Spray gun issue please help! (Resolved)

samueldixon

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Having an issue spraying lacquer with my gun where it starts off spraying just fine for about a min then just kinda gives up the ghost and barely any lacquer is coming out. I can adjust the feed and pressure but it still just won't output enough lacquer to get an even coat. I keep my gun pretty clean and have cleaned multiple times today trying to fix this but keep having the same issue. Works great then 45 seconds later barely anything is coming out.

Using a DeVilbiss starting line gun with a 1.0 needle, spraying acrylic lacquer.
 

Dostradamas

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How much air you pushing through?
Cubic Feet per Minute?
Symptom sounds like you are running out of air capacity.
Everything in line from compressor can limit your air volume.
Compressor cfm?
Air tank size?
Regulator pressure setting and cfm?
 

samueldixon

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How much air you pushing through?
Cubic Feet per Minute?
Symptom sounds like you are running out of air capacity.
Everything in line from compressor can limit your air volume.
Compressor cfm?
Air tank size?
Regulator pressure setting and cfm?
I don't think it's that. It just started doing this, sprayed paint just fine a few days ago. Has sprayed lacquer just fine before as well using the same setup.
 

samueldixon

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eallen

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Is air coming out if the gun but know finish or is air stopping as well?

I have had a few guns that the air pressure control on the bottom of the gun handle is easily turned by hitting it with your hand as you spray thus turning off the pressure. A royal pain.

Not all finishes are the same viscosity thus requiring different pressure to flow so what works for one may not work for another.

Your compressor is one the extreme small end & cfm so is likely running all the time. Check the tank pressure & regulator reading when it stops spraying. If they arent double what you need you are likely getting air fluctuation whether that is this issue of not it will cause uneven spraying.

If it isn't compressor it is usually something still dirty in the gun somewhere. A filter in the cup, a cap, and internal passage way... I fully disassemble and clean when spraying problems arise.
 

samueldixon

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Is air coming out if the gun but know finish or is air stopping as well?

I have had a few guns that the air pressure control on the bottom of the gun handle is easily turned by hitting it with your hand as you spray thus turning off the pressure. A royal pain.

Not all finishes are the same viscosity thus requiring different pressure to flow so what works for one may not work for another.

Your compressor is one the extreme small end & cfm so is likely running all the time. Check the tank pressure & regulator reading when it stops spraying. If they arent double what you need you are likely getting air fluctuation whether that is this issue of not it will cause uneven spraying.

If it isn't compressor it is usually something still dirty in the gun somewhere. A filter in the cup, a cap, and internal passage way... I fully disassemble and clean when spraying problems arise.
Using the same lacquer I've always used.

I'm spraying at about 30psi the tank is usually sitting at 150.

Took the gun apart and hit everything with some lacquer thinner. Everything looked clean but fingers crossed it cooperates tomorrow...
 

chucker

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there are spray gun cleaning sets with a variety of fine wires,, and you poke them through any clogged orifices.
you could try a pin or needle as well.
 

Buckocaster51

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Having an issue spraying lacquer with my gun where it starts off spraying just fine for about a min then just kinda gives up the ghost and barely any lacquer is coming out. I can adjust the feed and pressure but it still just won't output enough lacquer to get an even coat. I keep my gun pretty clean and have cleaned multiple times today trying to fix this but keep having the same issue. Works great then 45 seconds later barely anything is coming out.

Using a DeVilbiss starting line gun with a 1.0 needle, spraying acrylic lacquer.
Well now there then, today you have learned that “pretty clean” is not “really clean”.

;)

Good to hear that you are back in business
 

Silverface

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My compressor is a little underpowered but has worked just fine up until this point. It also just continues to not push any liquid out even when the tank builds back up to full pressure.
I'm dropping in here WAY late, so please excuse me if I missed anything already clarified:

It's actually WAY underpowered for air spray, and virtually impossible to atomize at correct HVLP pressure of 4-10psi. The manufacturer may claim it's an HVLP gun, but HVLP MAXIMUM pressure is 10PSI.

At 30PSI You have to be getting excessive bounceback and overspray.

Visually speaking - how thick are you applying each coat? Initial coats of color should be very transparent and show no flow, which seems weird - but it's not like paint - the general method is 3 VERY light passes make up one thin coat, with the next coat not applied until that coat has fully dried - 30 60 minutes with conventional acrylic or nitro lacquers; sometime a day between oiats if it's a Colortone or Deft blend of lacquer qand oiul-based (alkyd) enamel. Coverage and flow (flow occurring with either color or clears) doesn't start until the third coat.
I'm spraying at about 30psi the tank is usually sitting at 150.
I handled tech service and applicator training for paint companies in the 70's., 80, & 90's and The PDCA/contractors in the 90's - 2010.

WHAT acrylic lacquer are you spraying via conventional air spray at 30psi, at what thinning level (via timing with a Zahn cup) and with what rthinner? For proper atomization and correctly built-up thin (very transparent - no coverage or flow until about the third coat) conventional lacquer of ANY type - acrylic, nitrocellulose or an acrylic/nitro blend - you need to shoot at 60-70psi minimum to avoid tails.

IU did not look up the gun - is it a bleeder or non-bleeder? The former really complicates things due to the constant air flow

But to spray at what the California Air Resources Board, all the Air Districts - and similar agencies in most other states - define "HVLP" as BELOW 10PSI. Most HVLP's operate at 4-10PSI.

It takes (roughly) a 60 gallon compressor that can maintain 80-90 PSI without lag to power an air-spray adapted HVLP gun. Compressor-based HVLP's are so bulky almost all true HVLP guns are sold to be powered by turbine units - compact, low pressure/high CFM units . When spraying at 4-10 PSI you get plenty of material output with excellent control and almost no bounceback or overspray.

Compressor systems are generally used only by contractors for multi-gun operation - but again, they can't exceed 10PSI at each gun's output without violating air quality regulations. AND at 30 PSI they apply full coverage coats - exactly what you DON'T want with lacquer. Any thinner and it ends up a spatter coat.

So I'm a bit curious, if you could indulge me (in the past I've purchased various "HVLP" to test/compare to my Titan Turbine HVLP).

What brand of acrylic lacquer are you using - and have you read the MSDS (it usually discloses the actual type - the label may not)?

How are you thinning it (i.e. via the standard #2 Zahn cup), and is the gun a bleeder or non-bleeder)?

Are you measuring thickness of any coats using a comb or other gage? How is each coat applied - and how does the initial coat appear?

How long do you let each coat dry - and is there any difference between first and last coats as far as how thick?

How long does it dry before buffing?

These are just some basics that sometimes get missed. I want to ensure you're not laying it on too thick and ending up with solvent entrapment - something you may not recognize until later. It sounds like you've used this system before, and I have some concerns about long-term viability.
 

Kurbmaster

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Usually there is a small vent hole in the cap on the paint cup, if that gets clogged it will cause a vacuum in the paint cup and no paint will flow. Just clean it out with some thinner.
You got there first, your solution was my first thought. Back in the early '70s when I was painting cars I just stuck a pop rivet in the vent hole and give it a wiggle before I started spraying. It never left the gun except for cleaning.
 




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