Gents

Hoping the more experienced painters on this forum could advise if what my spray gun pressure is doing is normal. The gun in question is a HVLP air cap on an Iwata AZ3 HTE2 primer gun.

I have the working pressure set in the below video at around 27-28psi for demonstration purposes (I normally run 29psi per the TDS). When the trigger is pulled the pressure drops quickly to say 32psi then drops down to the working pressure (27-28 in this instance)

https://youtube.com/shorts/rRz9A28FHCQ?feature=share

Essentially it drops rapidly when the trigger is pulled while the fluid needle is still seated, then as the needle opens the pressure drops down a few more psi. Is this what a normal spray gun does? Or is it supposed to be a crisp drop down to spraying pressure?
I feel like the initial spray will always be atomised a bit more but if its normal then it is what it is.

Regards

Adam

The size and ratings of your air compressor are critical to the spray gun functioning properly.


The following is from the Technical Data Sheet (TDS) that came with your spray gun.

Your gun will require a minimum of 8 CFM (cubic feet per minute) of air at 30 psi in order to work properly. Make sure your compressor puts out that much or more.

Here's how to set up the gun:

You will set the air pressure at the gun while holding the trigger full open. 29 PSI is the operating pressure to start with.

Tape a piece of masking paper on the wall, large enough to set your spray pattern.
With the gun empty back the fluid knob out far enough where it doesn't contact the trigger when pulled full open.
Hold the trigger full open and then turn the fluid knob inward until it contacts the trigger.
Let go of the trigger and turn the fluid knob another 1/2 turn in.

Put some paint in the gun and hold it about 6" from the paper and then pull the trigger full open for 1 second.

Examine the spray pattern. Adjust your fan size first. Then adjust your fluid and air settings to get a full pattern of consistently fine droplets with no runs.

So I have no problem setting up and spraying with the gun...it was more of a question as to whether it is normal for what the pressure was doing in the video - aka dropping really fast to 32psi with the initially trigger pull (which is what I want) but then to drop down a bit more as the fluid needle retracts?

It's not a lack of pressure in this case, just the transition with the needle opening and whether there is an adjustment that may need to be made.

See bold type in my reply.

It's normal.

As you pull the trigger through the second stage the airflow changes inside the gun, reducing the pressure seen at the inlet.

Further adjustment to the actual pressure while you're delivering fluid is up to you and how the gun is performing at that stage. The degree of change depends on the gun, but some of mine I adjust up a little.

Thanks mate.

You can set it up six ways to Sunday, but if you don't have adequate air supply the gun will still not spray properly.

It will start off just fine and then the spray pattern will gradually change due to a lack of volume of air.

I learned this the hard way, which is why I asked the questions you never answered.

Good luck.

the valve on your gun is not a true regulator it just restricts the air flow to reduce air pressure. if you have your main air supply, (the air from your compressor) set a say 120# you going to get that 120# as soon as you open the gun. then it restricts it down to whatever you have the gun set at. try and set your main regulator down to 35-40 lbs. and see what happens. i don't use the adjustment at the gun unless i want to set it for a particular spot I'm going to spray on the job. i set my pressure at the wall mounted regulator then fine tune with the gun valve if necessary. i set the wall regulator and test the spray and adjust accordingly. IF you're going to do much spraying you need to practice adjusting your gun. paint viscosities vary and some will require more or less pressure at the gun. you need to know what to do if something isn't working right. like orange peel typical cause is low air pressure, you need to turn it up a little. overspray and a dry finish, to high needs to be turned down. that setting at that the manufactor put on there is just a starting point, you may have to go up or down from that.
Jay D.

You need Hi Flow air fittings at the gun and Hose and no air regulator at the gun to reduce or eliminate the air pressure fluctuation.
NO air pressure fluctuation is not a good situation. You will F up a paint job quick!!!!

Also where is your Air pressure regulator?
How old is the regulator and what brand? You do not want a cheap China made POS!
Is it on the compressor X feet away?
Do you have more than one pressure regulator in the system?????
Do you have a water trap?
What size pipe is your air system plumbed with?
What is smallest fitting in the system?

Air is everything!!!!!! Jim is spot on

NFT5 wrote:It's normal.

As you pull the trigger through the second stage the airflow changes inside the gun, reducing the pressure seen at the inlet.

Further adjustment to the actual pressure while you're delivering fluid is up to you and how the gun is performing at that stage. The degree of change depends on the gun, but some of mine I adjust up a little.

No it is not normal, Not as described in original post.
A small variation is, But not a radical shift NO 3lbs or more is a big shift when under 30lbs.
This indicates problems with air supply like Jim said.

Many many!!!! different things could be causing this problem.
My system does not do this!

Bad Air Pressure gauge, non hi flow air hose fittings, then Air regulator would be my first guesses as would be restrictions in the system and one of those cheap air pressure regulators with a Gauge at the gun also a no no. Just a strait T fitting of correct size with a gauge No air adjustment! device.

Adjust air at the wall see the air pressure at the gun. If pressure creeps up and down from what its set at Regulator is bad. Like I said No cheap China made Junk.