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Title: PSA: Harbor Freight Powder Coating Oven
Description: Check the rotary switch connections


JT Metalworks - September 6, 2008 09:51 PM (GMT)
I just picked up one of these ovens for $50 last night and didn't have the means to test it prior to purchase. Got it home, and it wouldn't power up, so I pulled the cover off the bottom to find a crunch blackened neutral input lead.

From what I can tell, the screw wasn't tight enough on the terminal due to under sized wiring off the terminal strip (which also is the epitome of India electronics components: i.e., crap! - which is where these ovens are made).

If you own one of these, you'd be wise to inspect the connections.


I got the oven as a stop gap measure to appease some of my customers who are BEGGING me for powder coating their stuff. I'll still only have $60 into it after the needed repairs/rework, so I'm not bothered by it at this point. That would be rather different had I spent the $350 asking price of retail. If it didn't need a cabinet made, I would've been better off with a curbside supplied unit. Right now, this was supposed to be plug and play. So much for that. At least it's a simple fix.

Pics later, we're headed out to eat.

storts1 - September 8, 2008 02:59 PM (GMT)
Jim,How big a Oven,and doesnt they eat alot of Juice,Thanks,Jack????? :D

JT Metalworks - September 8, 2008 06:49 PM (GMT)
This thing is 18x18x17" inside. The current consumption is pretty low @13A, but since it's 120v, the temp rise time according to the manual (as I haven't fixed it yet) is downright pathetic. So since it will take entirely too long to come up to temp, and recover from temp loss once the door is opened (making production batches impossibly slow), I'm not keeping it.

I'll be selling this on CL as soon as I get it functional again. I probably won't even do any parts in it first.

I have 2 additional 50A 240V outlets in the shop and garage for plugging in a big oven. I was hoping this would fill the void till I got around to building one, but that's not the case. I can't say I'm all that surprised either.

storts1 - September 8, 2008 08:49 PM (GMT)
Jim,Thats what i was wondering? dont you want to do some rims in there?

110,wow,start at 2 am,might be ready,But for 50 bucks,Its still a Money maker! :D :D

JT Metalworks - September 8, 2008 09:00 PM (GMT)
Yeah, rims are possibly a big money maker. The local shops want $75 each. The powder is hardly quantifiable for the amount they need to cover one (fractions of an ounce) and the electrical consumption is on the order of a quarter an hour. So for a little bit of spray time and just loading it in and waiting for it to wet out, there's some good cash potential.

egon - September 9, 2008 03:16 PM (GMT)
Just how high a temperature is required? :D

JT Metalworks - September 9, 2008 04:57 PM (GMT)
It depends on the powder, but typically 375-425F. Nothing too difficult to produce.

I have a double oven coming from a neighbor down the street as soon as he rescues it from the "free" recycling city his mom lives in. I told him I wanted the elements out of it, then 2 days later he says it's gone... If that oven doesn't come back (he now said he's going to deliver it later this week - even though he's only 5 houses down), I hope he never needs any help. lol

I already got the satellite dish he didn't want, and the satellite switch he didn't want (worth about $120, and will work with our service). So I don't know why he thought when I said I would take something he didn't believe me. Although, I can appreciate his desire to get it out of his garage. But if he was that hell-bent on getting it out, I'm a whole lot closer than driving it to his moms. :rolleyes:

Franzę - September 9, 2008 05:56 PM (GMT)
Have you looked into a used food service oven JT? Around here the market for used equipment has hit bottom because so many geniuses will buy wonderful new offshore equipment on ePay. It's funny as hell watching a few flunkeys try getting an oven the size of a large coke machine off a truck and then realize they can't get it thru the door. I watched one sit on the sidewalk for 2 weeks with a blue tarp over it till somebody scrapped it for the owner.

JT Metalworks - September 9, 2008 06:39 PM (GMT)
The stuff I've been seeing isn't the right shape to fit in the space I want it to occupy. The stuff moderately close has all been over priced.

3ph wiring also scares a lot of people off. What they don't understand is that a resistor doesn't know what 3ph is. I could understand if the voltage was off, then you might have problems with getting enough force to push the current, but I doubt that's even a problem because it wouldn't make sense to make high voltage elements and low, you'd just wire up the high voltage models in series.

egon - September 9, 2008 06:47 PM (GMT)
Well heck, that is just nice cooking temperatures. Seems to me we need a design team here as it could be assumed you would want a oven large enough for wheel rims etc.

Now I am going to suggest we start with a box made from galvanized metal to a little larger than the required dimensions. Then build a liner box out of whatever and fill the cavity with ceramic cement. The cement will hold heat and make production runs possible.

Franz will let you know how to hook up and control the elements.

Or go with a galvanized box and wrap the outside with the expensive high temperature insulation. [Can't remember the name of it]

There is a thread on a boat building site where a fellow built a furnace for melting bronze. If I can find it I'll attach directions. It's not nearly as large as what you are looking for but may give you some ideas. :D
http://www.woodenboat.com/forum/showthread...crucible&page=2

JT Metalworks - September 9, 2008 07:08 PM (GMT)
Egon, I don't need a stinking design committee...

I need some time to do it. I'm a full time student (again), have a house to finish remodeling, have wife to keep happy, a kid to raise, and a business to run.

This is the last oven I built:

http://www.veeco.com/pdfs/datasheets/sumo_...p_multi_340.pdf

1600C :P

Franzę - September 10, 2008 02:26 AM (GMT)
Actually, if JT wasn't so lazy, he could cut the insul;ation cost considerably by casting his own in place using vermiculite concrete. He could even add sawdust to the mix and let it cook off outside and smoke the neighborhood up for higher efficiency insulation.

Laundry dryer heaters would probably me more efficient on energy than oven elements.

Now, if we have a design team, we'll need to have working lunches, and a secretary. If we let Storts on the design team the conference room will need to meet ventilation requirements cause Jack farts like a damn volcano.

JT Metalworks - September 10, 2008 05:23 AM (GMT)
user posted image

Mmmm anyone want some extra tasty crispy?

Franzę - September 10, 2008 06:20 AM (GMT)
Lets not be nasty JT, after all the 9 year old assembler did have to make quota so he could get some fried rat for supper.

If he's really good he can work his way up to building welders for Thermal Dynamics or HoFart.

Harbour Frright, bringing America the crap Americans won't make themselves.

egon - September 10, 2008 10:27 AM (GMT)
I see Franz has the "Committee thing" well in hand and has obviously been on them before! :D

The low density concrete Franz has described would be a real good deal! :D And heck, dryer heating elements are not very expensive. I would donate sawdust but the shipping costs would be inordinate. :(

I'm sure JT could assemble a really nice powder coat oven from inexpensive items with no problems. He'd be able to do it in his spare time too. Best of all he could custom build to suit the shape of some of the items he needs to coat. IE: tire rims he did mention! :D

storts1 - September 10, 2008 11:33 AM (GMT)
Jim,Made a few calls yesterday,well a div of where i was calling,and asked for powder coating,,so these are east coast prices,,Starts at 200 Bucks,and goes to "Around 250.00 Ea.!!Rims are getting alot larger in dia,and then the real profile tires! :o

But this place had one of those big arse ovens,where they wheel in 12 rims min!! Guy was saying,these kids all got POCKET fulls of CASH!.Nice chunk of Cash every week!!!--17 year olds,hmmmmmmmmm ,wonder where all that came from,all with 2 cell phones,and a Beeper!(Didnt know they even used them any more) a real entrapenear! :lol: :lol:


My heat dont come cheap,and the lunch room isnt where you would want that!!!hehehehhehhee :D :D :o
Jim,for the hell of it,what does dryier heating elements heat up to?

Franzę - September 10, 2008 03:28 PM (GMT)
The temperature of any electric heating element is around 2000░ jack. The cost of energy and heat transferr efficiency is better on the drier element though because it throws out more infrared heat, and creates more air circulation.

Hell, if yo think electric is high, I just wrote the check for 1000 gallons of #2 heating oil, RED died, $3.299 a gallon. 2 years ago it was $1.869 a gallon. Oh well, Lawn Nazi needs to stay warm, and she won't chop wood.

storts1 - September 10, 2008 04:21 PM (GMT)
Dont remind me,I have 300 gals left,betwen the house and the shop tank,,my guy,whos a Mom and Pop,and they have some other co do there service,and he told me to hold on!! I could take 700 gals,or so,,Hes thinking as it coming down a .25 a gal is quite a bit,and he was as high as 4.05???????crap shoot!!!!!!!??????

PS,Mine was low when i sent you the bill,theve gone up at least 60% since then,and there looking more like 6% they want in January!!!!!!
At least if the machines are running,there making money!! :D Where does all this money go???????? Ct. 4 nukes,No run,,3 i think coal generating plants,No work,,so we buy it all from You and other states!!!!!!!Why so many stuffed shirts?????? :unsure: :unsure:

JT Metalworks - September 10, 2008 04:27 PM (GMT)
The problem is that the double oven comes complete with all the control circuitry. Ease of configuration gets added into the expense factor.

I don't deal with the hoopdy cars, so doing the big 26" wheels isn't something I want to bother with. I'm not getting into this as a discreet business, but as something to add value to my own current work.

I'm not sure what my final dimensions will be, but it will be a profile that takes little floor space and provides at least 5' long part capacity. I do make some jeep bumpers that would be easier to coat than to paint.


Something I've been thinking about in regards to the recovery time between batches - wouldn't using a heavy liner allow for a good amount of thermal mass? Sure, it would be rather expensive compared to using thin sheet (and woudn't be easily formed for the corners), but that might retain the temp better and thus be worth it in the long run. What do you guys think? I'm thinking 3/16" plate or so.

egon - September 10, 2008 08:57 PM (GMT)

A concrete type liner will conform to some unusual configurations and add thermal mass. You can end up wrapping everything with a suitable insulation.

JT Metalworks - September 10, 2008 09:50 PM (GMT)
I swapped out the broken (fan) and burnt (power) switches today and fired it up.

Turns out the owners manual is a worst case scenario. I measured 65-480F in 30 mins.

We'll see what the neighbors double oven looks like and determine this things fate at that point. They got the truck at their house, so it might even be delivered yet tonight.

Franzę - September 10, 2008 11:37 PM (GMT)
I wish you were closer JT, I have 2 electric pizza ovens here that would provide half of what you need, and no use for them.

Thermal batterys are wonderful, they definitely minimize heat loss during load/reload situations. I think a single pizza oven has about 300# of masonry mass in the bottom alone.


JT Metalworks - September 11, 2008 07:28 PM (GMT)
China has claimed another functional piece of hardware. No double oven for me. :(

JT Metalworks - September 12, 2008 04:42 AM (GMT)
Here's a couple shots of the refurbished oven:

My switches - no frills, but they're both rated at 20A. The power leads are still both switched via DPST, but that's just because the switch was the same price as a SPST.
user posted image

The inside:
user posted image

The previous owner was kind enough to include a cooling rack, and it was located on the very top shelf. My guess is that he suspended his parts from it as there's no provisions for hanging anything on the solid sheet that makes up the top.

Franzę - September 12, 2008 07:15 AM (GMT)
Can you make cookies in that thing?

OK, seriously, how long do you have to cook the object being powder coated? Do you have to leave it in the oven to cool, or can you remove it after the powder has melted?

JT Metalworks - September 12, 2008 07:43 AM (GMT)
You can remove it as soon as the powder has flowed out.

I'm not really sure what all I'll be doing in this, but for stuff like valve covers (if they're short enough) I'll just make fixtures that hold the thing from the inside so that they can be rotated just like trays. I've got a vw head out back I've gotta put a tape to and see just how long that sucker is.

If they'll fit, and I can do 8 at a time, that's $160+ an hour to watch tv or work on something else. I know intake manifolds will fit, but those are a little narrower.

I'm planning on coating the electrical box my airco's adapter transformer is getting stuffed into as the maiden voyage for the oven. I just need to plug some holes first as it's a recycled motor starter box. I should look up some KO Lee grinder pictures to see what colors I have. lol

storts1 - September 13, 2008 02:45 PM (GMT)
Franz,Jim,I dont know if you know what a domino's pizza oven looks like,But they Patenened it,its a rotary,conveyer belt job,Thats how they could guarentee 30 mins or free (when they first opened up,)

Dont know how long the powder coat takes,But if you had a ton of stuff,,fire it up once a week,,And I remember you could adjust the conveyer speed,and Just like Pizza's,,Collect them when they come out.there pizza hit another conveyer,and some flunkie would put the right size box,and the pizza would fall right in the box,Tape it,stick a del ticket and into the thrmal bag!!!!! And the driver would usually go out with a min of 5-10 on a fri night!at a shot!And in the beggining,they would have 10 drivers,Hell the world never heard of this!!!!!!WOWWWWW!!


But so many have closed down! just a Idea!!! :rolleyes:

JT Metalworks - September 13, 2008 04:43 PM (GMT)
Conveyor lines are how large scale manufacturing does it. Part of the problem with that is how much space you need to heat to get the part up to temp, and then get the powder to wet out. You're looking at 30mins or more per part. So to have an open end on either side, the heat loss would be enormous. Large operations eat that expense in labor savings, but I'm not doing enough volume to justify that kind of overhead. It's much cheaper for me to rotate batches than it is to pay to heat the room with the oven.

I worked at a pizza hut for 5 days once my sophomore year of HS. They didn't pay enough for the friday night rush work load, so I quit. lol Anyway, they have the same conveyor ovens. It didn't drop it in a box, but they came out the back side cooked in about 5 mins.




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