Looking into HVLP - air compressor requirements?

Discussion in 'Finely Finished' started by jsnwhite619, Dec 11, 2019.

  1. jsnwhite619

    jsnwhite619 Friend of Leo's

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    I don't build guitars, but I build amp & speaker cabinets, along with other woodworking projects. I've used wipe-on polyurethane up to this point, but I've been looking into lacquer & spraying lately. For starters, what size air compressor would I be looking at to spray a cabinet? CFM requirements, PSI, etc?
     
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  2. Skydog1010

    Skydog1010 Tele-Afflicted Platinum Supporter

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    how large are your projects?
    what are your space limitations?
    booth shooting?
    Just going to use it for shooting lacquer? many folks find like a zillion other things they can use pneumatic tools for!
    what's your budget?
    want a compressor that clears it self when shut off?
    where are you located (humidity)?

    I only use German made guns
    I use a 30 gallon 120psi compressor from craftsman
    I have to purge it after every use.
    If your are thinking a hobby sized compressor, then you best be only shooting one side of a guitar at a time, in your case, I would not get a small bedroom hobby compressor, I have one for clean up and that's all it good for. will blow steady for about 30-40 seconds max on lower pressure setting
     
  3. telepraise

    telepraise Tele-Holic

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    Depends on the gun. I started with a Devilbis Finishline. I wanted 11CFM at full pressure. Have since moved up to a LVLP gun from Homestead Finishing, less air hungry and better performance. I use a 60 gallon (220v) compressor and it still cycles a few times on bigger spray jobs involving several cabs or doors. PSI won't be an issue, any compressor is going to carry the load at 120+ PSI. Sufficient CFM is going to be the limiting factor. That means bigger compressor and tank. You're probably going to be looking at a 220v rig for the capacity you want.

    Skydog raises some good questions. I live in Florida which means I do finishing year-round but have to bleed the water off the bottom of the tank every session. Also consider what you're going to be shooting. Nitro is way too delicate for cabinets. You're more likely to be applying a urethane or catalyzed varnish. If you think you'll end up shooting adhesive, make sure the gun you get has large enough tip sizes available for it.
     
  4. jsnwhite619

    jsnwhite619 Friend of Leo's

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    Yall have definitely given me more to think about in terms of size requirements & startup cost. I watched some youtube videos last weekend of guys using it for furniture projects, and using pre-cat lacquer. The turn around time is ridiculously fast in comparison to oil based poly.

    I was hoping for a 30 gallon vertical tank for a smaller footprint in my shop. Most of my builds are Pro Jr to 5e3 sized cabinets.
     
  5. old wrench

    old wrench Tele-Afflicted

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    The smaller the tank, the closer ya need to have the compressor's output match your guns requirement if you want to spray without interruptions.

    Here in the U.S. compressors are usually rated by cfm. output at 40 or 90 psi.

    For a true HVLP gun I'd think you'll want a compressor capable of putting out 12 - 15 cfm. at 40 psi. - if you want to spray without interruption. Lot's of air :).

    If I was buying new HVLP equipment, I think I'd check out the package setups, which come with a gun and a turbine type compressor that are matched up, performance-wise.


    Take what I say with a grain of salt; I know a bit about compressors, but I'm no authority on HVLP systems. I use a cheap "conversion" gun and a moderate sized compressor. My spraying needs and expectations (and bank account ;)) are limited, so I can get by using a spray system that has performance limitations and still be satisfied with the outcome.



    g
     
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  6. Vizcaster

    Vizcaster Poster Extraordinaire

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    If i had it to do all over again, I would indeed have gone your route by purchasing a huge compressor (possibly second hand) in order to get the flexibility of so many different spray gun offerings. HVLP 'conversion' guns that run off of regular compressors have to some degree been supplanted by "HTE" or high transfer efficiency guns at the higher end of the market. Industrial users and autobody shops still have compressor lines.

    Having said that, i'm very happy with turbine-driven HVLP kits especially for furniture. I can do small jobs inside in the shop (with ventilation) and major furniture assemblies outside in the garage. If you're doing cabinetry, there may be some need for on-site finishing (e.g. to clearcoat over a set of bookshelves that the house painters did along with the trim). So the portability of an HVLP turbine can be a great advantage.

    For every step up in quality and cost, you see fewer plastic parts and more adjustments available (for instance the ability to move the air-cap forward and back to change how flat the fan gets). I started with a Campbell Hausfeld, and graduated almost immediately to a Capspray (Wagner). Now I have a Canadian made Fujispray turbine and gun with a 3M disposable liner cup system and it beats everything in terms of reliable consistent atomization and control of the spray fan. Expensive but probably along the same order of magnitude as a good large compressor and a few spray guns. i believe Homestead Finishing and Gleem Paint are still in business they both have a good assortment of equipment options.
     
  7. Nickfl

    Nickfl Tele-Afflicted

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    I've used the $10 harbor freight conversion gun and even a cheap gun like that can work well, but as others said you need a serious compressor for a conversion gun to work well. Using the little 2.5 gal compressor i have at home it'll spray for maybe 20 seconds at a time and even then it doesn't even really work well except for small stuff. I've used it with the 80 gallon, 220v belt driven compressor I have at work and it works shockingly well for a cheap spray gun but that is a $1500 compressor... And ideally you need to be setup so that your air is dry and cooled for spraying as well as having sufficient CFM.

    I'm hoping I'll be getting a hvlp turbine system for Christmas. It seems like that is a better solution for home use unless you are likely to use some major air tools in you shop as well.
     
  8. vid1900

    vid1900 Tele-Meister

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    Every gun tends to under rate how much air it really needs.

    Every compressor tends to over rate how much air it can deliver.

    So if you are even **close** to ether's minimum, you'll be waiting for the tank to recharge.
     
  9. vid1900

    vid1900 Tele-Meister

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    Make sure that any compressor you buy has an iron head, and that you can still get valves for it.

    Just search Google for valves for the model. If they don't sell replacement valves, don't buy it!

    If you are buying a used compressor, download the manual and see how long it takes to bring the tank up to 120psi

    Now time how long it takes with the used compressor. If it takes 30% longer than the math says it should, it needs the valves rebuilt.

    Look on CL for a solid old school USA compressor like a Saylor Beall. It's not a name that most people recognize, so often they go cheap. You can still get all the parts to keep them running, and it will outlive you and the next few owners.
     
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  10. Informal

    Informal Tele-Holic

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    Don't overlook the Harbor Freight HVLP's

    I have over $1500 invested in 2 different Binks guns, that are admittedly...very old now.

    I bought a HF gravity feed model, to shoot a nasty 2 part primer (think sprayable Bondo) it takes a ton of solvent to clean, So I figured if nothing else, they were so cheap.. I would try it out...And just toss it.

    It performed so well, I actually cleaned that bastard out!

    It shoots every bit as well as my two aged Binks guns.

    This is my last Jet Ski project... Shot the primer, color coats and clear coats using the HF gun.

    Superfreak.jpg
     
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  11. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

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    None.

    Buy an HVLP turbine/hose and gun integrated system. A good HVLP gun that can be adapted to an air compressor will cost almost as mush as an entire HVLP rig - and you'll still need a huge compressor.

    A true HVLP runs at 4-10 PSI and requires around 26-30CFM of air. That type of system meets air quality requirements and gives you superb control, with an extremely high transfer ratio and very little overspray that you can generally sweep up. Masking is minimized.

    You should absolutely avoid "bleeder" systems that hav the air running all the time - the air should be triggered with the material. A decent compact HVLP rig can be purchased for $300-500, including the required 1.0mm lacquer air cap/needle set.
     
  12. Peegoo

    Peegoo Tele-Afflicted

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    Yeah. Air compressor ratings are total BS. Everybody does it, and here's why.

    Air compressor makers and distributors accurately spec their CFM @ [PSI] ratings based on flow and tank pressure at the *inlet* of the compressor--not the outlet, where you're standing with your tool in your hand.

    Consumers buy compressors based on tool demand. The problem is that most compressors for home gamers are sadly underrated for even the simplest of air-powered tools. Most compressors deliver to the outlet only about 25% of their advertised flow.

    This is the reason why you see six-foot-tall compressor tanks with 5HP (and larger) motors driving multi-cylinder compressors in industry and even small professional shops. These are equipped by people that know how the game is played.

    In order to match a compressor with the tool(s) you'll be running, you must take the maker's numbers, divide them by 4, and expect to see that at the outlet...and go from there.

    Here's a pretty good explanation of this subterfuge:

    WARNING: do not click on the play button if you're offended by salty language inappropriate for children:

     
    Last edited: Dec 18, 2019
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  13. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

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    The best layman's-term language description of WHY almost all home compressors won't spray at HVLP pressures successfully.

    Many buy cheapo Harbor Freight "HVLP" labeled guns, hook them up to a conventional rig, dial the pressure up to 60-90PSI and figure they have an HVLP rig. Because of the stamp on the gun.

    Not even *close*. That's simply a cheap conventional spray rig - the same type that's been in commercial use since the 1920's.

    HVLP is a *specification* governing output (NOT input) pressure and transfer efficiency - NOT a marking on some piece of equipment. And for commercial work in some areas it is also a legal requirement.

    Again, HVLP means 4-10 PSI with whatever CFM will give you a good fan pattern, precision control, transfer efficiency (what you spray sticks to the surface - doesn't bounce or end up as overspray) in the (usually) 80-90% range and provides the advantages of little cleanup and very little masking.

    There are two ways to get there - 1) an HVLP turbine with large air hose and cup or gravity gun (essentially a reworked vacuum cleaner woking in reverse, with heated air), or a (usually) hard-wired, permanent mount or large cart-mount compressor, pressure pot or cup, and fairly expensive HVLP gun adaptable to a compressor system (decent ones run $250-500 - just for the gun. Air cap and needle for lacquer is usually extra, as are pot, cup, high pressure hoses and heavy duty, high-output industrial compressor.).

    A pancake compressor and $19 "HVLP gun" won't cut it. It won't even work as a conventional spray rig.
     
  14. sleazy pot pie

    sleazy pot pie Tele-Afflicted Silver Supporter

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    If you don’t need the compressor for anything else, check out the earlier 5500
    It is an all in one for about $300 +\-
    It is more than enough for what you are doing
     
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  15. Dick Hutchings

    Dick Hutchings TDPRI Member

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    I'm saving my pennies for this instead of a compressor. I think I want this,
    Fuji Mini-Mite 3 T70 HVLP Spray System
     
  16. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

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    Now THAT is a true HVLP system. A high quality compact portable. There are also less expensive units that are good - the main thing is to avoid "bleeder" systems, guns alone (which do NOT mean HBLP, only that they can be used that way) an single-unit "buzz bombs similar to old Wagner "Powerpainter" that claim to be HVLP.

    REAL HVLP systems include either:

    1) a "turbine" with a 1" or so diameter, low pressure hose - that work and sound like a reverse vacuum cleaner (seriously) and a compatible gun (they are NOT universal) that triggers material and air at the same time and has interchangeable "needle and air cap" sets with different orifices for different viscosity (thickness) materials, or

    2) an industrial air compressor capable of maintaining 4-10 psi air pressure - AT THE TIP - with around 26cfm of air minimum (and maintain a controllable, adjustable fan), a special pressure pot with dual HVLP hoses (for air and materials - not the big hose used with the turbine) or integrated cup at the gun, with the gun an HVLP-only unit with interchangeable needle and air caps (same as above).

    Average quality guns for type 2 run around $250 -300, and each needle/cap set $75-150. A goo pressure pot costs about the same as a gun - so unless you already have a stationary or cart-mounted, large industrial compressor it's usually not worth trying to build a type 2 rig. They'll usually exceed the cost of a complete high-output turbine rig (with gun, hose, accessories and several needle/cap sets)

    IMO a turbine system is a better buy. Generally less expensive, smaller, easier to store and clean, less expensive - and generally better suited for spraying lacquers. The big compressor rig systems are engineered more for fixed in place shop coating systems with a commercial/industrial spray booth as well.
     
  17. rolandson

    rolandson Tele-Holic Silver Supporter

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    I've a 2.5 gallon compressor attached to a 10 gallon aux tank serving a gravity gun. It works well. But I only use it when I've a lot of spraying to do. Something like a single guitar body / single 12 or 2-10 cabinet, and I'll just use rattle cans.
     
  18. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

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    Gallons mean nothing. What BHP? What HVLP gun are you using, and how are you measuring pressure at the tip? Measuring the CFM? Is it a bleeder or non-bleeder? What kind of hoses are you running?

    If you are not running 4-10psi and +/- 26CFM at the orifice - constant - you're not spraying HVLP no matter what gun you are using.

    My educated guess is that you are doing conventional medium to high pressure spraying , losing about 50-70% of the material to bounce and overspray. The results may look good but it defeats all the advantages of HVLP - fan control, limited masking, almost no overspray or bounce, +/- 90% transfer efficiency and quicker dry time/smoother coats due to material heating.
     
  19. rolandson

    rolandson Tele-Holic Silver Supporter

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    All of this deduced from the capacity of my compressor/auxiliary tank and type of gun I use! And here all I intended was to answer a couple of basic questions posed by the OP.

    I don't measure pressure at the tip. I look at what the spray is doing and adjust until I like what I see. I use an air hose I bought at a hardware store and a gun purchased a a paint store. I don't give a rat's ass about lost material. My only interest is the quality of the result. If it's what I want, I'm happy. If I put more lacquer on my shoes than on the target...who cares.

    But clearly a master has the floor. I defer to the expert...

    cornfield.
     
    Last edited: Dec 21, 2019
  20. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

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    I was describing the difference between HVLP and conventional spray, and your comment was lacking in detailed information that many would consider critically important.

    While lost material may not be a concern for you, it is for most inexperienced applicators as it increases cost; indicates excessive pressure; creates overspray, orange peel and material "bounce" and overall difficulty controlling the results.

    If you don't know your pressure at the tip with conventional spray how do you determine the necessary material viscosity? Those two have to balance to properly atomize the spray and do it without striping or "tails".

    Sure, you can guess your way through the process - but it wastes time and material when there are easily obtainable reference charts from any material or spray equipment supplier. Do you measure wet film thickness at the start to set a standard for the combination of material and spray equipment - and so you'll be able to calculate dry film thickness?

    One of the big advantages to HVLP is the high transfer efficiency - which goes along with precise material control. It also puts less "dry spray" in the air, which can land on freshly coated surfaces and cause roughness; reduces cleanup and masking; and reduces the total amount of solvents blowing around in the air and accompanying odor control issues. You also get far more consistent wet (and dry) film thickness. That may not make much difference in initial appearance - but wait 10 years.

    Those may not be problems for you - but they are for most applicators. Those are issues that might be worth considering when making equipment recommendations or even simply stating "it works for me".
     
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