Air circuits in spray guns

Klleetrucking

Promoted Users
I'm almost ashamed to ask about a HF purple gun but here goes.
Friday I wanted to shoot some epoxy with a Dekups setup on a purple gun. It all assembled fine and no leaks until,,,,, I was about a minute into spraying and then primer started to dribble out from around the lid. I switched the Dekups to another purple gun and the same thing. I noticed the plastic bladder had swelled. It was being pressurized! It would've been a mess of epic proportions had the bladder blown off. I then went back to the OE cup and everything went smooth from there,,kinda.

The next day, I had to find out what was going on. With the lid off the OE cup and some thinner, when the trigger is pulled to the air only position bubbles come up through the thinner hence the pressurized bladder.
I did the same test with my Iwata Bellaria and a HF 60239 gun and no bubbles.
I know, "what do you expect for $15?". I'm just curious as to what is going on.
It would also seem the material in the cup would be aerated with every trigger pull, not good.
 
The nozzle/tip isn't sealing to the body of the gun. You could have build up between the sealing surfaces that just needs cleaned, or you could try tightening it more.

This is one area that really separates cheap from good, the quality of machining and tolerances at which the two surfaces are machined. I know I had to uncomfortably tighten one of my cheap primer guns to get it to seal up.
 
Thanks Sprint.

I may eventually disassemble the purple guns and try what you've suggested. I've had both of them apart in the beginning to clean out the assembly "gel". It was frightening the amount of junk inside these guns from the factory.
I know it's probably futile to consider resurrecting either of these cheap guns but it's a matter of curiosity now.

Yes, the difference between a quality gun and these cheap guns is striking.
 
sprint_9 to the head of the class!
Curiosity got the best of me cleaning up today and I tore down the purple gun and analyzed the how the paint and air mix.
Shamefully, I had never really done this in depth study on any spray gun.
sprint_9 was dead on, I "uncomfortably" tightened the mixer nozzle to really compress diffuser ring. No more bubbles into the material (thinner).
I thought I had it tight enough but not so, and in the air only portion of the trigger pull air would leak from the mixer backwards to the material feed.

Thanks, sprint
 
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