Need help with HF 43430 HVLP Spray Gun

[ryan.s]

http://www.harborfreight.com/cpi/cta...emnumber=43430

I just picked up one of these today and tried testing it out with some water. I'm using a 15 gallon compressor which seems to keep up okay but what I don't understand is the max psi on this says it's suppose to be 43psi but it doesn't seem to work properly.

Anything below 100 psi gives me drops rather than a fine mist. Also if it's set below 100 psi the value regulator on the gun is constantly releasing air. Is this a defective gun or am I just using it wrong?

Any suggestions on the settings and such would be appreciated.

I had the other HF gun, non HVLP and that seemed to work better. Don't really see a difference with the HVLP.

Thanks,

[jarhead]

Ryan,
I am no expert, but I think it's the CFM output that you should be looking for.
I saved a link to an article that may be helpful to you - scroll down to the "Small Compressor?" section:


http://www.spraygunworld.com/Informa...oodworking.htm

[MBG]

With mine I set the pressure to around 35psi with the trigger pulled.

Have you adjusted the needle? You may be trying to spray too much material. Try closing it all the way and and backing it out 1/2 turn at a time. You may also want to close the valve on the side down all the way while you experiment. This valve regulates the fan spray. I found the fan uses way more air than the main nozzle.

Mike

[ryan.s]

I think I figured it out. I tried switching hoses from a 1/4" nailer hose to a 3/8 air tool hose and believe it or not it made a world of difference. I guess the even though the pressure was there there wasn't enough airflow. Thanks for the help guys.

I posted this on another forum as well and it seems there is a difference between pulling the trigger vs. not pulling the trigger while setting the pressure gauge? I noticed MGB mentioned this as well. Can anyone explain? Thanks!

Jarhead thanks for the link, lots of good info.

[LCHIEN]

I think I figured it out. I tried switching hoses from a 1/4" nailer hose to a 3/8 air tool hose and believe it or not it made a world of difference. I guess the even though the pressure was there there wasn't enough airflow. Thanks for the help guys.

I posted this on another forum as well and it seems there is a difference between pulling the trigger vs. not pulling the trigger while setting the pressure gauge? I noticed MGB mentioned this as well. Can anyone explain? Thanks!

Jarhead thanks for the link, lots of good info.

With airflow there is a pressure drop along a hose that is proportional to the rate of airflow. With zero airflow the drop is zero.
The drop is also proportional to the cross section of the hose, more area (bigger hose) will have less pressure drop per foot for the same flow.

So considering its a "high volume" then the drop along the hose will be substantial with a small hose and less substantial but still quite measurable with a bigger hose.

The pressure at the air gun is the pressure at the compressor regulator MINUS the pressure drop of the hose. With the gun trigger off the pressure at the gun may have been 35 psi but as soon as you pulled the trigger and air flowed the pressure at the gun would drop.

So what you have discerned makes total sense to me as an engineer.

In order to to get the proper pressure at the gun you need a big enough hose to have little or no drop in the hose and then set the correct pressure at the A/C regulator. OR, use a small hose and compensate by starting with a higher pressure, or a combination of both.

You might consider temporarily plumbing a small pressure gauge at the gun until you are familiar with the drops in the hose. Then take it out (I assume it will be something of a nuisance there.)

[ryan.s]

Thanks loring your explaination makes sense. Fortunately the gun comes with a pressure gauge at the base of the spray gun and I do notice there is a drop in pressure once the trigger is depressed. I will adjust the pressure accordingly.

[Andrew Benedetto]

I have that gun and use it for car paint set at about 35psi running.I set the AC regulator at about 100psi. I use a 1/2" hose w. 3/8" whiphose/swivel end and 3/8" QD. Lowes and evn some HFT stores have HVLP Amflo QD that are 1/4" style set that allows better flow than standard 1/4" QD's. The cheap China set HF QD's are not very good for that gun. Put a set together and blow into it, you will see what I mean, lots of backpressure.