Gun air pressure

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PostPosted: Sun Dec 14, 2014 11:28 am
So when you are given a pressure range that is recommended..how do you determine what pressure is better within that band? I know that when you decrease pressure you decrease atomization and can get bigger dropplets but is there anything else in particular?

I guess what I am asking is what is the effect specifically when raising or lowering pressure? Or even tip size? I have read a LOT but can't find anything specifically addressing this.



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PostPosted: Sun Dec 14, 2014 1:12 pm
lower air pressure it will not atomize properly and you will get orange peel. to much air pressure and you start getting more overspray and wasting material.
no gun manufacturer can say yes you need 55 psi at the gun or you need this tip and everything will be perfect. it just won't happen, not very often anyway. this is just a starting point YOU have to do the fine tuning. what you need to do is get something to spray on old fender or door and load the gun and play with it. set the air way low 30 psi and see what it does. then up the air until it starts to spray smooth. play with the fluid knob and the fan you need to learn what each do and how to use them in combination, it just takes practice. I don't use an air gauge I can test my spray and adjust from there. I won't get into viscosity of different paints and colors but that has a lot to do with how the paints spray
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PostPosted: Sun Dec 14, 2014 5:12 pm
The larger the tip the more material that will flow through it. Hence thicker primers need bigger tip sizes.

What gun are you referring to?
What are the CFM and PSI recommendations for that gun?

This subject gets beat to death and usually because people get confused between pressure and volume. CFM is a measure of volume while PSI is a measure of pressure. Two different animals but both directly influence the performance of your air tools and spray guns.
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PostPosted: Sun Dec 14, 2014 6:49 pm
I watched a video with Kevin Tetz he said to open everything up all the way and let the gun do what it was made to do. But I haven't painted before so I don't know if that's what people really do.



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PostPosted: Sun Dec 14, 2014 7:11 pm
I am using a devilbiss plus for bb/cc and a vaper 2.3 for primer surfacer. Like the devilbiss says 25-35 for basecoat with a 1.2 or 1.3 of 30-40. I am going to be doing some tinkering with a hood here soon so I will figure it out.

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PostPosted: Sun Dec 14, 2014 10:16 pm
Tape a 3' long piece of masking paper on your booth wall.
Before you put paint in the cup back your fluid knob all the way out and then pull the trigger full open and hold it there. Turn the fluid knob in until the trigger starts to push your on your hand. Let go of the trigger and turn the knob in 1/2 turn.

Hook up air supply and pull trigger full open. Set your PSI at the gun for midway in your range (about 30 for that gun).
Put paint in the cup and hold the gun the proper distance from the masking paper. Pull the trigger full open for 1 second and let go. Look at the spray pattern on the paper. There should be full coverage and fine droplets throughout with no runs.

If droplets are inconsistent or too big increase air pressure and try again. If you have runs turn the fluid knob in another 1/2 turn. Repeat until you get a nice shaped pattern with full coverage and no runs.

That gun requires 10 CFM so your compressor needs to put more than that out.
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PostPosted: Mon Dec 15, 2014 4:30 pm
Take a look at the charts listed for each spray gun and each paint manufacturer:
http://www.autorefinishdevilbiss.com/spraygunsetup.aspx
https://www.sata.com/index.php?id=lackdaten&L=11
etc.

Edited on 12/17/14 to correct broken link.
Last edited by 1MechEng on Wed Dec 17, 2014 10:41 am, edited 1 time in total.

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PostPosted: Mon Dec 15, 2014 4:51 pm
1MechEng wrote:Take a look at the charts listed for each spray gun and each paint manufacturer:
[url]http://www.autorefinishdevilbiss.com/spraygunsetup.aspx[/url
https://www.sata.com/index.php?id=lackdaten&L=11
etc.


Those are specific to SATA spray guns aren't they?
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PostPosted: Mon Dec 15, 2014 8:19 pm
I think he meant this site http://www.autorefinishdevilbiss.com/sp ... setup.aspx

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PostPosted: Mon Dec 15, 2014 9:43 pm
You're right. I guess I should have read more carefully before clicking the link.
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