Need irgent help. HVLP & LVLP. CANNOT differentiate

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PostPosted: Mon Jan 11, 2021 8:28 am
Hi,

I am not a pro. Just a hobbyist. I needed to paint a couple of things at home and bumbers of my two cars. I have a 2hp compressor. So bought one 1.2mm HVLP gun. I found that its creating a lot of orange peel so did a bit research and came to conclusion that I need a LVLP gun. Bought one today, the store dis not had 1.2 mm nozzle size so I went ahead with 1.4.

Now I tested both with water with the same compressor.

I have a question. I dont have a regulator so I was totally depending upon the gauge on compressor. When I sprayed water with HVLP gun, the gauge reading was around50 PSI. But when I sprayed water with the LVLP, the pressure dropped to below 30 PSI.

Shouldn't it be the other way? I mean of LVLP is using less air, the compressor ahould hav atleast shown the same PSI as with HVLP? Please help

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PostPosted: Mon Jan 11, 2021 10:27 am
You need to read the articles in the Info Center on this site.
Your compressor is way too small to handle a spray gun. You don't have proper filtration or air supply set up to spray paint without major problems.

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PostPosted: Mon Jan 11, 2021 10:36 am
I surely will go through the link. Thank you. I am planning on buying a big compressor. But my concern was the gauge readings. Why LVLP is sucking more pressure than HVLP. If I get the picture clear, I would be able to plan things accordingly.



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PostPosted: Mon Jan 11, 2021 10:47 am
To make it short and sweet Your compressor is to small.
Air compressor HP and Tank size does not Matter, AIR PUMP CFM Matters! Even for a good LVLP gun to work.

Please post what Make and model compressor.
Please post what paint gun, fluid tip, and Air cap your trying to use.
Please Post what Paint you are using, And if you reduced it.

You should not be spraying water through your gun it is pointless.
Water sprays very different than Paint.
Dennis B.
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PostPosted: Mon Jan 11, 2021 11:38 am
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PostPosted: Mon Jan 11, 2021 3:09 pm
Okay, so from all of that we have.....nothing.... What is being shown in print is "pressure" not the single most important aspect of spraying which is....CFM. Cubic Feet of air per Minute is what a compressor supplies. That same CFM is what your guns demand to operate properly. Even the lowest demand LVLP guns are in the 5 to 7 CFM range with HVLP even up into the 12 to 15 CFM range. And your compressor?....wouldn't be surprised if it is isn't down in the 3 to 5 CFM range. The bottom line is like blood pressure in the body. The body can operate in a wide range of pressure however if you don't have enough blood volume you are quite literally DEAD. You need to do a lot more reading about spray equipment and compressors before moving on.....
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PostPosted: Mon Jan 11, 2021 8:27 pm
The simple answer to OP's question (this being different to the answer to his problem), is that every gun creates a certain amount of back pressure as air travels through the passages, valves and even the aircap.

If I take one of my guns, say a Pro Lite, and change aircaps I'll get a different reading at the regulator attached to the base of the gun. That's just with air, no fluid. Different fluids can create different pressure results too.

Now that was with a single gun. In your case you have two completely different guns, probably from different manufacturers and certainly different sizes. So pressure readings will be completely different, ignoring the fact that reading from the gauge on the compressor will be horribly inaccurate anyway.

To make matters even worse, most of the cheap guns sold in hardware stores as HVLP, aren't. Notice the maximum pressure ratings on the guns of 22psi and 43psi?

As for the "Manual testing one by one" stamp on one of the guns, your guess is as good as mine. More than a little lost in the translation perhaps but the difference in etching and misalignment of the lines seems indicate an afterthought. Who knows? It is what you get when you buy guns of this quality, though.

It's hard to tell from separate photos but it looks to me like the holes in the aircap of the "LVLP" gun are quite a bit bigger than those of your "HVLP" gun. Bigger holes means less resistance and therefore a lower pressure reading.

What the other guys are saying about suitability is all quite right, but that wasn't your question.

What also wasn't a direct question but actually led to it was your problem with orange peel. Try this: hold your gun closer, 120-150mm from the panel and move a little faster.
Chris



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PostPosted: Mon Jan 11, 2021 10:16 pm
Thank you so much friends. But these are the most expensive local made guns I can get hold of in my area. Other guns which most of the shops here use cost not more than 20 bucks. I tried to buy what was the costliest on the shelf.

Anyways, I guess I NEED to buy a bigger compressor with atleast 10 cfm of power.



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PostPosted: Tue Jan 12, 2021 11:06 am
I jist realised that the LVLP gun I have. The pic I posted, is Auarita Gun. Are they good or not?

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PostPosted: Tue Jan 12, 2021 11:15 am
Keep in mind, every brand is different.
Every HVLP gun is not always going to take more CFM than every LVLP gun.
One brand LVLP may take a lot for a LVLP and another brands HVLP may take less.
Usually even for the same brand gun, there's really not a big difference to start with.
If a couple CFM's are going to make a difference for you, you're way
to small for a compressor.
You can get some conventional guns that use a lot less.
That's what I used before I had a bigger compressor
and sprayed cars just fine with it.
JC.

(It's not custom painting-it's custom sanding)
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