You cook the part before powdercoating to “outgas” it, basically any trapped contaminants/oils etc will burn off the surface. If you don’t outgas, they will burn off during curing creating fisheyes and other defects in the finish.
Personal rule of thumb for me is outgassing at 50deg over cure temp for double the cure time.
Ya I am familiar with outgassing dont see the need when part is blasted.
Just wondering how you guys make any money with so many steps?
Blasting doesn’t remove contaminants inside the metal it only preps the surface. Any powdercoat operation worth their salt outgasses after blasting or chemical stripping.
I don’t personally sandblast I acid bath my parts so I can’t speak of his time spent, but I personally don’t spend much time on each part it spends it’s time either soaking or cooking while I do other stuff. Only time I handle is immediately after cutting, then quick scuff after acid bath, then in the oven, then out the oven, coat it, back in oven, done. I can do all that in batches so the time invested into each part is less. Costs involved are minimal.
Honestly even if you’re spray painting, for a quality product you should be doing prep on it. I could save time and cut corners powdercoating (plenty of people do) but the product suffers. So it really comes down to if you want to produce quality pieces. Quality pieces can get better prices.
They have these “special buy” units on clearance at Home Depot for $99. The mesh pads works great for sanding powder coat when you have a f up.
I preheat for a couple of reasons, big one is what Teknic said. When I sandblast the compressor is running almost the entire time which puts a lot of condensation through the line and while my water filter catches most of it I can still see it putting moisture on the part when there are big temp changes which happens really whenever the compressor is running because the temp shifts when the air is compressed going into the tank and when it decompresses leaving the nozzle in your cabinet. The second reason is that sandblasting generates a bunch of static and preheating dissipates the static and that helps prevent edge pull on the sharp edges and thin lines on the sign.
It’s not so much for outgassing as cooking off the moisture and static I added while sandblasting.
Good call on the static I hadn’t even considered that part of sandblasting. I know you shouldn’t even blow compressed air over the sign because of static, but never made that connection with blasting
I hardly ever blast anything to prep for powder, I just soak in vinegar, neutralize, phosphate wash, blow dry and paint. if I am in a hurry I may stick parts i the oven to dry.
Up until now everything I painted was for commercial stuff and to large to blast in a cabinet.
I have never had any problems that I am aware of with the durability of the finish product.
Are you getting that moisture to your plasma table? If you see moisture in the air stream thats alot.
I run my blast cabinet on a different line, the plasma table has it’s own air drying filters. I don’t honestly know if my air to the table is good enough yet, I’m counting pierces on my current tip to try and gauge it. I’m at 340 on the current tip and electrode, if I get 500 I’ll be satisfied although I know it can be better. Maybe this summer I’ll build that big copper tubing air dryer setup someone posted in another thread. I’m using an M60 for the plasma air. I’ve tried the vinegar with mixed results, the mill scale stays on unless you scrub it off for me and I’ve only really had success scrubbing it off while still submerged in the vinegar otherwise it just seems to smear. However, I have had luck sandblasting after vinegar, that seems to make it come off really easy in the cabinet. Right now without vinegar it’s about 25-40 minutest to blast the mill scale off the public facing side of the sign with no vinegar depending on how much surface area there is (some signs have tons of dropped square inches some not so much) and about half that after vinegar soak.
I forgot who mentioned that cooking helps dissipate static but they were right. I had a sign that was edge pulling hard, nothing I did was solving it and I cooked it, resprayed it and just like that the problem was gone so whoever that was thank you!
How long is it soaking?
I might try some stronger vinegar and mix with water.
You can get 45% on Amazon and mix it up at 6-7 %
That may give you better and faster results.
I think once you get the vinegar to work like it should you won’t have to blast.
If you have 30 mins into blasting a sign there’s no profit left at least at not what I see signs go for
I soak either 3 hours or overnight, same results with both. Never less than 3 hours though.
I let it soak a day or two and it washes off without any effort.
I’ll try going two days on my next soak, you don’t have any problems with pitting? I soaked a rusty chain once for 2 weeks and it was severely pitted from the acid.
No but I’m only using vinegar. It looks rusty but still works.
I have left stuff in vinegar for several days no issues. I would say the chain already had the pitting there.
I have left stuff in Vinegar for 4-5 days no pitting. If you soaked stuff in Vinegar and had pitting it was because the Vinegar ate away the rust that was filling those pits.
That’s a relief, existing pitting was certainly on the table as the chain was 100 years old…
The last in the line of unofficial official service branch seals is up. I made a few changes from my original version of this seal and then covered it in super matte blue. This one can be tricky because those really thin outside borders can edge pull really hard, this design needs to be preheated because of it.
I finished a version of the Eagle Flag created by Aidan on Fireshare, it turned out really cool so I’ll try and get that up in the next couple of days.
Have you noticed problems on edges more with some color than others?
I just did some with a very glossy bright Red and it pulled from the edge a little, I have never had a problem until these red parts.
I read that powder quality, and color play a big role and preheating also helped. I really hate adding another step to the process by preheating.
I would like to try some Tiger Drylac and see if there is a improvement with better quality.
