Used the new gun to paint the truck again

[Beck]

I used the new 43430 gun to paint the truck again. I had atomization problems. I got a lot of orange peel. I don't know quite what I did wrong. I painted part Fri night and the other part Sat. After the orange peel problem on Fri I tried thinning the paint some on Sat. It ran. I waited a bit and wiped the runs off with thinner. Then I let it sit for a while and sanded those spots. I tried again without pulling the trigger so far. No more runs, but it still has orange peel. I'm wondering about the gun settings. I used Sum's settings but have a problem about setting the regulator. It says to turn the air up until it sounds like the pressure doesn't go up an more. My hearing sucks. I think it is there but maybe not.
I had another problem where I sanded, or wiped with thinner, througth the paint to the layer of other black paint below it. It shows rings at the sand through areas. There are a lot of them.. This won't get a "best paint" award. I just wasn't picky enough about the prep. In the back of my mind I think it is a rat rod driver. Then when the paint is on I think that it isn't good enough.
I am going to call it quits on the paint and drive it. One bad problem I am having is the satin black paint. When you have a little goof you can't fix it. If it was gloss black I'd color sand it and buff it. All would be fine. If there was a little spot needing paint I could repair it. With the satin black your stuck. I don't know how to do any small patches on a panel. If you spray a little spot you get a flat ring around it from the edge of the spray pattern. It might get color sanded and "finished" with Scotch Brite.

[1FATGMC]

How much pressure are you using at the gun??  Was this clear or single stage??

Try more pressure at the gun.  It has been a while since I used mine, but I think I was as high as 60 psi. at the gun for the clear.  High pressure will atomize the paint better.  I would start at least in the 45-50 range.  Don't forget that an HVLP internally regulates the pressure down.  I see people that think it sprays at 12 psi and reduce the regulator on the gun down to that and it won't work.

Maybe John or someone else will help out on this also.  The one knob you were talking (listening about) can control the amount of air to the gun.  You don't want it restricting the air.

c ya,

Sum

[purplepickup]

The instructions on Sumner's website are very good.  Do you have an adjustable regulator inline before the gun?  It should be set between 50 and 60 psi like Sum said.  Make sure you understand where the three adjustment knobs are on your gun and what they do (fluid control, fan adjustment, and gun pressure).  It sounds like you might need to adjust your fluid control in a little (less paint) and check the fan adjustment (spray pattern).  If you have 60 psi coming into the gun you need to adjust the gun pressure on the bottom of the handle per Sumner's page.  

Do some testing on something to check for atomization, flow, and pattern and fiddle with the adjustments until you get the results you want.  If you just need to get familiar with the adjustments you can put cheap solvent in the cup to play....it's cheaper than paint.  Once you're comfortable with changing adjustments put some paint in and dial it in.  Good luck

One thing that gives me fits is that sometimes my thumb will bump the fan control knob and I don't always realize it until the paint starts to screw up.   :?

[WZ JUNK]

I think that in your case George has mentioned the things that should solve your problems.

On a related note, I had a long visit yesterday with a man who has been a factory paint rep for many years.  He told me that most of the problems that everyone is having with the HVLP guns is that they are not using a large enough air hose and lines to supply the gun correctly.  It is called high volume, low pressure you know(that has to do with the air supply is how I take it).  He says that anything in the system that restricts the size of you air line is going to cause you a problem with these guns.  I am going to replumb a dedicated line for my gun that is bigger and I will use a special Sharpe disconnect that is less restrictive than the Milton ones that I use on my air tools.

I really like the HVLP guns but I think I can get better results than I have had so far.  

John

[kb426]

I have found that I had to put tape over the control knobs to avoid changing settings while painting and not knowing until I had a mistake also.

[1FATGMC]

I think...........  He told me that most of the problems that everyone is having with the HVLP guns is that they are not using a large enough air hose and lines to supply the gun correctly.  It is called high volume, .................John

Good point John.  Seems like I've read that some of the regulators that you screw on the bottom of the gun are a lot more restrictive than others and I wonder about the one that comes with the HF gun.

c ya,

Sum

[Beck]

I know what all the knobs do. I had the regulator on my compressor set at 90 psi. I am using 3/8 rubber air hose. I set the regulator on the gun at 50 psi with the gun flowing air. I set the fan adjustment as the instructions said. Widening the fan would have made the "striping" problem talked about below worse. I did play with the flow control some as I was spraying. I had to turn down the flow the 2nd day when I thinned the paint. The paint was Kirker Hot Rod Black which is a single stage acrilic urethane. The runs the first time I painted with this paint with my old non HVLP gun were from trying to get the paint to flow on the surface and not orange peel. After finding flow problem with the old gun, I was hoping this new gun would atomize the paint better to eliminate that problem. It didn't I had a few small sags with the unthinned paint but it still didn't flow on the surface to eliminate the texture. That is when I figured the paint just needed to be thinned. I had several major runs trying to eliminate the texture with the thinned paint. I stopped and just cleaned the mess up while wet. Then I sprayed it like I would with base coat. No more runs but plenty of texture. This paint is very touchy with "striping" on the fan overspray. It needs to all be wet or it will "print" the fan overlap. A buddy had a station wagon done with this paint. I thought the painter could have done a better job because I could faintly see the "stripes". Now I think he is a pro. I knew there was a problem with "stripes" and couldn't avoid them. He didn't know that character of the satin black and you have to be looking to see them.

[WZ JUNK]

Another tip he told me was to make up a T fitting with a pressure gauge that will plug into the line just at the gun.  Use the reading on that gauge to set your pressure at the gun and then remove this T when you have the gun set.  Of course the T will have to be made up with larger size fittings also so as not to restrict the air flow.  He said that 3/8 " line is not big enough to flow the volume of air you need.  The other problem is that the fittings on the 3/8" line are smaller than 3/8" and they will restrict the flow even more.

I will be painting some this week and when I do I plan to do away with the currently regulator that I am using at my gun.  I will use the regulator at the drop to set the gun.  I want to see if that helps before I change out the air hose.

John

[38HAULR]

One area overlooked is the diameter size of the airline and length, which will determine what you end up with at the gun after doing your regulator settings.  Somewhere there is a formula that can be used to calculate drop..........Frank. .

[Mac]

Somewhere there is a formula that can be used to calculate drop..........Frank. .

I found this table in my auto painting book. It's a little dated; first copywrited in 1965.

[38HAULR]

Somewhere there is a formula that can be used to calculate drop..........Frank. .

I found this table in my auto painting book. It's a little dated; first copywrited in 1965.

That,s the ridgy didge there Mac. Handy info,will copy that for my shed cupboard door..........Frank.