LVLP/HVLP compressor

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  • LVLP/HVLP compressor

    Hi all, i'm new here.
    I've had little experience in finishing and the experience wasn't too impressive maybe because I never had enough time to learn about the different finishes and their interaction.

    Now that I have more time for woodwork and am interested in working on a number of projects in the house (cupboards, tables etc.) as well other smaller /artistic pieces, I would like to purchase some equipment to make the finishing faster , more enjoyable and of a higher quality.


    After looking around on the web, I thought a LVLP/HVLP compressor https://mechanicfaq.com/air-compressors-for-hvlp/ setup and spraying water based would give me as little mess as possible in the garage, a compressor (which I don't have) and possibility of the infrequent finishing of anything I end up welding.


    I have listed a couple of spray guns below. Could someone comment on
    - whether any of the guns are OK/ overkill (I listed the gravity feed/can't say whether that's the best option),
    - what nozzle size I should go for if I was getting one gun (nozzle replacement price = cca 30% of nozzle+gun). I have no experience whether changing nozzles/cleaning one gun makes sense.
    - would two guns be more appropriate (eg one good one and one cheaper one I could use for finishing welded items) / which nozzles ?
    - what compressor size should I go for not sure how to work it out? (I understand pressure* volume = constant , so 100l at 10psi (compressor pressure) looks like 400l at 2,5psi(at gun) but not sure what compressor capacity should be I'm not going to be hurrying to do any work, but I don't want to get an undersized compressor.

    Optima 900 LVLP
    Nozzle sizes 0,8 - 3,0 mm Recommended pressure 2,4 3,0 bar
    Using nozzle 1,5mm
    Round jet: 2,5 bar ( 35 PSI =8cbm/h) = 111,0 l / min
    Flat jet: 2,5 bar ( 35 PSI = 17cbm/h ) = = 237,0 l / min

    Optima 650i,
    nozzles sizes:0,5 - 3,0 mm
    Air consumption nozzle size of 1,4 mm.
    Round jet:
    2,0 bar (28 PSI) =5,7 cbm/h = 96,0 l/min 2,5 bar(35 PSI)=6,7 cbm /h=113,0 l / min
    Flat jet:
    2,0 bar (28 PSI) =11,5 cbm/h=193,0 l/min 2,5 bar (35 PSI) =13,6 cbm/h = 228,0 l / min

    SATAjet 3000 HVLP, SATAminijetģ 4 HVLP SATAjetģ K3HVLP
    also Devilbiss and Binks
    Some Cheaper guns:
    Kestrel 2004H LVLP (cheapie) needle 1-2,5mm
    K-887M (prowin tools Taiwan) needle 1-2,5mm
    Last edited by Fleri; 12-14-2018, 08:07 AM.

  • #2
    I use a Binks siphon gun, I think itís 5 cfm @ 50 psi, for my metal painting. Outside use only because itís overspray goes everywhere. It will also work a compressor to death. My compressor is a 15 yr old 5 hp electric Ingersol Rand, not sure of the cfm, on a 60 gallon tank. Its blown the head gaskets on it several times during large paint jobs, so obviously it isnít large enough for the job. I use a couple of cheapie hvlp gravity guns for heavier paints with some success, I would never recommend or consider spraying paint in my shop or garage with anything but a occasional squirt with a rattle can.
    To answer you question, like I recommend for band saws, buy as large of a compressor as you can afford or fit in you shop. You can always regulate acompressed air down but you canít regulate it up. Plus, with a decent size compressor you can also operate impact wrenches, grinders and muffler guns.

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    • #3
      For HVLP paint spraying a dedicated high volume turbine style air source probably makes more sense. HVLP needs a lot of airflow (high CFM). Using a conventional air compressor - high PSI but low CFM - and regulating that down to the low HVLP pressure levels doesn't give as much CFMs as you'd expect unless you also swap hoses. Normal air compressor hoses are fairly small in diameter while HVLP hoses are much larger. Trying to shove high CFM through a smaller diameter hose just creates a lot of losses (friction) which a) reduces the CFM at the paint sprayer and b) as you cycle the sprayer trigger on/off/on/off over and over those losses will bounce up and down so you won't have a very consistent pressure right at the sprayer.

      Not long ago I bought the Earlex HV5500 Spray Station (the one with the blue plastic bottom and tall handle). For woodworking finishes, polyurethanes, etc. it has been quite good. The gun that Earlex includes is easy to clean, easy to use, and the spray pattern is easily and quickly varied from a vertical fan, to a spot, to a horizontal fan. It really is easy to use and works well. It often goes on sale with a deal for extra tips & needles: smaller and larger needles for different thickness/viscosity materials. So far I've used the "stock" one for all of my woodworking tasks.

      What tasks do you envision for a compressor with your welding? Running an air grinder? Sandblasting? More painting? I haven't tried heavy latex paints in my Earlex so I don't know how well it'd do with those... or if they'd have to be thinned considerably to work well. My gut feeling though is, with the larger diameter needle in my collection, the Earlex probably would work fine with only minor thinning. I have a conventional 2HP oiled compressor (90psi @ 6 CFM) for "car shop" work - air tools, grinders, etc. For painting, I had a lot more trouble using it than I've ever had with the Spray Station though that could be due to a) less experience on my part when I was using the compressor for painting, and b) lesser quality spray guns compared to the Earlex gun. 90psi at 6CFM seems to be a "sweet spot" for home air compressors; that'll run most tools other than high volume things like sanders or larger sand blasters. One thing about typical high-psi air compressors: they are not designed for more than about a 50% duty cycle - i.e. the motor should be running less than half the time. If the motor is running constantly most units will overheat or suffer reductions in lifetime. Trying to use such a compressor for HVLP work often leads to well over 50% duty cycle... while turbine based compressors designed for HVLP happily run for hours on end.

      I don't have much experience with different spray gun brands. My HF guns respect the "you get what you pay for" motto. My Sears Craftsman gun (made by who?) coupled to my 2HP compressor was never that impressive either. The Earlex 5500's stock gun beats all of them by a mile.

      My recommendation: browse a few wookworker finishing books first. Bob Flexner's books are very detailed and include a lot of discussion on what finishes work well together and what types don't play nice together. He also goes into a lot of the (often incorrect or misleading) terminology used by finish manufacturers - e.g. some sell products with "tung oil" in the name that have no real tung oil in them. There are a few other authors out there too. I've had good luck with plain old pre-mixed shellac (my most commonly used is Zinsser's Seal Coat which is sold as a sanding sealer but is basically a diluted shellac), brush-on and spray-on polyurethanes, and gel stains. Some of Flexner's stuff may be overwhelming - you may come away afraid you'll never be able to remember what combinations do work and what ones don't work - or that you can't trust the labels on any manufacturer's packaging... what I ended up concluding is that products sold by one manufacturer typically do play nice with whatever other products from that same manufacturer are listed on the label. So see what products are available in your local stores and see what Flexner has to say about them... that'll help you decide if that brand is worthwhile or is just trying to get you to buy a ten-step finishing process for no good reason. Besides Zinsser, I've had good luck with Minwax gel stains and polyurethanes which are readily available. I wouldn't be surprised if you find that a dedicated HVLP unit for woodworking meets your needs and that modern cordless tools can replace a lot of the "metal shop" air tools of yesterday. I can't remember the last time I reached for my 2HP compressor + air driven impact hammer... my Ryobi cordless impact tool (1/2 inch chuck) and my newer Ridgid work just as well, are quieter, and quicker to get set up. I use a corded cut-off grinder with a grinding wheel to grind/flatten welds rather than a air powered tool. So my 2HP 90 psi compressor mostly does tire inflation duties these days... I have an air powered metal cutting saw but I haven't used it in ages either.

      mpc
      Last edited by mpc; 12-14-2018, 10:27 PM.

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