HVLP compressor question - how much CFM for mini gun??

[cselby]

You have the info in front of you. You want something to maintain 3.5 to 6.0 cfm at 45 - 60 psi. Go with the best rating you can afford.

P

[OneThou]

Never sprayed with HVLP before but just purchased an inexpensive "mini" gun. Its rated 3.5 to 6.0 CFM at 45 to 60psi.

120ml plastic cup with 0.8mm nozzle.

I now need to purchase a compressor and wonder what is the smallest size I can get away with. Only will be spraying lacquer on small decorative boxes, no big cabinet jobs or anything like. Any advice would be appreciated.

Cheers!

[OneThou]

Thanks, I know the specs are there but guess my question should have been, because I'm only spraying small pieces, can I go with a compressor on the small side of the specs and still work ok? I want light weight and portability. Then again, I don't want the thing to run continuously. How many gallons should the tank hold for small jobs like this? Princess auto has a "pancake" style for $144, 5CFM at 40psi, 5 gal tank.

[nailshooter41]

Good advice, but be aware that both sides of this equation are prone to inaccuracy. The compressor you buy may or may not have the "stuff" it says it has, and the gun manufacturers (especially the Chiawanese makers) all all over the place with their specs.

Probably. If you are spraying really small stuff, you may not be in bad shape with that machine. I am thinking that you have that little bitty gun, and they don't take as large a draw as you might think. Besides, the recovery on that compressor should be fairly quick.

If you haven't sprayed with a setup like this before, you will find that the compressor will run frequently when the two items are this closely matched for draw and supply of air. There is an art to that; you can help yourself by opening the electronic off/on regulator box and turning the set screw all the way to one side or another to increase the pressure as high as you can to make the compressor kick on at higher temps. This will help keep the fluctuations of pressure to the gun as low as possible.

When spraying with compressed air, you MUST have a moisture trap, and hopefully a particulate trap as well. Buy a hose for spraying, and use it only for that to keep contaminates out of your spray rig.

BTW, that's a pretty tiny little aircap. I hope you aren't spraying anything more than really thinned products from it. Although it will work with proper thinning and pressure, that's right at airbrush size, not really made for wood finishing.

Good luck!

Robert

[Lew Hodgett]

SFWIW, there are some simple things you can do to help keep water out of your compressed air supply by trying to keep the air as cold as possible during the compression process.

1) A 2 stage compressor is worth the added cost. 2) The larger the storage reservoir (tank), the colder the air which allows the condensate to drop to the bottom of the tank. 3) Use as large a hose as possible since this will reduce pressure drop, thus reducing compressor running time. 4 ) Plumbing.

Forcing the compressed air to change directions will provide a means for moisture to drop out of the air stream.

Come out of the storage vessel with a connection to the "side" of a pipe tee with and the "runs" of the tee vertical.

Connect a large nipple and a petcock to the "BOTTOM" side of the tee. (This is where you will collect and drain condensate)

Connect a 6"-12"nipple"UP" side of the tee, followed by two (2) street ells which creates a 180 degree turn, thus allowing the outlet to point down.

The larger the pipes, the better, but at least 1" minimum.

Connect the hose to this last port.

The above is a simple, but very effective condensate trap.

As long as you remember that compressing air creates heat and hot air holds more moisture than cold air, the easier it becomes to reduce the condensate problem.

Have fun.

Lew

[nailshooter41]

SNIP of good information

I think OP is going for the "cheap" way into spraying. I am sure he is looking at one of those oiless compressor setups that are out there at that price point.

I didn't want to put your comment in about the hose adding more volume as I was sure someone would come along and figure out the length and internal diameter of the hose, then the cubic inches that would add. Then of course others would come along and talk about leaky fittings, etc., that would marginalize the hose volume.

Last year I sprayed an automotive style finish (not buffed, just the urethane enamel) on a large group of exterior doors. I had to spray in their warehouse (they sell doors) as they didn't want the doors to leave the premises. From some reason, my HVLP system and I just couldn't get he mix right no matter how hard I tried. I never did figure out what went wrong, but don't spray enough of that particular enamel to work out the kinks.

So with me at odds with the Fuji, I went home and got my Sharpe knockoff HVLP and set that up to spray. That gun will spray anything.

But I worked my 4 horse compressor to death. It got so hot it was throwing the breaker in the warehouse every 10 minutes or so. Then the reset button on the machine kept tripping if the breaker didn't. That day SUCKED.

Next day: came with 400 feet of 3/8" i.d. pneumatic hose and put something similar to this in the chain just before my spray hose:

solved. The 400' of hose did the trick.

I was able to screw the regulator/water filter unit on the wall for stability. (Nope - didn't put anything in the oiler side!)

You are too damn industrious, Lew. If I worked out of a shop all the time, I would use your system. Maybe...

But that little gizmo (and its relations) above even drains itself when the pressure goes off, and it works great. Screw it on a wall stud or piece of wood and you are installed!

Robert

[OneThou]

Great info guys, thanks to all who responded, I got some good ideas!

Cheers

Joe