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Friday we tested the King Coat gun at Auto-Cycles facility, which is close to ours. The first piece we tried was a pipe that was coated in Safety Orange. We attempted to spray Purple Starlight over the Safety Orange and got back ionization which you can see in the videos once I find out how to transfer them online. We switched to a Gema gun with a different powder (Mirror Black) and got the same back ionization. I placed a phone call to a chemist from a major powder manufacturing facility, and he said that second coats in this type of weather will actually cause the powder to hold a higher charge. He said to lower your kv's as low as possible (just enough to have powder attract to the substrate), turn your air and powder volume up as high as possible, stand farther back from the part, and move your gun quickly past the part. This will cause more powder loss and a lower transfer efficiency, however in weather like this it is the only way besides hot flocking to get the powder to stop back ionizing. We did this and it worked great. We were able to get 3 coats on cold with the King Coat Gun: Safety Orange, purple Starlight, and a final coat of Red Transparent. I have videos of the whole process and will post in this thread as soon as I get the information on how to transfer the videos from my computer.
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Re: KING COAT GUN TRIAL
Good info for everyone, no matter what gun you use. This humidity is a killer! I was having a bit of the same problem on that bike frame on the 3rd coat, but used the same technique and it turned out well.Dan
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I carry a gun because I'm too young to die, and too old to take an ass-whoopin'! -
Re: KING COAT GUN TRIAL
So the humidity is the culprit, what % would be a good number to stay below so no special techniques are required to get a good coat? What was the approx % humidity when you were doing these tests?Comment
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Re: KING COAT GUN TRIAL
Hmmm, humidity definetely makes sense. Anytime I have back ionization, its been pretty hot and muggy out. This weekend when it was nice, not humid at all, I was able to do 3 cold coats on a test VC.Comment
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Re: KING COAT GUN TRIAL
Auto-Cycle has a PPG humidity gauge and it read 50-55%. There is no real % that is safe that I would know of, when you are having back ionization problems try those steps and that should fix your problem. Even with our kv's so low we were still able to apply 3 coats cold. We did have to fill the cup up a few times but the finish was very impressive.Comment
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Re: KING COAT GUN TRIAL
So humidity might not be the culprit? 50% is pretty low - I think....Comment
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Re: KING COAT GUN TRIAL
Weather conditions were low 90's with humidity in the 50-55% range.
I want to say thanks to PBTP for coming in and helping work through this issue for everyone. I usually just go ahead and spray with the part warm when I have these problems but the night before Matthew came I had a bad problem with the back ionization and he came right in and went to work getting info on how to resolve it.
JasonComment
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Re: KING COAT GUN TRIAL
The temperature could of been the major factor, I am getting the chemist to write up exactly what happens in those conditions to post for you guys.Comment
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Re: KING COAT GUN TRIAL
What EXACTLY is fluidization? I don't think I'm perfectly clear on that....Comment
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Re: KING COAT GUN TRIAL
Fluidization is Da bomb for coating.... HD has a good info on it^Originally posted by JNZFinishing
This one is for you King :PComment
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Re: KING COAT GUN TRIAL
In a hopper there is a membrane. This membrane allows air to pass, but powder will not. Air is fed under the membrane at low pressure, 5psi or so. The powder is on the top of the membrane. The air flows up and through the powder, jently lifting and making the powder "fluid" The powder acctually flows and moves like a fluid. It looks like its boiling in the hopper. And if you put your hand into it, it feels like cool water. Not a solid clump of powder like it is in the container.
Fluidizing is really benificial for Metalics and such as it keeps the powder and flakes well mixed so it sprays with an even cosistency from start to finish. I love my hopper. I acctally will, in most cases take the extra clean up time required for my hopper fed Nordson over my cup gun.Comment
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Re: KING COAT GUN TRIAL
Well la-dee-flippin-da!!Originally posted by banditpowdercoat
Some of us only have cup guns.
Good explanation of the process though, thanks.Dan
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I carry a gun because I'm too young to die, and too old to take an ass-whoopin'!Comment
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Re: KING COAT GUN TRIAL
Ohh, a Wiseguy Eh....Nyk NykOriginally posted by wiseguyzWell la-dee-flippin-da!!Originally posted by banditpowdercoat
Some of us only have cup guns.
Good explanation of the process though, thanks.
LMAO. I know a few people who converted their cup guns to a hopper style. Also, you do have fluidization in your cup gun. When you hit the trigger, the air will fluidize the powder and out the tube it goes. Just not a constant fluidization.Comment
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Re: KING COAT GUN TRIAL
I don't know about your Nordson, but my Wagner only fluidizes the powder in the hopper when you pull the trigger. That's when you set the amount of boiling that you want, AFTER the trigger is pulled, then it stops. I can do constant fluidization, but I have to hook up a direct air line to it.Comment
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Re: KING COAT GUN TRIAL
Hey WISE! My Wagner cup gun has a fludizing membrane and fluidizes very well.
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