compressor (you have read my article about How to Buy an Air Compressor right?).  A pneumatic rivet gun will save you tons of time and you you'll still have use of your hands at the end of the day.  Again, I recommend a decent pneumatic rivet gun, this Astro Pneumatic Air Riveter offers a good price/performance ratio. It is by no means an industrial tool, but you will pay several hundred dollars for a high end pneumatic rivet gun. Another great option, especially if you have already invested in some Milwaukee M12 cordless tools and batteries, is the Milwaukee M12 Cordless Electric Rivet Gun. You will need lots of rivets to go with whatever rivet gun you decide to use.  The most important thing about rivets is to make sure they are the same type of metal as what you are working with to avoid galvanic corrosion.  Since this is a steel oven build, you will need steel rivets.  Also important with rivets is to drill the appropriately sized hole.  A pack of 1000 3/16" diameter x 1/8" grip steel pop rivets should get you through the oven build with a few left over.  These will allow you to rivet stacks of metal with a maximum thickness of 0.125" and a minimum thickness of 0.020".  Make sure to adjust accordingly if you are using thinner or heavier gauge steel studs and sheet metal. The 3/16" rivets mentioned require a #11 Drill bit for best fit.

Now that you have your rivets, rivet gun, and studs, you can start to build the floor frame.  Make sure you cut and measure the floor to exactly the size you want your oven to be.  Your walls will sit on top of the floor.  When making the square section of the floor, you will overlap the studs so that they sit inside of each other on the corners.  Once you have the studs in place, you can keep them there with a locking c-clamp. You will then rivet where they overlap on top and bottom (see the red dots in the pictures below for rivet locations).  Start with one rivet per corner so that the studs are able to pivot.  Use a speed square to square up each corner (ensuring all corners are exactly 90° before you add an additional rivet to each corner.

Once all four sides of the floor are cut to length, and riveted in place, add additional studs to further brace the floor. Not only does the floor support the weight of all of the oven walls and components, it also should be strong enough to support powder coating racks and even the weight of a person, if you wish to stand in the oven to do maintenance or cleaning. With this in mind, make sure to choose thick enough sheet metal that the floor does not bow in and support it with enough bracing so that it remains sturdy. 

Floor-less Powder Coating Oven? 

An important thing to consider when you are planning your powder coating oven build, is whether you actually want a floor frame or not. The advantage of not having a floor frame is that it allows you to roll a rack of powder coated parts into the oven easily. While this is possible with a floor frame, it requires a two-piece sliding rack. The oven featured in this article can actually be built nearly identical without a floor frame, and instead, using a piece of sheet metal as the floor. You can see in the picture below how a rack would roll into a floor-less powder coating oven much easier.

The same stud, track, and rivet construction is continued for the walls, the picture below is the back wall.  The side walls are made the same way, just make sure you measure and account for the thickness of the back wall.

You will then place the walls on top of the floor, one at a time, and rivet them to the floor:

Once you have the back wall in place, and have constructed the side walls, you will put them in place and rivet them to the floor and to the back wall.

Then assemble the ceiling the same way you assembled the floor:

This is the point of the build where the recessed heating elements come into play.  The heating elements have their own boxed-in sections in the walls, but every square inch of the powder coating oven must be insulated.  The hollow area between the studs is where the insulation would usually be placed, however since the heating elements will be taking up that hollow space in these boxed-in sections, another boxed-in section of insulation must be added to the outside of the oven where the heating elements are recessed.  If you do not plan on recessing heating elements and other items in the oven walls, then you will exclude these boxed-in sections.

Here you can see the boxed in sections on the bottom for the heating elements, along with additional support studs in the walls:

 

Skinning the Inside with Sheet Metal

 

Once the structure is framed up, you then will begin skinning it will sheet metal.  Sheet metal can be purchased at your local Home Depot or Lowe's but if you go through a metal supply company, most of them have will cut the sheet metal to your specifications.  You will need long straight cuts here and companies that deal primarily with sheet metal will have large brakes that can cleanly makes these cuts for you. I recommend galvanized steel sheet metal which will help keep your oven rust free.  This particular oven uses 20-gauge steel everywhere except the floor which is 16-gauge.  When choosing the thickness, you will want to stay in the 16-gauge to 26-gauge range.  Each has its benefits and drawbacks.  Using a thinner gauge is cheaper and will allow the oven to heat up faster.  Thicker gauge is more expensive, but sturdier and will retain the heat better once the oven it is heated up.  This saves on heating costs. The sheet metal used to skin the oven is the primary reason why I cannot give you an exact cost of the oven build.  Depending on your location, the sheet metal price can vary drastically. Its a good idea to google the local sheet metal suppliers in your area and call/email them for a quote. If you can, contact several so you can make sure you are getting a good price.

The first layer of 16-gauge is laid down on the inside of the floor and riveted into place, also additional stud supports are added to the bottom.  Do not skimp on the rivets here, the sheet metal ties all of the framing together and keeps the frame from flexing or sagging.

During this part of the build, you will notice that the sheet metal does not sit perfectly flush against the frame due to the small protrusion of the rivet heads (~1/16"). It is a small gap, and usually not a big deal because the sheet metal is thin enough to conform around the rivets. However, if you want to ensure a perfectly air-tight seal between the sheet metal and the frame, you can use high-temperature sealant between the two, before riveting the sheet metal into place. However, this is a step you must contemplate somewhat. If you need to disassemble the oven for any reason at a later date, the sealant will add considerable time to the process.

The entire inside of the oven is now skinned:

After everything is skinned, the four cutouts for the heating elements are made using a Dremel with a cutting disc.  A pneumatic cut-off tool or cordless electric cut off tool would also work here, whatever you have available to you to cut sheet metal.  Make sure to mark all your cuts accurately with a straight-edge and a square. With enough planning, you can have these cuts included when you purchase your sheet metal.

CONVECTION BLOWER & DUCTING

 

This oven will have a convection system to keep the temperature consistent throughout the entire oven space. When powder coating, consistent and reliable oven temperatures are very important so this is a highly recommended step. The oven circulation is done by adding a high-temp blower to the top that has an intake for the rising hot oven air, which then blows it back down to the bottom of the oven using ducts. This helps equalize temperatures throughout the entire oven.  Here you can see the duct work inside the wall of the oven that brings air from the top to the bottom.  These slim rectangular types of ducts are called stack ducts.  This oven uses 10" wide x 3.25" deep stack ducts for vertical ducting.

This is where the air will exit the duct into the bottom of the oven:

This is the Dayton 310cfm High-Temp Blower that will be used on top of the oven to circulate the air:

Here you can see how the ducting was wrapped around from the side wall to the top of the oven to the fan, and you can see the stack duct elbow partially visible on the top. The same metal studs used to build the oven frame were used to finish the ducting to the blower.

High Temp Sealant was used on the duct work to prevent the forced air from leaking into the oven frame.  This sealant is rated for 600°F (315°C).  The top sheet metal duct piece was riveted into place after the sealant was applied

Here is a picture of the interior top-side of the oven where the inlet for the blower is:

That completes the convection system of the oven.  As you can see, the air is pulled up through the top of the oven and is ducted back down the side wall and into the bottom of the oven using rectangular steel stack ducts, which will equalize the temperature throughout the oven.  This is very important when powder coating as a large oven like this with no circulating air can have temperature fluctuations of up to  50°F from the top to the bottom. 

Lighting

 

This oven build has three recessed lights in the ceiling.  By recessing them, they will never interfere with the powder coated items inside of the oven. Recessing them does take some extra steps and a some extra parts as you can see below.  If you choose not to recess them, all you would need is the ceramic light fixture and appliance bulbs. 
Here is a single finished light assembly before being installed on the top of the oven:

Here are the parts needed to make each light assembly:

Porcelain Lamp-holder (1 per light assembly)

40-watt Appliance Bulbs (1 per light assembly)

6-inch Duct Cap without crimp (2 per light assembly)

6-Inch Duct Flex Connector (1 per light assembly)

 To construct the light assemblies:

• If using the porcelain light fixture linked above, drill a ~2 1/8" hole into the center of one 6" duct cap using a hole saw. This hole gives you access to the wiring terminals on the back of the light fixture. These are thin duct material so it does not matter too much, but when using a hole-saw for metal, you can get the most life out of it by using a cutting fluid and running running the drill with low speeds (400-600 RPM)  

•  On this same cap, drill two screw mounting holes on either side of the previous hole (3 1/4" apart). Use porcelain fixture as a guide to mark the duct cap. A 1/4" or #8 drill bit will be sufficient for these holes.

• Mount porcelain light fixture to 6" duct cap using provided hardware. 

• On the other non-drilled 6" duct cap, drill a hole to allow the light to pass through. The duct cap featured was drilled with a 4" hole saw. 

• Assemble the two duct caps on either side of the 6" duct connector.

• Then frame the assembly you have made with the same steel studs that have been used throughout the oven build.

The bulbs and lamp-holder are completely capable of withstanding the 450°F temps that the oven will be operating at. Here is an exploded view model of the light assembly to help explain this more clearly:

Here is a picture of the backside of the completed assembly. 

Here are the three light assemblies riveted into place.  Before placing them, you will need to cutout holes for the duct caps in the ceiling sheet metal.

You can see the duct caps with holes cut in them placed through the sheet metal onto the light assemblies.  This gives a nice finished look.  The ceiling is completed now with the three recessed lights and blower fan.

Insulation

 

Every wall of the oven needs to be insulated. The insulation keeps the inside of the oven hot, and the outside of the oven cool. The point of insulation is to slow the rate of heat transfer from the inside of the oven to the outside of the oven. The rate of heat transfer will depend on the temperature differential between the inside and outside of the oven, insulation material, and thickness of insulation. Fortunately, most insulation materials are rated R-value which accounts for thickness, so that they are directly comparable. The higher the R-value, the slower the heat transfer rate, and therefore, the better the insulation. The thickness of insulation you choose will depend on how thick your oven walls are. The insulation should not be compressed within the oven walls because this reduces its insulation properties. The most common choices of insulation for a powder coating oven are mineral wool or fiberglass.

Mineral wool insulation, also referred to by the brand name Rockwool, has a higher temperature rating than fiberglass (~2000°F vs ~1000°F), is more durable, easier to work with, and usually comes at a higher price. The R-value for 3.5" mineral wool insulation is R15, while the R-value for 3.5" fiberglass ranges from R11 to R15. As you can see, their insulating properties are very comparable. The decision to choose mineral wool over fiberglass depends on a couple of factors. It holds its shape much better so cutting it and installing it is generally a cleaner and neater process than fiberglass. While fiberglass needs to be compressed to cut with a razor blade, mineral wool can be cut more like a loaf of bread with a mineral wool knife. Mineral wool is considered to be more durable and longer-lasting than fiberglass. Also due to its higher temperature rating, its considered to be safer in the case of an oven fire. Mineral wool insulation can be seen in the picture below, but it was not used in this oven build due to costs.

This oven build uses unfaced R13 fiberglass insulation throughout. The total area of the insulation for all the panels came out to roughly 18,204 square inches (126.4 square feet). This type of insulation is available online or at your local hardware store, and usually they sell it in bulk. You will need to put insulation in between every stud and cut the insulation to fit in any odd-sized spaces. The easiest way to cut insulation is with a sharp utility knife and a long straight edge. When working with insulation, you will want to wear full safety gear including gloves, safety goggles, dust mask or respirator, long-sleeve shirt, pants, and close-toed shoes. It is very itchy stuff and even if you are wearing all of that, you will undoubtedly still be itchy afterwards.

As you can see in the above pictures, the cutouts for the recessed heating elements are not insulated.  These will be the hottest parts of the oven, so of course, they will need to be insulated.  This is where the oven expands outwards.  With the use of individual insulation panels on the outside of the oven, everything is able to be recessed, yet still insulated.  The areas of the oven that will need these insulated panels are the 4 heating elements, the duct-work on the back on the oven, and the entire topside of the oven. All the insulated panels were framed using steel studs and rivets.  However, before these are installed, you will need to install the heating elements and skin the outside of the oven with sheet metal.

 

Heating Elements

 

This oven uses four 2000-watt heating elements for a total of 8000 Watts.  There are a variety of oven heating elements available.  Standard oven heating elements can range anywhere from 2000 Watts to 3600 Watts.

To determine what wattage you need for your specific powder coating oven size, a general rule is that you should have 100 to 150 Watts worth of heating element for every cubic foot of interior oven space.  150 Watts per cubic foot is ideal.  The interior space of this oven is ~75 cubic feet so with 8000 total Watts, that works out to about 106.5 watts per cubic feet. If you live in a colder climate, you should aim closer to 150 Watts per cubic foot.

You can also use BTU calculator for a ballpark estimate but it can be a little off.  To use the calculator, you enter in the interior dimensions of your oven in inches, the average ambient temperature in your area, your desired temperature in °F, and your predicted total heating element wattage. It will then tell you how long it will take for the oven to reach the desired temp based on your criteria. Just keep in mind that 100-150 Watts per cubic feet is ideal.

Below, you can see the four heating elements installed in the oven.

The rest of this oven build is located here: How to Build a Powder Coating Oven Part II.  If you have any questions or comments, please leave them in the comments section below.