What is exactly an HVLP? - created 03-14-2007
Diaz, Victor M. - 03/14/2007.13:15:17
Trying to make American guitars in Flamenco Country
I thought I was sure about this, but I saw an announcement of an HVLP system which used a tankless turbine-based compressor. Is this the rule? Or are there HVLP guns that can be used with a conventional compressor?
Thanks in advance
There are two different kinds.
1) True HVLP which is driven by an air turbine.
2) Conversion HVLP which is driven by an air compressor.
There are various advantages and disadvantages of each kind. I got the conversion HVLP spray gun because I already had a compressor and this style reportedly gives better atomization.
Thanks, in the mean time I browsed a little and saw that there's some debate about the "true" HVLP turbine-based systems and the "conversion" guns that use a standard compressor. I also saw that in some states it's mandatory to use HVLP. I suppose this will come over to Europe in a snap.
Is it true that you can spare up to 40% of lacquer with the HVLP? At the (mainly shipping) costs the lacquer goes,this is no small advantage!
Hi Victor,
Conversion guns behave more like high pressure guns, better atomization and a little more overspray. If you already have the compressor, they are generally a bit cheaper.
Both types will waste less material than a conventional high pressure gun. 40% savings seems a bit generous , but I would believe 30% from a well tuned setup.
Thanks, I'll continue pondering the ideas...
Um, in a production setting, Europe's far ahead of the US in terms of legislating the sale of HVLP (conversion) guns; a lot of the guns sold in the US are illegal for sale here because they're not certified for proper use - SATA guns are (pricey), but I contacted several Euro manufacturers listed on sites like Homestead Finishing (Walcom, Italian maker), and at the time, they couldn't sell me their HVLP conversion gun because it wasn't properly tested and certified yet. May have changed by now. Environmental regulations are pretty tight on anything that seems vaguely professional-use; you can still find some DIY quality stuff around, but not HVLP stuff.
I've got a Sata MiniJet3, great little (expensive) gun, don't regret my purchase for a moment. I did find I got a much better finish (smoother, less bumpy, fewer coats needed to build a good film), far less overspray than with my cheap-and-nasty DIY store gravity feed gun. I don't know if I save 40% over my old gun, but I think it's at least 25%. Like with any new piece of equipment, there's a learning curve to adjusting and using it, so the savings may not kick in quite that quickly.
mattia, what is the air pressure/volume required for your sata?
Um, not a lot? I don't know off-hand, honestly, been too long since I used it, but I think it's about 2 bars, and
My Walcom STM HVLP gun is rated similar to the Sata. It runs best right at 28 psi and I think it only uses about 2 cfm. My 2 hp traditional compressor has no problem keeping up with it. Be warned though that some of the HVLP conversion guns require a lot of air, on the order of 6 to 8 cfm, which is above the output of a smaller air compressor.
IIRC the larger SATA guns like the RP use 15 cfm and the minijets use 8 or 9.
Another popular compressor powered gun in the USA is the DeVilbiss SRI series. Very comparable in the Sata Minijet series but the parts are supposedly a little cheaper.
I guess I should revise my comment then. The Walcom STM is rated at 3.9 to 4.6 cfm so it does require less air than the SATA minijet.
So if you blow a coat on in 30 seconds you might have to wait another minute for the compressor to catch up. For production work air supply is a consideration, for the occasional guitar much less so.
Like Mattia, I also use the Mini 3. Once I learned to use it, I'll never go back to any conventional, much less siphon feed gun.
I view compressors like Dust collectors, and apply the Tim Taylor approach - if you think you got enough, buy more. Even though you may be running at low pressure - 29lbs at the gun, your compressor needs to supply enough volume of air. I finally got smart and invested in an upright oiled compressor. Don't forget the filters!
Atomization on the Sata is excellent, but I don't believe its because its a conversion gun. Personally, I know its the gun itself - my cheaper guns are, well, cheaper. I've seen a 3 stage turbine spray as well as the Sata. Of course, the cost of the turbine equaled the cost of my gun and compressor.
Either way, the HVLP definitely lays more material on the instrument. My floor was sprayed with dried lacquer dust using my siphon feed. Now, almost "nothing" hits the floor.
And, just in case and since no one mentioned, HVLP stands for High Volume, Low Pressure.
So, I take it as "you need a big compressor" for HVLP, at least a big tank. I checked some local manufacturers over here and indeed they talk about "more than 4HP" for HVLP, while you can get out with 2 HP with the conventional guns.
I have to "optimize" my investments, so I would spend the money on the HVLP conversion gun with a small compressor (1,5-2HP with 50 liter tank). Is this crazy? And if it is, should I stay with a top-of-the-line conventional spray gun?
Some years ago, when I was doing the finish work for a manufacturer of instruments, I researched HVLP when we were getting ready to replace the spray equipment. I consulted Michael Dresdner who asked me several questions about the operation, including what material we were spraying and how much material we were using. We concluded that we wouldn't be able to recover the cost of new HVLP equipment in material savings, at the rate we were using finish material, in the life of the new equipment. I was spraying about 3 days per week, 8 instruments at a time.
Dresdner also made the comment that the quality of the sprayed finish layer is dependent on the quality of the tip and nozzle combination, not whether an HVLP or conventional gun is supplying the air to the tip and nozzle.
We bought a new conventional gun.
The claims of 30% or 40% material savings, I suspect, come from studies done with well trained people spraying cars, furniture, or other items larger than most instruments, where the entire spray pattern is 'hitting' the item. Guitars, mandolins, banjos, etc., especially necks, waste much more material because only part of the spray pattern is 'hitting' the item, and the rest of the material sprayed from the gun is going directly into the spray arrestors or filters.
HVLP can save material when spraying instruments, but I don't think one can expect the kinds of savings one could get spraying cars.
I haven't used HVLP equipment since the early days of the technology, back when I was spraying 'boxes' at a cabinet shop, but my impression has always been that the advantages have been over-sold by the marketers of the equipment, and though there will likely be less finish material on the spray room floor and in the filters, there will probably not be a significant monetary saving in finish material. Whether buying HVLP 'by choice' or 'by regulation', know that the quality of the finish still comes down to the quality of the equipment and the skill of the operator. The technology is not magic.
I guess I'll repeat myself. I am running a small conversion HVLP spray gun very successfully with a 35 year old, 2 hp, oil lubricated air compressor. It seems that I use about half as much lacquer per coat. I did not replace my old spray gun for the savings in lacquer costs but for the better quality finish and less overspray to mess up my shop.
So, I guess I'll repeat myself, or paraphrase perhaps.
Unless you have purchase records showing the amount of finish used per month/year/whatever before and after switching to HVLP, you can't really know how much material you are saving.
If you're getting a better quality finish with HVLP, it may very well be because you now have a better gun/tip/nozzle combination and/or more experience and skill, and not simply because of the HVLP. A better gun/tip/nozzle and better skills will reduce material usage too.
Less overspray and less material used are good reasons for considering HVLP when setting up a new system, but if you are getting rid of a conventional system and getting HVLP for those reasons only, that's a pretty expensive way to keep down the overspray in the shop. The other reasons for 'switching'; better finish, etc., just aren't what the sales people say they are, in most cases. Personally, I have no trouble getting a sprayed surface of just as high quality with my nearly 30 year old Sharpe model 90 (now discontinued and obsolete) gun as with any new gun I've tried, whether HVLP or conventional.
Thanks, I'm convinced by the "volume" argument: I would need to do a lot of instruments to notice the savings, so I'll spend the extra money in buying a better conventional gun.
Cheers
Aren't there some legal, or at the least environmental reasons for going with HVLP as well? I have a friend in California who restores old (pre WWII) cars for a living (among other things). We had a discussion about spray units because I was curious about the HVLP turbines coming on the market back about 15 years ago. If I remember right he said that he would be required by California law to go with HVLP and all kinds of other changes to his shop. Material savings in paint for him was essentially piss in the ocean compared to what he charged for restoration, but for legal reasons he'd have to change over. He also felt there was no quality advantage to HVLP over a conventional gun, but then he "grew up" using conventional guns.
I switched from a conventional to a CAT techline Jr mini conversion gun. It's cheaper than the SATA jamb guns but still a very nice shooting little gun. I'm definitely using less lacquer than before, about 25% less. Part of that is less being blown away and part of that, I believe, is that the finish is so much finer I don't have to sand as much off to level.
If it broke, I would definitely get another. Maybe even spring for the SATA. There's no comparison in the finish quality. I can spray opaque bursts (e.g the black on a silverburst) with complete confidence that the atomization is going to be fine and consistent. No surprize spatters like the cheap conventional jam guns.
The Techline Jr works great with a 2hp pancake compressor.
I also grew up using conventional guns, and from a quality standpoint, you just have to learn how to spray each one. Both do great finishes.
Personally, I won't go back to conventional for 3 reasons - overspray, overspray, and overspray. And, until there's a gravity feed turbine, I'll stick with my conversion HVLP. Its SOOOO much easier to clean. Then again, I'm lazy. Besides, I use the compressor for other things, and maybe an oscillating wide belt sander is in my future, then I'll be ready to go! Just my experience anyway.
There is a gravity feed turbine system... Fuji has 4 different turbine systems. Although them come standard with pressure-feed-cup guns, they also offer a separate gravity-feed gun for these systems, and a "conversion kit" that turns the standard-equipment pressure-feed gun into a gravity-feed gun. I have no experience with any of these systems, but have been reading about them, amongst other HVLP turbine systems.
For the record: there's a significant material savings when using a SATA MiniJet, probably because, well, the spray pattern is smaller than the instrument itself. Ergo, less overspray.
I think a conventional gun can be set up for very little overspray if it's of decent quality. That said, the economics work if you are spraying polyurethanes that cost more per quart than some of the guns. Even the most expensive Sata gun looks cheap if you're used to sending guitars out for finishing.
It's been some years since I looked into these, and I never used one, but I think the idea about saving on lacquer is because the HVLP (High Volume Low Pressue, just incase someone wondered...) system has less over spray because of the lower pressure, but lays on a good coat because of the high volume part. So you are not wasting finish that is floating around the room and isn't getting on the instrument.
The reason there is less overspray is that with the lower pressure, the spray comes out fairly slow and so it does not tend to bounce of the instrument. It lays down real smooth onto the surface. I think this would also tend to lessen orange peel.
Gerry, I checked out the Fuji system, and it seems to be, as you stated, a conversion gravity feed. The reason a GF is easier (to me) to clean is that you don't have to back flow solvent (or thinner) from the bottom of a siphon. Not sure if it would be the same on the conversion.
David, I would tend to disagree somewhat regarding overspray. My mini DeVilbiss conventional shoots out WAY more overspray than my cheapo full size PC HVLP. I would consider that DeVilbiss "decent" quality, especially compared to the PC, which was less $$$.
For the price, the new Finish Line versions from DeVilbiss looks like a pretty good deal, probably WAY better than the full size PC (which is a good primer gun, BTW).
Barry hinted at something on the nose regarding pressure. Key to HVLP is atomization, and the Sata has an adjustment for that - not all do.
Orange peel is sometimes the result of too heavy spray, resulting from among other things, too thick material, gun too close, gun too slow, or, here's the kicker, not enough atomization so the particles come out too large.
Be careful, too much atomization, and a dry spray can result. Practice on scrap.
Both have been metioned in this thread.
Can someone explain the difference between the 'oiled' and 'oil-less' compressors, and which type would be recommended?
Oil lubricated air compressors are the old style of machine where there is a pool of oil in the bottom the compressor that gets distributed over the moving parts. Disadvantages are that you have to filter the oil droplets out of the air stream and you have to maintain the oil. Also the machines tend to be heavier due to the cast iron. Advantages are that it runs relatively cool and quite. Also, these have a long life and rebuild kits are available.
Oil-less compressors are a fairly new development that uses sliding graphite plates in the valve mechanism. They tend to be loud and will wear out after awhile. They need filtration to remove the particles of the graphite that wears off. The compressors are light, cheap and there is little maintenance.
Oil-less are good for homeowners that need to move the compressor around for their various work tasks. Oil lubricated are good for a permanent installation in a pro or semi-pro shop that requires more air volume and dependability.
Barry,
20 gallons, which I think is pretty good. I wouldn't want to go much smaller. By the way, I have my compressor hard-piped into my delivery system.
Arron, That's excellent information all around. I've been using the same DeVilbiss conventional touch-up gun and it's tricky to get it set just right where you get a decent amount of material out without overspray and without dry powder. In the end it's probably a lot slower than the newer SRI HVLP gun for similar results.
My first spray gun was a DeVilbiss touch-up gun and I never could get it to work right. I finally got a full size Binks and it worked great. Every once and a while, I would pull out the DeVilbiss and try it again. Never could get it to work. I finally permanently attached it to the wall.
Most lower end guns have two adjustments - air, and material. Higher end guns add in an "atomization" adjustment (on my Sata, anyway). Harder to tune, but worth it.
Regarding compressors, add one to Barry's comments - oiled compressors usually cost considerably more, initially. I've gone through 3 oiless compressors in the past 10 years, finally dumped the green on an oiled compressor, vertical of course. Do the math. Same with guns. Barry's Binks was probably more than a few dollars more the the DeVilbiss. In the end, you get what you pay for.
Build instruments. Sell instruments. Buy equipment. In the end, the one with the best tools, WINS! Argh argh argh argh!
Yeah, I forgot about longevity. Oil-lubed compressors last a wee bit longer. I have had my Speedair for over 25 years and have not had to rebuild it yet. Admittedly, my use of it is a little bit sporadic, but still...
In the end, the one with the best tools, WINS!
Actually the first one to his/her estate sale usually wins...