Sprayer Adjustment

[Willyou]

I have a small conversion spray gun (gravity feed) that I purchased from TCP Global Corporation a few months ago. I've used it some with mixed success. My biggest problem is not knowing how to adjust the air flow knob at the bottom of the gun handle. I can't find a lot of instruction anywhere. A video I watched said "just leave it alone". Some instructions don't mention it at all. One instruction I have says to close the knob all the way and then listen to the air flow as I open it up until it sounds good. Another is a little more helpful by showing a spray pattern that looks like a figure 8 if air flow is too high and an oval shape if the adjustment is OK. I know that this pattern (oval to round) is otherwise adjusted with the knob on the side of the gun. Can someone explain this better?

[Snipe Hunter]

I have a small conversion spray gun (gravity feed) that I purchased from TCP Global Corporation a few months ago. I've used it some with mixed success. My biggest problem is not knowing how to adjust the air flow knob at the bottom of the gun handle. I can't find a lot of instruction anywhere. A video I watched said "just leave it alone". Some instructions don't mention it at all. One instruction I have says to close the knob all the way and then listen to the air flow as I open it up until it sounds good. Another is a little more helpful by showing a spray pattern that looks like a figure 8 if air flow is too high and an oval shape if the adjustment is OK. I know that this pattern (oval to round) is otherwise adjusted with the knob on the side of the gun. Can someone explain this better?

A couple questions...

Do you know the make and model of the gun? I'd like to look it up I'm somewhat familiar with TCPs stuff.
What are you spraying through it?
What size tip is on the gun (did it come with more than one?)
What are the compressor requirements of the gun...( for example 5-7 cfm @40psi )
What is the rating of your compressor... ( for example 5-7 cfm @40psi )

[Willyou]

In case you didn't count, that's 5 questions.;>)

It is a TCP F3-SET with 0.5, 0.8, and 1.0 tips. It operates with 30-60 psi and 2.5-6 cfm
So far, all I've sprayed is shellac (I think with the 0.8 or 1.0 tip). My current project will be painted with an acrylic emulsion paint (haven't sprayed it yet).
My compressor will put out 6.2 cfm @ 90 psi (not sure what the cfm is at 40 psi)
Thanks

[Snipe Hunter]

Before continuing on, I need you to repeat these three words over and over until they etched in your brain.... Speed And Distance, Speed And Distance, Speed And Distance....

Ok, it's Mini-Gun. We call them "Touch-Up" guns. These guns are ideal for small projects like jewelry boxes, partial panel repairs on cars etc. I use one for motorcycle tanks and smaller autobody repairs.
It isn't HVLP so don't be afraid to run up the pressure to 40-45 psi. To start with, you won't be able to shoot a lot of finish and get a wide fan pattern like you would with a larger gun with it. So you'll probably have to do more passes, maybe slow down each pass.

This particular gun looks a lot like a Kobalt branded gun that Lowes used to sell/ If it's the same gun, it can shoot nice finishes but not do too well with thicker finishes. Some of the other guys here are better suited to help you with tip size and viscosity. I hope they chime in.

The bottom knob is air volume.
Middle is fluid volume
Top is fan pattern.
The Trigger regulates how much air passes through the gun.

Set up a good sized piece of cardboard vertically and securely and fill the gun's cup with water.

Open the bottom knob all the way and forget about it for the time being.
Open the fluid knob about half way and do the same with the top knob.

These won't be your final settings, just a starting point. My guess is that yur fan knob will wind up 80 to 90% open and your fluid volume know only open around 15 to 25%.

Set the compressor at 40 psi. A regulator near the gun will help maintain a constant pressure and airflow. If you use a regulator at the gun, set the one at the compressor a bit higher than 40 psi.

What we just did was establish a baseline.

Now, hold your gun about 8-10 inches from the cardboard. Remember to point the gun directly at your target, not at an angle. Starting off to one side of your target, squeeze the trigger and move across the target past the other side and release the trigger. My best guess is that you want to pass the gun across your work at about 10" to 1ft per second.

What do you see? Is the Fan pattern too narrow? You should get about 5-6" high pattern with a mini gun. I wouldn't mess with that yet.

Did you get the cardboard wet? It should be wet (maybe some dripping with water). You'll need to learn through practice to maintain a wet edge while spraying, but not wet enough to run the finish. It takes some practice. If it isn't wet, open up the middle (fluid volume) knob counter clockwise until you get a wet edge while making your pass. That knob regulates the the flow of fluid to the spray tip. If it's too wet, turn it clockwise until you get your desired effect. Remember, check all adjustments while moving your gun across the work, not holding it still.

To get a wider fan (it will never be real wide on a mini gun), open up your top (Fan Control) knob counter clockwise. That knob controls the volume of air passing through the outside holes on your air cap on your gun which creates your fan pattern. Closed is a straight line, like a squirt gun and wide open is wide (and dry) spray pattern. So play with that knob to get your fan set. I would say that most of my guns are set at about 80% open. Open it too much and you'll a wide pattern with dry edges. You don't want dry edges.

You want to make each pass overlapping the last pass somewhere between 30 and 50% Every finish sprays differently and some don't spray well at all. I've sprayed Deft Brushing Lacquer with about 10% lacquer thinner to thin it to dial in a new gun. Gloss is easier to see the wet edge. It's important to train yourself to see that wet edge while spraying. If you are having trouble seeing the edge of your pattern, hold your arm and gun off to one side while spraying and look at your work from an angle to get a good view of light reflecting off a wet edge. Good light is important. Shoot outside when you can.

The trigger only controls airflow. That's why I said to open up the bottom knob and not worry too much about it because you are actually controlling it with your trigger. But, if you are having trouble controlling the output of the gun, try closing (clockwise) that bottom knob some. As you get more proficient, you might want to open it up again. My biggest mistakes while painting is when I loose my concentration and pull the trigger all the way without moving the gun fast enough or have the gun too close to the work and I run my finish.

OK, so now you have a baseline.

Now practice varying your "Speed and Distance". Speed of your pass across the work and distance your gun is from your work-piece.
I rarely adjust my guns but I adjust my Speed and Distance all the time because I can do that on the fly and don't have to stop working.

Let me know how it goes.

[Willyou]

Two questions:

I'm surprised that "it isn't an HVLP"? Isn't the air volume control at the bottom a distinguishing feature in an HVLP conversion gun?

How do you know when you have the air volume all the way open? I can keep turning the knob counterclockwise until it all comes apart.

Yes. It is a mini gun. I only wanted something a bit larger than an air brush. I rarely have a need to spray broad surfaces. My upcoming paint job will include a lot of small rails and muntins (china cabinet).

[Snipe Hunter]

Two questions:

I'm surprised that "it isn't an HVLP"? Isn't the air volume control at the bottom a distinguishing feature in an HVLP conversion gun?

How do you know when you have the air volume all the way open? I can keep turning the knob counterclockwise until it all comes apart.

Yes. It is a mini gun. I only wanted something a bit larger than an air brush. I rarely have a need to spray broad surfaces. My upcoming paint job will include a lot of small rails and muntins (china cabinet).

An HVLP or "Conversion Gun" will have a regulator at the bottom of the gun. It's basically just a regular old fashioned spray gun with a regulator. Like the famous $19.00 purple Harbor Freight gun. The better ones which were designed as HVLP from the get-go have a larger air duct entering the gun. This allows for more air which allows for less pressure and still getting the same or more air to pass through the gun as a traditional gun. HVLP uses low pressure wind (for lack of a better term) to carry the finish to the work-piece as opposed to high air-pressure. The downside is that HVLP guns don't atomize your finish as well as a traditional gun but most folks spraying wood finishes don't really need that fine atomization because the finishes are more forgiving. A lot of the cheaper HVLP guns are just old Traditional guns with an added regulator to qualify them an HVLP guns. It's still up to the user to dial down the regulator to achieve 10psi or less. My experience is that they don't do well spraying at 10psi unless the gun was engineered for it in the first place. The Sata Mini Jet is an example, but it's $300. That added regulator is basically exploiting a hole in the EPAs HVLP requirements.

Generally it would say HVLP on the side of the gun and definitely in the sales literature. I looked at TCP's site and it doesn't say anything about HVLP for this gun. Adding the regulator just cuts down the pressure but that also cuts down on the air volume entering the gun. If you look at a Turbine gun, which was designed for lots of air, it has an opening as big around as a Sharpie pen. The EPA says that HVLP is only 10psi or less coming out the tip. Most people who buy HVLP Conversion Guns crank up the pressure much higher than 10psi to make it spray well. Especially with thicker finishes.

You'll have to kind of guess as to how far open the air volume is open. Close it all the way and maybe open it 3/8" of an inch?? You can see in the diagram that it only needs to open enough to allow all the air entering the gun to pass through it. If you want, you can close it and run air to it. With your hand in front of the sprat nozzle, start opening the valve until you can't feel any difference. At that point, it's probably wide open.

[Willyou]

I made an assumption that it is a conversion gun based on the presents of the air flow adjustment on the bottom. From what you are saying, there are no external physical features that indicate one is an HVLP. Thanks for clearing that up. But, actually I don't really care as long as I can learn to make it do what I need. As I said, I bought it hoping it would be an oversized airbrush.

Thanks for all your help. I think I now have enough information to learn how to properly operate it with some practice.

[jteneyck]

I made an assumption that it is a conversion gun based on the presents of the air flow adjustment on the bottom. From what you are saying, there are no external physical features that indicate one is an HVLP. Thanks for clearing that up. But, actually I don't really care as long as I can learn to make it do what I need. As I said, I bought it hoping it would be an oversized airbrush.

Thanks for all your help. I think I now have enough information to learn how to properly operate it with some practice.

I always set the air knob at the bottom of the gun wide open on all the guns I've used.  I use a mini air regulator at the inlet of my gun to control pressure to the gun.  Then I know whatever flow that gives me is repeatable from what I did last month and will be the same next year. 

John

[pprobus]

I always set the air knob at the bottom of the gun wide open on all the guns I've used.  I use a mini air regulator at the inlet of my gun to control pressure to the gun.  Then I know whatever flow that gives me is repeatable from what I did last month and will be the same next year. 

John

What John said, but I've only run enamel paint through my HVLP guns.  The only area that I differ is that I use a relatively short (25') 3/8" air hose with 3/8" QD fittings (1/4" pipe thread to 3/8" QD fittings to be specific, I do have "true" 3/8" QD fittings and find the ID to be the same size as the 1/4" pipe to 3/8 QD fittings) and I leave the air regulator at the wall.  The air regulator adds a bit of length to the spray gun handle and can make it awkward to get into tight places, I figure the little bit of pressure drop through my hose and QD fittings should not be significant enough to cause more than a 1 psi difference at the gun.  For a while I was using a short whip (5') of hose with the regulator at the end of the 25' hose, but found that the regulator would get bumped when moving around.  The adjustments weren't getting moved by the bumping, but I figured over time it would not be good for the regulator.  But then at the time I was still using the more widely available 1/4" I/M fittings which added more constriction than the 3/8" fittings I use now. 

But to your question on the air knob, the reason I agree with John is that I found it does very little, especially if you use a regulator to set the correct air pressure for the gun.  Just open it all the way up, if you test it, you will know what point it is open as far as needed and won't do anything else the further you open it, at least that is what I have found with the spray guns I have, and you don't have to waste solvent or finish to make the check, just blow water through it, set it at the point it no longer makes any difference to the spray and leave it alone, you don't need to remove that for cleaning of the spray gun.  Once that is set and you have the regulator set to the proper pressure just make any additional adjustments using the fluid and air pattern knobs.  That lower knob may work if you did not have good control over the air pressure to the spray gun and had to run the pressure higher than the gun is supposed to use.

Just a bit of a disclaimer, I am not a professional painter by any means, but I have been doing a lot of playing/experimenting with inexpensive HVLP paint guns while restoring my DeWally 7790 RAS, after having inconsistent results using rattle cans.  I have a few different spray guns, although mostly the purple $10 HF guns that I have drilled out the fluid nozzles (found the limit to be about a #46 drill bit, just a slight bit above 2 mm, after that the nozzle metal is too thin and crumbles).  WARNING:  Spray guns can be yet another slippery slope.  


Paul

Edit to correct myself: I also ran latex through some of my HVLP spray guns to spray some wall cabinets for my shop, part of the reason I experimented with drilling out the HF nozzles. I even went so far as to buy a Vaper spray gun with a 2.3mm tip from my local Northern Tools but even that struggled without thinning the paint a lot. In short, I don't recommend using HVLP for latex. I understand the airless do much better with latex, although overspray can be an issue.

[pprobus]

An HVLP or "Conversion Gun" will have a regulator at the bottom of the gun. It's basically just a regular old fashioned spray gun with a regulator. Like the famous $19.00 purple Harbor Freight gun. The better ones which were designed as HVLP from the get-go have a larger air duct entering the gun. This allows for more air which allows for less pressure and still getting the same or more air to pass through the gun as a traditional gun. HVLP uses low pressure wind (for lack of a better term) to carry the finish to the work-piece as opposed to high air-pressure. The downside is that HVLP guns don't atomize your finish as well as a traditional gun but most folks spraying wood finishes don't really need that fine atomization because the finishes are more forgiving. A lot of the cheaper HVLP guns are just old Traditional guns with an added regulator to qualify them an HVLP guns. It's still up to the user to dial down the regulator to achieve 10psi or less. My experience is that they don't do well spraying at 10psi unless the gun was engineered for it in the first place. The Sata Mini Jet is an example, but it's $300. That added regulator is basically exploiting a hole in the EPAs HVLP requirements.

Generally it would say HVLP on the side of the gun and definitely in the sales literature. I looked at TCP's site and it doesn't say anything about HVLP for this gun. Adding the regulator just cuts down the pressure but that also cuts down on the air volume entering the gun. If you look at a Turbine gun, which was designed for lots of air, it has an opening as big around as a Sharpie pen. The EPA says that HVLP is only 10psi or less coming out the tip. Most people who buy HVLP Conversion Guns crank up the pressure much higher than 10psi to make it spray well. Especially with thicker finishes.

You'll have to kind of guess as to how far open the air volume is open. Close it all the way and maybe open it 3/8" of an inch?? You can see in the diagram that it only needs to open enough to allow all the air entering the gun to pass through it. If you want, you can close it and run air to it. With your hand in front of the sprat nozzle, start opening the valve until you can't feel any difference. At that point, it's probably wide open.

Actually, the way I understand it, and as I said, I am no pro painter just a curious amateur, is that an HVLP spray gun only puts out 10 psi at the tip as you say, but that does not mean they don't use more pressure at the inlet.  Many of these spray guns that run off of compressed air take a max. of 30 psi at the inlet and internally reduce the pressure down to 10 psi.  The regulator attached to the end only ensures the spray gun is getting the 30 psi or so at the inlet of the spray gun.  My understanding is that there is much more to it than a "regular old fashioned spray gun with a regulator".  

Not trying to contradict you, just explaining it the way I understand it.  If I am mistaken, please correct me.

To complicate matters, there are also LVMP spray guns that run on lower volume, slightly higher pressure and are considered "compliant" in that they meet HVLP "pollution" criteria but can be run with smaller compressors, they are supposed to run at an intermediate pressure between HVLP and conventional spray guns, its these spray guns I think of when I hear "conversion spray guns".  And then there are LVLP spray guns which I have not seen too much information on other than they are supposed to be good for people with portable air compressors but only good for "smaller jobs", but that is assessment from folks spraying autos.  

Thanks,
Paul