LVLP gun causing headache

[SpitfireIV]

Hi all,

You might be able to help with this query.

I have a Fast Mover LVLP gun, 1.4 tip for doing base coats (I know 1.3 probably would have been more suitable, but, anyway). This was sold to me as being ideal for those with smaller compressors and supposedly uses less paint?

Now, my problem is both the guy in the paint shop and the instruction book says to set the valve pressure at 1.5bar/22psi. I have a wall mounted regulator/water trap that is set to the that pressure but at that, the cellulose base coat even when thinned to 50/50 (for the underside of the car) tends to spit and splutter and is no where near acceptable as a finish, there just doesnt seem to be enough pressure to spray.

I have to pump the gun up to 4-5bar+ before I can get anything thats remotely atomised and fine enough to give a decent coat and even at that its not a very 'wet' coat.

The compressor is a 2.5HP one with quite a big tank, could be 300lt or so. Its given no issues when using a suction fed 1.4 gun with bar coat or 1.8 conventional gravity when spraying primer, but I just cant figure out this LVLP gun. I want to use this for the outside of the car but obviously need to get it working correctly first.

Any help appreciated

 

[ronan]

How long is the hose between the wall reg and the gun ? You might be better off leaving the wall regulator wide open to give full compressor pressure and using one of those mini regs on the handle of the gun.

 

[langy]

All my HVLP guns run at 40psi and then I fine tune at the gun.

 

[ajlelectronics]

The Fast Mover LVLP is rated at 22psi and I have had no problems whatever with mine. It suggests to me that there is a blockage in the air valve on the cup. In fact the FM gun seems to be every bit as good as the DeVillbiss I am using now and without the floor turning sticky with overspray!

If you continue to have trouble, give Fast Mover a ring, you will find excellent service. I called with a query that was me being in pillock mode and their response, because they couldn't understand the problem, was to send me anew gun out FOC.

 

[pedrobedro]

Have you looked at the regulator pressure with the gun trigger open ? A 300ltr receiver on a 2.5hp compressor sounds a bit optimistic, how long does it take to get to pressure ?

 

[SpitfireIV]

Cheers for the help guys.

It is quite a long hose from the regulator to the gun, but I wouldn't think excessively long. Maybe 12/15ft. I dont think its much of an issue though as the suction gun and the conventional gravity dont seem to suffer? The pressure is set with the trigger pressed to release just air.

I did notice some paint was coming from the vent on the paint cup. Can any of you tell me a bit more about this? What its purpose is and in particular the little 'knob' thing that can be removed.

The tank I think is 300lt, maybe 250lt, its a large propane tank, probably could do with a 3hp+ motor on it, but it seems to work fine and hold the pressure for the other guns, just the LVLP that has me stumped.

 

[pedrobedro]

The cup vent is to let air in as the paint level goes down so you don't get a vacuum it should be released when you are spraying. There's something wrong if the cup is pressurising. Take the cup off and put some thinners in the hole where it fits then open the trigger with the air connected to see if it blows back. Are the holes in the air cap clear and is it all tightened up ?

 

[Stu.]

I use this same gun with celly primer and topcoat. At 50/50 it wont spray well at all. It hardly gets out the gun and is dry and unatomised. Thin the paint a little and your troubles will be over.

Mix it 50/50 and try to spray. If its no good just adding a little bit of thinners into the cup, swirl mix it and check on scrap until its right.

Try it, you'll see

 

[richie00boy]

It should spray fine at 50/50, that is the correct ratio for cellulose. Are you sure you have got the air choke adjustment fully open on the gun (next to the air connection)? Also, you will be surprised how much drop you get through the hose from the reg to the gun, you really need a gauge on the gun.

 

[SpitfireIV]

Ok, I picked up a mini regulator and water trap for the end of the gun. Already there seems to be a positive difference, with the wall mounted regulator open fully. Have another other question though....

The air regulator on the gun itself, at what point do you use that to regulate the pressure?

The air regulator on the gun is located at the rear above the grip and can be rotated left or right through 180 degrees. Is it a case that you open that fully and use the knob on the attached regulator set the pressure or it a combination of both to get the desired pressure of 22psi?

Thanks for your help and patience

 

[pedrobedro]

The air regulator on the gun is located at the rear above the grip and can be rotated left or right through 180 degrees. Is it a case that you open that fully and use the knob on the attached regulator set the pressure or it a combination of both to get the desired pressure of 22psi?

The controls above the grip will be the fan and paint delivery (fluid control) not pressure controls. If it has an extra pressure control it will be on the base of the handle next to the air connector. Open that up fully and set the pressure on the wall higher than you need then regulate with your new gun mounted regulator while holding the trigger open. Watch a couple of YouTube videos, it doesn't matter if they are not for your gun they have the same controls giving the same effect. Watch Mario sit ap his spry gan and take note you need a hen spen fen

 

[SpitfireIV]

The controls above the grip will be the fan and paint delivery (fluid control) not pressure controls. If it has an extra pressure control it will be on the base of the handle next to the air connector. Open that up fully and set the pressure on the wall higher than you need then regulate with your new gun mounted regulator while holding the trigger open. Watch a couple of YouTube videos, it doesn't matter if they are not for your gun they have the same controls giving the same effect. Watch Mario sit ap his spry gan and take note you need a hen spen fen

Cheers . But on the Fast Mover lvlp gun the air/pressure regulator is above the handgrip. Turning this seems to have a signifigant bearing on the pressure dial, so was wondering which control was the most important, or is it a case of playing around with both controls and getting the proper pressure?

 

[pedrobedro]

Leave the gun control fully open and use the regulator adjustment so you can see what is on the dial in that case.

 

[SpitfireIV]

Sorry to be annoying you guys but I'm still trying to get my head around this gun!


Ok, I'll try keep it simple, so I wont confuse myself.


Compressor dial is pumped up to 6 bar (event tried it at 8 bar). I have attached a mini regulator to the handle of the gun. The hose is about 10feet long or so. The air reg control on the gun itself is fully open. When I plug in the gun the dial reads the same as the compressor (6, or 8 bar) yet when I pull the trigger it drops to 1 bar or a thick above. I know the instructions say to run the gun at 1.5/22psi, but it doesnt seem to want to budge past the 1 bar mark, even with the compressor flat out. The dial on the gun will raise to 3 or 4 bar if I turn the regulator knob on the gun itself, but at this stage its just spitting.


Popped the mini reg on my conventional gravity gun and I can set that at 3 or 4 bar no problem with the air rg on the gun handle fully open.

So why cant I bump up the pressure a little bit more, say to 2 bar or such with the LVLP to get a bit better atomisation?

 

[richie00boy]

Maybe the gun has a fault.

 

[Stu.]

Yep, sounds like a faulty gun to me too.