HVLP tip size

[John Erickson]

I just bought my first HVLP gun ( Devillbis GTI 620G HVLP ) and would like to know what size tip gives you the best results spraying post cat lacquer ( ML Campbell Krystal and Resistant )

[Wayne Lomman]

My favoured tip size is 2.0. Occasionally I will use a 1.8. I use these for everything from fine lacquers and urethanes to heavy epoxies. This will no doubt cause consternation as some people think this is a cannon but this does everything and has done for me for about 40 years. You can adjust a decent capacity gun down to spray finely, but you can't open up a tiddler. That being said, the Devilbiss you refer to probably only goes to about 1.5, so get that one. Cheers

[John Erickson]

Thanks Wayne, the gun come with 1.3, 1.4 and 1.5, I thought I'd try the 1.5 and see what results I get. On there website they supply up to 1.8 for the gun. The inlet pressure is between 4-10 psi.

[Wayne Cannon]

Homestead Finishing has a nice guide on their Web site for tip size versus viscosity for HVLP.

[Wayne Lomman]

With regard to viscosity, this is something that is a variable controlled by the sprayer. It can and should be adjusted depending on air temperature, substrate temperature, relative humidity etc. I use a single spray gun tip size and adjust the fluid and settings to suit. I should add that I set up my spray gun differently to anyone else I have ever worked with over the last 40 years so feel free to ignore how I do things! Cheers

[John TenEyck]

Wayne, what benefits are there to using a 2.0 mm N on low viscosity finishes? Thanks

John

[Bill Adamsen]

I have sprayed Krystal with excellent results with a 1.7 HVLP (cannot remember the pressure setting, it is a gun I no longer use regularly). I suspect I would go lower with a tighter fan if I used it again (which I won't). Krystal is very sensitive to final film thickness so you will need to card it wet or somehow analyze how much material you are depositing or else hope you are within spec. From memory (you will need to verify) the specs say 6 mil total is max or expect failure.

[Wayne Lomman]

John, there are no particular benefits to using a 2.0 for low viscosity finishes. It's just that a larger tip is no barrier to using low viscosity products. (However it is pretty ordinary putting heavy product on with a fine tip.) My auto painter mates howl with anguish at my set up until they see the results. I was never given options for spray guns when I was learning so it was develop technique or find another line of work. Cheers

[Jim Becker]

One thing to consider here is that tip/needle size isn't the only factor in play and that the various tip sizes have to be evaluated for a specific gun. "In general", it's easy to discuss and assume that a given tip/needle size is appropriate for a given finish, but how the actual gun works will affect that choice. Be sure to test the combination with a particular finish the first time so that you are clear on what works and what doesn't.

[Edwin Santos]

One thing to consider here is that tip/needle size isn't the only factor in play and that the various tip sizes have to be evaluated for a specific gun. "In general", it's easy to discuss and assume that a given tip/needle size is appropriate for a given finish, but how the actual gun works will affect that choice. Be sure to test the combination with a particular finish the first time so that you are clear on what works and what doesn't.

+1 on this. I have a Fuji HVLP system and to Jim's point, even within the Fuji line, they make different recommendations on tip/needle combinations for different guns. Maybe you should just email the manufacturer and ask their recommendation if they did not make it clear in the literature or their website.

[Justin Ludwig]

Start big and move down and until you can't get the wet film you desire. There's too many variables between viscosity, air temps, tip and needle sizes, and air flow to just give a blanket statement on sizes.

The only thing I enjoy spraying through my FLG 4 is stain or thin materials. I use a Graco 9.5 turbine with a #4 tip for lacquer. I thin material 15% and add 3% retarder regardless of humidity. For me, that lays down the best and the retarder prevents solvent pop when it's warmer.