First powder coating, results so/so, anybody use the cheapo HF unit ? Options

[jsteele22]

Last night I finally got around to using the "Chicago Electric" powdercoating setup I bought at HF a couple of months ago. It was on sale, like $60, and others have reported satisfactory results with it. I had some problems, though, and wondered if anyone has any ideas to help.

The problem was that the powder delivery was very erratic. Whenever I pulled the trigger or jiggled the gun the tiniest bit, a huge blast of powder would come out. Huge. I'd say, 1/16" or so of powder would splat out onto the work. After the huge splurt, the powder would come out in a reasonable manner, and go right where it was supposed to. Gradually, though, the fog would get thinner and thinner, and I'd have to shake the gun a tiny bit. This produced another huge splurt, then another interval of acceptable flow. To get by, I had a scrap metal shield that I kept in front of the work until the splurt was over, then moved out of the way during the intervals of acceptable operation. It works, but it's tedious and messy.


The instructions say to either use 10-15 psi regulated at the compressor, or to use the regulator screw on the gun itself. I'm using the shop at my work, and the compressor is off in a different room that I don't have a key for. So I bought a cheapo HF regulator that I screwed onto the gun, and before loading it with power, tried to test the operation. With the trigger pulled, I could - barely - regulate the pressure, but as soon as I released the trigger, the pressure would climb to line pressure. The POS Chinese regulator wasn't regulating. Then, based on the instructions, I removed the regulator and tried regulating the air with the screw built into the gun. No way of knowing the pressure, but from the sound I could hear the rate of flow and trim it to something reasonable. In any case, the air flow is smooth and steady.

Any tips or suggestions ? The obvious thing to try is buy a non-crap regualtor. But has anyone had luck using the metering screw in the gun itself ? My hunch right now is that maybe I had the air flow too slow. How rapidly should the powder coat the work ?

TIA, Jeff

p.s. I'm off skiing tomorrow; won't be back until Tues.

[John]

John you can't get a proper cure that way. The powder MUST be baked within a certain temp range or it will not cure properly. Temp range should be between 400-475 deg. Any lower or higher will cause problems. Higher less so. Lower temp will result in the powder flowing out and looking good, but it will not harden fully and will be easily scratched, chipped etc. Powder is not like paint, the variables can't be changed but so much

Sorry to burst your bubble, but you can definately shoot for the lower limits of the powder for a longer period of time. It's done in the industry all the time to cure irregular parts (or parts with varying thicknesses of metal such as weldments). The key is to get the metal temperature to the cure temperature for the scheduled time.

If one can't slow the conveyor down slow enough at the low end of the temperature range, a lower temperature powder can be chosen (the powder suppliers can even formulate one to work for a given application). Typically, off the shelf powder can be made to work one way or another.

The temperatures are POWDER DEPENDANT. Without the powder curing schedules, you would not know what you are shooting for. You can use "rules of thumb" as you stated, but your results will vary.

If you want consistant surface finish, colors and gloss (especially light ones such as white), then you will definately notice that too hot of an oven will quickly discolor the powder. Overcuring will also have adverse effects on finish, gloss and color.

You left out half of the equation. It's really time AT temperature. The part needs to remain at cure temperature for a given amount of time or the crosslinking will not occur and your powder will not pass a rub test.

We do tesing in our powder application and cure lab for our customers and these are simply facts.

(We sell automated product finishing systems: Ovens, Booths, Application Equipment, Pretreatment, and Conveyors)