Spray Finishing - HVLP v. Airless v. Air-assist

I'm just starting to research a legitimate spray finishing system and was immediately surprised to read that HVLP is no longer the king of the hill. Now I've got Kremlin Airmix and Asturo on the mind, not to mention airless if I don't mind the hard edges or something. I'm not sure what my question is, if any, other than I think I'm going to be spending some time on the net and was hoping some of you who've already done the research may have some links for me. Thanks.

JP

************************** I want it all.
Reply to
Jay Pique
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Reply to
nospambob

That's Jeff Jewitt's site IIRC....I'll definitely check it out. Woodweb has some good forums too, which is where I started to suffer from information overload. It looks like there was a book published back in 1996, but I've got to figure a lot has changed since then. Probably couldn't hurt to arm myself with that knowledge though.

JP

Reply to
Jay Pique

Perhaps an over-simplification, but.... A LOT of my spraying headaches went away when I switched over to pot-feed. Aside from a few line-losses when cleaning, to be in control of the material feed is a treat.

What I do, is turn off all the air at the gun, but leave the air-supply to the pressure pot (both 2litre and 2gal pots) on. Then I pull the trigger and watch for a nice stream of lacquer. If I shoot the stream from chest-height, the stream lands about 4 feet from my feet. Then I turn on the air at the gun, blowing that nice stream of liquid to a nice fog and adjust the fan shape. Then I throw the two hoses over my shoulder and I can spray inside a cabinet, upside-down in small quarters. That worked best with a proper DeVilbiss HVLP gun. (not cheap).

Most guns allow for a potfeed...even a gravity fed gun can be fed by a hose from the top.

In a word:... syphon feed sucks.

My opinion.

r
Reply to
Robatoy

Jay Pique wrote:

Reply to
nailshooter41

wrote

I have snipped most of Robert's post but included his info on the Fuji Q4. My research wasn't nearly as exhausting having consisted mostly of word of mouth, tool reviews and information gleaned from web sites. I have the same unit and have had the time to do quite a bit of testing. I concur with all of Robert's remarks. I have several photos of the unit and some of the tests I did if anyone would care for me to e-mail them. (you will need a broadband connection) I have no connection with the Fuji company other than as a satisfied customer.

Max (e-mail address should be obvious, remove the "not".)

Reply to
Max

Just to correct a few things re: AccuSpray's HVLP guns

  1. they now have a siphon gun
  2. they make a pressure pot for their AccuSpary 10 gun
  3. HVLP turbines heat the air as they compress it and that air can make an aluminim gun quite warm, if not downright hot. AccuSpary's Delrin gun ( the fluid path inside being stainless steel ) doesn't conduct that heat to your hand.
  4. drop an aluminum gun and it can crack - not so the Delrin gun.

The duty cycle of an HVLP turbine is affected by its motor cooling and its bearings. The former is a function of the units air filters (plural) - one for the air going to the gun and one for the cooling the motor. If the filters are difficult to change you're apt to only change them when the turbine performance falls below a useable level. By that time the motor and bearings may have been damaged, assuming the unit used bearings rather than the cheaper bushings.

The AccuSpray 230 three stage turbine has a duty cycle of

4 continuous hours of use. The 230 puts out 110 cfm at 7 psi (one of, if not the highest, psi of the turbines Robert covered).

just some more things to think about when selecting an HVLP system.

The April/May 2006 issue of Wood magazine had an evaluation of 10 HVLP systems.

charlie b

Reply to
charlie b

A good jumping off point to start looking, but it had many inaccuracies as verified by my personal conversations with factory reps from Accuspray, Turbinaire, and Fuji.

For example, they stated that the Fuji would not shoot a one inch width pattern. Untrue. I have photographic proof from Max from above who took the time to test, measure and mail me some great pics. Thanks again, Max.

They tested the ability of shoot unthinned products and thought that was a very important point in deciding the value of the guns. Every single rep that I talked to told me that they wished they had not used that test as they felt like people would think that they could simply put finish in the gun and start spraying.

They are anticipating returns and the possibility of lots of time with tech support working folks through unsatisfactory finish. This will really be a problem with folks like me that are used to spraying with high presssure as there is never a problem with atomization (with properly prepared material!). It will not be the gun or system's fault, but rather a poor test that leads to incorrect conclusions.

All told me "thin as usual". Since HVLP delivers bigger droplets of finish, you almost have to thin in order to get the material to lay out correctly. As charlie b pointed out, the turbines generate warm air, and this further speeds the drying of your finish. If you don't thin or retard in some way depending on your finish, you will be spraying warmed, large droplets onto a cooler surface. It may lay out some, but not to the potential of the material when properly thinned.

If they wanted to test the power of the turbines (of which Fuji, Accuspray, Turbinaire, and Apollo all use the same Amtek Lamb) and their different configuration they should have used the Oreck test and tried to pick up a bowling ball by connecting to the other end. It would have had the same relevance. Maybe more.

As with any major purchase, it is always important to do the homework you need to do before purchasing. But nothing beats talking to and handling the products. Simple phone calls to the tech support of some of the companies in the magazine article changed my ideas of what I read. Best of all, they were able to tell me where I could see their product in my area. It took three months to be able to handle all the guns mentioned in my earlier post, but it was worth the wait and aggravation.

Robert

Reply to
nailshooter41

Thanks for all the feedback everyone. My initial hope was to get a single portable system that would handle all of my finishing needs. The ability to spray latex paint is important, and the thicker the better so I don't have to use multiple coats. This pushes me towards airless, I believe. But I also really need the ability to lay down flawless clearcoats as well. Something tells me that I can't go wrong starting with the Fuji Q4 as a pretty good all around unit.

JP

Reply to
Jay Pique

RE:The April/May 2006 issue of Wood magazine had an evaluation of 10 HVLP systems.

Ain't that almost always the case? There's almost always a way, albeit sometimes pretty tricky, to make something do what you want it to do - if you want to spend the time finding the way.

snip

Couple of comments

There are water based finishes developed specifically for spraying - right out of the can and some even specify that it's not for brushing on. Some of these finishes even specify that it SHOULD NOT BE THINNED - at all.

I wouldn't want to try spraying a 3, 4 or 5 pound cut of shellac but it's almost expected that you'll thin the "right out of the can" shellac. Not so with poly or lacquer, catalyzed or not.

I guess it's the Expectations vs Reality thing. I don't want to HAVE TO thin any clear finish I want to spray. I don't want to play with viscosity cups or sticks, thin a sample batch, shoot a test, adjust the thinning ratio, shoot a test, tweek the mix and shoot a test - THEN spray my piece.

I HAVE TO adjust the air/finish mix and that takes some test spraying. I don't want to HAVE TO futz with the finish/thinner/ retarder/flow out stuff mix as well.

Ah- but what about the bearings/vs bushings /duty cycle thing? And two filters, one coarser one for the mnotor cooling air and a finer one for the air going to the gun - that's important - to both the quality of the finish as well as the lifespan of the turbines. If they ain't easy to change, one may put off changing them - until LONG after they should be changed.

Given all the clear finishes - and paints - folks want to push through a gun, finding a way to "test drive" the final 2 or 3 choices using the range of finishes you think you might want to use would take some real persuassive talking to store owners or factory reps.

Let's face it, there is no Swiss Army Pocket Knife when it comes to spraying finishes. If you want to shoot thick stuff - get an airless. If you want to shoot clear finishes, any of the HVLP systems in the $700-$800 range will probably meet all your needs. In that price range it comes down to things like "siphon vs pressurized cups/pots vs gravity feed" and "bottom of the handle vs back of the gun vs both" air line connection points and ease of clean up. Depending on what kind of stuff you'll be spraying a finish on, one may be better for you than another.

charlie b

Reply to
charlie b

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