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Airbrush losing pressure - Help!


ThirstyBob
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So today when I started airbrushing, I noticed that after I sprayed a bit the pressure on the tank was dropping, which made it difficult to get an even coverage. I'd start at around 15psi, and it would hold for a couple seconds, then drop steadily until it was down at 5psi. Turning up the pressure did not help, it still dropped psi. I took out the needle and checked and cleaned it and the rest of the ab, then tried just shooting air through, without needle or anything but the nozzle lever. Same result. Seals are airtight at least until I start shooting air through. I have a Paasche TG-3F, bought it with the compressor in a package deal, compressor has a humidity filter on it.

 

EDIT: Just noticed that while air is going through the airbrush, adjusting the pressure does nothing at all. I can turn it up or down and it stays at 5psi. Unless I reduce the pressure below 5psi, then it goes down. Adjusting the pressure when I release the airbrush changes psi normally.

Edited by ThirstyBob
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5 hours ago, ThirstyBob said:

So today when I started airbrushing, I noticed that after I sprayed a bit the pressure on the tank was dropping, which made it difficult to get an even coverage. I'd start at around 15psi, and it would hold for a couple seconds, then drop steadily until it was down at 5psi. Turning up the pressure did not help, it still dropped psi. I took out the needle and checked and cleaned it and the rest of the ab, then tried just shooting air through, without needle or anything but the nozzle lever. Same result. Seals are airtight at least until I start shooting air through. I have a Paasche TG-3F, bought it with the compressor in a package deal, compressor has a humidity filter on it.

 

EDIT: Just noticed that while air is going through the airbrush, adjusting the pressure does nothing at all. I can turn it up or down and it stays at 5psi. Unless I reduce the pressure below 5psi, then it goes down. Adjusting the pressure when I release the airbrush changes psi normally.

I know this may be a dumb question, but you mentioned a tank and humidity filter, did you make sure the tank and filter's valve releases are tight? I know I have drained my tank and filter, then next go around I get air leaking because I forgot to tighten the valves closed:(

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What kind of compressor are you using and does it have an air storage tank?  Does it normally work and level out at a higher pressure with that brush?  It may be that the motor is wearing out and is having a hard time supplying the pressure to the brush.  Or as Ratmaster2000 said there could be an air leak in the system.  When not engaging the trigger of the brush can you hear air escaping anywhere?

 

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It's an auto shut off tank, it turns on for a few seconds when you power it on, and then turns off until air is released. So if the filters weren't tight, I believe it would turn on every few seconds? There is no sound of leaking either. The Airbrush works fine at first it's just problematic for getting even coats if the pressure drops down to 5psi. Would it be the motor if the compressor has no trouble running without the brush connected?

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It doesn't ever, I usually leave the compressor on with a quick release valve on it that I just slot the airbrush into. Maybe I shouldn't be doing that?

Also the compressor is also a paasche brand compressor, came with the brush. I'll check the model number later.

Edited by ThirstyBob
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1 hour ago, ThirstyBob said:

It doesn't ever, I usually leave the compressor on with a quick release valve on it that I just slot the airbrush into. Maybe I shouldn't be doing that?

Also the compressor is also a paasche brand compressor, came with the brush. I'll check the model number later.

 

You mean you always leave it on or just leave it on when you're using it? If you are always leaving it on and never draining the tank it's going to eventually rust out inside.

 

Your current problem sounds like the compressor isn't keeping up with the pressure demand. Does it take longer to build up to full pressure from empty than it used to? My guess would be a gasket in the compressor or the motor itself is wearing out.

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I'd probably start by using soapy water on all the connection point to verify there isn't a leak somewhere. A third possibility if it isn't a leak would be the regulator controlling the on and off. If it's a Paasche though, and you've had it for less than a year, you should just call them and ask. It should still be under warranty.

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Help!  So I ran into the same problem ThirstyBob had.  Here's what's happening in the best detail I can give:
First of all, I've checked for leaks and there are none.

 

1. Turn on the compressor and the resting PSI (no air being used is 30PSI) at this point the compressor ran for a second or two to fill up and now the compressor is on and not running while holding 30PSI.

2. Start letting out air by using the airbrush and the PSI drops instantly to 22PSI while air is constantly being released through the airbrush (this is the PSI that i want to use) During this time the compressor is running now.

3. After 2-3 seconds of Step 2 above (the compressor still running) the PSI slowly drops down to 10PSI.  This drop in PSI takes about 2 seconds

4. Now my airbrush is only running at 10PSI (way lower than I need)

 

The problem here is that no matter how high i turn the resting PSI on the compressor, my running PSI will always drop to 10PSI when I use the airbrush.  

Compressor: Master Airbrush TC-320. 1 week old (i've been messing with it for 7 days)

Airbrush: Iwata Eclipse HP-CS.  1 week old also

 

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1 hour ago, Highlander said:

Uncouple your brush from the compressor, put a finger or thumb at the end of the hose, and try again.  You can isolate the problem to the compressor or hose or both if you get the same symptoms without the brush connected.

The compressor itself and hose never lose air when i plug the air exits.  
The issue is when I'm running the airbrush and the compressor kicks on. The PSI starts at 22PSI and then immediately drops to 10PSI while the airbrush is still running.  It stays contstant at 10PSI while I have air flowing through the airbrush, but i need the airflow to stay at 22PSI.  

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Is it immediately dropping and then immedately going back up with no wait for the compressor to 'catch up'?  If so I don't think there's necessarily a problem.  

Keep in mind that if the pressure gauge is the one on the regulator, it's reading the pressure in the hose and not the pressure being fed into the hose.  These are different numbers based on how easy it is for the air going in to the hose can escape the other end of the hose, and that 10 PSI may be the back-pressure caused by the airbrush itself and how it constricts the airflow as it goes through the nozzle.

Does the needle instantly jump back up when you cut of the airflow? or does it take time to get back up there?  If it's instant it's just how it's reading an active airflow vs a static one.

It won't be a linear scale either. At 22 psi you ma see 10 psi back pressure. At 44 psi you may only see 13-14 psi back pressure.
 

I'll be honest, 22psi is a little on the low side for airbrushing miniatures unless you're using thin inks.  I tend to run closer to 35-40 on mine.  it could be that's what you're seeing here.

Edited by Cygnwulf
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