Question
I have recently started spraying with an Accuspray 19 HVLP gun, using a 2 quart pressure pot. Prior to this I used a Turbinaire for almost 10 years. I am having trouble getting a good spray finish while spraying tinted General Enduro satin finish, which I am buying from Homestead finishing. It is very hard for me to get it adjusted to leave a nice even wet coat that looks good off the gun. It usually either has orange peel or looks like it has overspray on top of the finish.
I am using about 45 psi at the gun while the trigger is pulled, and about 5psi at the pot for the pot pressure. I have tried many different settings at both ends, and I still cannot match the finish I was getting with my Turbinaire with the attached one quart can. How can I get a better and more consistent finish? I realize there is probably a learning curve switching gun styles, but I didn't think it would be this hard.
I should mention that the Enduro is a water based varnish, which is tinted to an off white paint color. I should also mention that I was spraying Ben Moore alkyd Impervo last week with the same gun, and although it wasn't as tough to dial in as the water base, it was still a lot tougher for me than it would have been if I had been using my old Turbinaire.
Forum Responses
(Finishing Forum)
From contributor K:
I use the Accuspray Model 10 conversion gun and the Max pressure at the gun is 10. Try lowering your pressure and get the gun much closer. Enduro has to lay out for a while before it settles in. I tend to seal with SealCoat just to be sure before using waterbased finishes.
I don't know what tech support is like for Enduro since General Finishes bought it, but you might try their website. Also contact Homestead as they have good support. Christy at Accuspray is very helpful.
Regarding the gun, I used Accuspray guns and pressure pots with WB and never got great results. I bought a Kremlin for the Enduro job I recently did and it was flawless!
Also find out what the cfm requirements are. I found I had to go to larger hoses and larger disconnects to achieve the necessary cfm. It's the cfm that's going to atomize the finish, not the pressure.
I switched from an Apollo turbine to conversion hvlp about 6 years ago. I'm glad I did for a variety of reasons, but the two systems do spray differently. I found that I need to go lighter with the conversion guns. I never had trouble with orange peel using the turbine but I do with the conversions - hence the need to spray lighter coats. I also use Enduro finishes.
Oh, my pressure pot is set at between 5psi and 10psi - I try to keep it close to 7psi.
It seems that the finish either comes out without being atomized, which I was told would happen if the pot pressure is too high, or it comes out too thin, where it looks like it is only dusting the surface. The interesting thing, though, is how much different this product sprays with the turbine set up compared to the conversion gun.
Contributor A, what is different about the Kremlin system that made the spraying better? I am unfamiliar with this sprayer.
You should be using a 1.4-1.8mm needle and set your fluid pressure to 5 psi. Start the gun off at 10-15 psi at the gun regulator (if you don't have one, get one) and open the needle about 1 full turn. Increase the air pressure till you have a nice fan. Test on a piece of cardboard so you can see the fan properly.
Best plan of attack:
b) Can air cap easily atomize coating? With HVLP gun you need to confirm CFM needs to atomize. If you are running a 20cfm+ aircap - make sure you have 20cfm going to gun. (remember cfm losses here).
c) You are using HVLP gun, that means you should be using 3/8" hose, otherwise cfm losses.
If you can't figure this out on your own, work with a good equipment rep, go over issues and narrow it down.
Let's work with facts and not myths:
- Max 10psi stamped on gun - manufacturers do that do keep compliancy in reference to HVLP ratings. Most mark air caps with max ratings that will keep you in compliancy and/or max equipment performance ratings. Hence, if it is stamped 33psi and your pressures go over that pressure, you are starting to overcome the aircap design and overpowering the atomization zone (blowing it by the zone), therefore the cap is not working within its design. Solution = go to larger cfm aircap.
- Most turbines heat coating. True and not true; different for all manufacturers - they weren't designed to heat coatings but the equipment does get pretty damn hot on most I used in the past. This helps lower viscosity. You will notice that most turbines are using very small tip/needle combos as turbines aren't built for long term production work. Are you using the same tip/needle size? Did you go much larger?
On a side note: contributor J, you maybe slightly uninformed about what an HVLP gun does and how it is supposed to work. The theory behind the technology is to throw more material at lower forward velocities (slow it down to stick more). HVLP does mean High Volume Low Pressures. This is done by CFM, whereas conventional uses higher air pressures. I can get an HVLP gun to dry-spray just the same as a conventional gun, but you must be set up correctly. All production shops in the US are running HVLP air atomization spray (Binks-Dev) and pressure atomization spray (Kremlin). They have to spray high quality and high speed. There are guns out there now with new HVLP technology that are pretty damn amazing (DeVilbiss Compact, Sata, etc).
I took out my old Turbinaire, set it up with a n/n size that was as close as I could find to my Accuspray, and sprayed the same finish on a few test pieces, and they looked great. So my Turbinaire is still giving me a far superior finish over the Accuspray. Thanks for all the input, but I don't think I am much closer to solving this yet. Jeff at Homestead is helping me out on this, and I hope we can solve it soon.
But let's face it, HVLP is not the most forgiving spray technology ever invented, coming from a coatings supplier. It does not atomize as well as conventional, airless or air assisted airless. I have had to change many formulas of products to get customers to be able to use HVLP. I always am looking for the practical use and what its limitations are. HVLP has more limitations than other systems, in my opinion. And this comes from an ex-coatings supplier.
