How to Build a Powder Coating Oven



     When you are powder coating, you will need an oven to cure the finish.  You only have so many pre-made oven options at your disposal and they all limit you to smaller parts.  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 some 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 worked with metal but with the information available on the internet, you can easily tackle this job, save money and have a huge powder coating oven.  No welding was required to build the following powder coating oven.




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 basic oven construction principles.  The oven featured build featured below was built by KNJ Custom Coating who has agreed to have it featured in this article.  Huge thanks goes out to KNJ Custom Coating, if it were not for them, this article would not be possible.  Head on over to their website to check them out:  KNJcustomcoating.com.  KNJ has built a very nice powder coating oven that measures 3.4' wide x 3.4' deep x 6.5' tall.  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, ect. 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 cost of materials to the oven build.  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 cost around $1,400 to build.  Some money can be saved by not recessing everything as that takes more materials.  But plan to spend at least $1,000 for an oven build of this size.


 Features of this Powder Coating Oven

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

Quick Rundown of Powder Coating Oven Construction and Materials.


The basic construction this and most powder coating ovens is a steel stud frame which is riveted together.  Both sides of the frame will be skinned with sheet metal.  This oven uses 20 gauge sheet metal everywhere except for the floor which is 16 gauge sheet metal.  Having thicker sheet metal on the floor makes it a little sturdier so you can stand on it.  All sheet metal and studs can be purchased locally from your Home Depot, Lowes, 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.   In between the 2 layers of sheet metal will be your insulation. 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

We will be starting with the framing.  The framing will all be made with galvanized steel studs.  These are the same studs used to build houses.  They are available at both Home Depot and Lowes for about $5 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 pretty thin (25 gauge).  They are easy to drill and they can be cut with tin snips.  Since you will be cutting a lot of studs, I recommend a at least a decent pair of snips like these: Bostich Straight Aviation Snips.




The framing will all be held together with rivets... LOTS of 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 will do the job just fine.  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.  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 rivets should get you through the oven build with a couple left over.



Now that you have your rivets, 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.  You're 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 how 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 1 rivet per corner so that the studs are able to pivot.  Use a speed square to square up all of your corners before riveting into place.  After you have all 4 sides secured like below, you can then go back and add more rivets to each corner.


Once you have the the 4 sides of the floor done, you will add more studs for support using the same procedure as above.




The same procedure is used for the walls, below is the back wall.  The side walls are made the same way, just make sure you measure and account for the size 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:


At this point is 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 place between the studs is where the insulation would normally go, 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, then you will exclude these boxed in sections and just add in more support studs in the walls above before riveting them to the floor.

Here you can see the boxed in sections on the bottom for the heating elements along with more 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 Lowes 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 metal companies have gigantic brakes that will make short work of it. I recommend galvanized steel sheet metal which will help keep your oven rust free.  As far as what thickness to buy, this particular oven uses 20 gauge 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 hold the heat better once the oven it is heated up, which will help the oven stay at the correct temp in colder climates.

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.



The entire inside of the oven is now skinned:



After everything is skinned, the 4 cutouts for the heating elements are made using a Dremel.  A pneumatic cut-off tool would also work here.  Make sure to mark all of your cuts accurately with a straight-edge and a sharpie. 




CONVECTION BLOWER & DUCTING

This oven will have a convection fan on the top that will circulate the air from the top of the oven to the bottom.  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.  




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, from the angled piece of duct work on the top, the same metal studs used to build the oven frame were used to finish the ducting to the blower.








Then High Temp Sealant was used on the duct work for an air-tight seal.  This sealant is rated for 650 degrees F.  Then the top sheet metal duct piece was riveted into place.





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


And that completes the convection part 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 through the use of rectangular metal ducting.  This will equalize the temperature throughout the oven.  This is very important when powder coating, an oven with no circulating air will have hot spots 50 degrees higher than another part of the oven.


Lighting

This particular oven build has 3 recessed lights in the ceiling.  By recessing them, they will never get in the way of powder coated items inside of the oven.  Recessing them does take some extra steps and parts as you can see below.  If you choose not to recess them, all you would need is the light fixture and the bulbs. 
This will be the finished product before being installed on the top of the oven, there are 3 of these in this build:



These are the parts needed to make each light assembly:

Porcelain Lampholder (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 make the light assembly, you will install the porcelain lampholder onto the inside of the 6 inch duct cap.  Drill  holes for the lampholder mounting hardware and drill a center hole to have access to the wiring terminals.  You then place the end cap with lamp holder onto the splined Duct Flex connector.  Then you frame the assembly you just made with the steel studs that have been used throughout the oven build.  The bulbs and lampholder are completely capable of withstanding the 450 degree temps your oven will be operating at.  Here is a picture of the backside of the completed assembly. 


Here are the the 3 lamp 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 3 recessed lights and blower fan.







Insulation

Every wall of the oven needs to be insulated.  The insulation is responsible for containing the heat inside of the oven.  Also, without the insulation, the exterior walls of the oven would get extremely hot.  The common choices of insulation for a powder coating oven are mineral wool or fiberglass.  Mineral wool insulation has a higher temperature rating, however it comes at a higher price.  If you plan on curing ceramic coating in your oven, I would choose mineral wool because of the higher temperatures that ceramic coatings need to cure at.  If you only plan on doing powder coating, you can use fiberglass insulation and save some money.

This oven build uses unfaced R13 fiberglass insulation throughout.  2 Batts of insulation were used with some left over.  Insulation like this is available online or locally at Home Depot or Lowes.  You will need to put insulation in between every stud.  You will need to cut the insulationt to fit in any odd-sized spaces.  The easiest way to cut insulation is with a sharp utility knife using a 2x4 as a straight edge.  When working with insulation, you will want to be wearing full safety gear including gloves, safety goggles, dust mask, longsleeve 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 cutout's 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, every thing 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 ductwork on the back on the oven, and basically the entire topside of the oven. All of 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 4 2000 watt heating elements for a total of 8000 watts.  You can purchase heating elements online or you can salvage them from old household ovens, however they are are relatively cheap brand new.  To determine how many heating elements what wattage you need for your specific powder coating oven, you can look at this BTU calculator


. To use the calculator, you simply enter in the interior dimensions of your oven, and the increase of temperature over ambient. If you live in 0 degree weather, and you need your oven to reach 500 Degrees F, you would enter 500 Degrees. If you live in sunny 80 degree weather, you would enter in 420 Degrees F. It will then specify the wattage that you will need. It is not an extremely accurate method, but it will give you a ballpark figure. This particular oven needs about 4000 watts, however you can see the builder went a little overkill and decided to use 8000 watts which is still fine. The heating elements will be configured and controlled with a PID so it is okay to have more than you need. Below, you can see all 4 heating elements installed in the oven.


The rest of this oven build will be finished in the next article: How to Build a Powder Coating Oven Part II which will be coming next week.  If you have any questions or comments, please leave them in the comments section below.  Also be sure to read the original Powder Coating Oven article here and don't forget to check out KNJCustomCoating.com, the builders of this powder coating oven.