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Thread: Another HVLP conversion gun?

  1. #1
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    Another HVLP conversion gun?

    I have a Fuji MPX 30 I bought recently and generally like, although I wish there was a little more adjustment for fan size. I also have a Wagner 1 qt conversion gun setup which seems to work fine, but with the 1 quart can is a little bulky. I'd like to get another gun somewhere in between the $350 cost of the Fuji and the $15 Harbor Freight purple gun. I run the guns off filtered and dried normal shop air, don't want to get a turbine, and generally shoot WB finishes and shellac.

    Thanks

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    Quote Originally Posted by Dave Cav View Post
    I have a Fuji MPX 30 I bought recently and generally like, although I wish there was a little more adjustment for fan size. I also have a Wagner 1 qt conversion gun setup which seems to work fine, but with the 1 quart can is a little bulky. I'd like to get another gun somewhere in between the $350 cost of the Fuji and the $15 Harbor Freight purple gun. I run the guns off filtered and dried normal shop air, don't want to get a turbine, and generally shoot WB finishes and shellac.

    Thanks
    When you say you wish there were more adjustment you mean on the low/narrow side, right? The MPX-30 can atomize basically anything and outputs a lot of finish. It consumes a lot of air and isn't so good for pinpoint work (though it can do a credible job with the pressure turned down and a small N/N), so I'm guessing that what you want is more of a detail gun?

    I had a similar situation recently and got a QualSpray 5008. Unfortunately Homestead doesn't sell the bare gun, and the kitted versions with multiple nozzles/caps are almost as much as the (bare) Fuji.

  3. #3
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    What is it you want to spray? FWIW, the HF purple gun sprays shellac, dyes, and other low viscosity materials really well.

    John

  4. #4
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    By more adjustment on the Fuji gun, I mean the fan knob on the side. It's about a half turn from round pattern to full fan. On the $16 HF gun you get about two turns so it's a bit easier to tune the fan size.

    Yes, I have an older HF purple gun and it's worked surprisingly well for it's price, but I get an occasional drip from it which can cause a problem in the wrong place.

    I am mostly shooting furniture and furniture parts, using anything from sealcoat shellac to WB lacquer (Target 6000) and I'm trying out some GF Topcoat to compare to the Target, too.

  5. #5
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    Quote Originally Posted by Dave Cav View Post
    By more adjustment on the Fuji gun, I mean the fan knob on the side. It's about a half turn from round pattern to full fan. On the $16 HF gun you get about two turns so it's a bit easier to tune the fan size.
    Interesting, I actually consider that to be more of a feature than a liability, because it makes it easier to tweak the fan during spraying, without breaking stride to futz with an end-knob. I find that I can dial in what I want pretty precisely. It's a good thing that there are many options to accommodate different preferences.

  6. #6
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    The HF gun shouldn't drip. Buy another. As you know, it sprays shellac and other low viscosity products great. If you put a 3M pressurized PPS cup on it it will spray anything up to BM Advance really well.

    John

  7. #7
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    How do you put a pressurized cup on a gravity feed gun?

  8. #8
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    Quote Originally Posted by Dave Cav View Post
    How do you put a pressurized cup on a gravity feed gun?
    Like so:

    IMG-1466.jpg

    The regulator on the gun is a standard pressure regulator, which downconverts my 90 psi clean air supply to whatever the gun needs. The second regulator on the far end of the whip hose is a diverting regulator that passes the input through to the output unregulated, and diverts a 0-10 psi (settable) regulated feed into the Tygon tube that attaches to the cup.

    Note that because the cup regulator is on quick-connect fittings it can easily be moved from gun to gun (and all of my conversion guns have similar-length whip hoses to enable exactly that). Note also that because the quick-connect fittings are on the input side of the gun's input regulator I don't have to worry about pressure drops. It doesn't really matter if the gun's input regulator sees 90 or 85 psi...

    EDIT: IIRC John's setup for his QualSpray 6008 is the reverse of mine: He has the diverting regulator on the gun input, and the gun input regulator on the other end of the lead-in hose. The advantage of that is that he doesn't have to deal with the hassle of a long Tygon tube since the cup tap-off happens about a foot from the cup's air port. He can probably use the stock tube that comes with the H/O PPS cup. The disadvantages are that the gun pressure isn't as well-regulated (since the whip hose and diversion losses are both on the output side of the gun regulator), it's a little more hassle to adjust the gun pressure, and the diverting regulator isn't as portable to other guns.

    One important thing to realize is that the cup pressurization feed only needs enough cfm to displace finish as it is sprayed. A cubic foot is about 8 gallons, and my fastest gun takes minutes to empty a one-quart cup, so less than 0.01 cfm. That's why I can get away with using a long 1/8" ID Tygon tube from the diverting regulator.
    Last edited by Patrick Chase; 05-17-2018 at 5:45 PM.

  9. #9
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    Thanks, Patrick. Since I still haven't even looked into using the disposable cup systems on any of my guns, that's a little advanced for me.

    Speaking of which, can anyone recommend a generic, inexpensive, readily available disposable gravity cup system?

  10. #10
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    Quote Originally Posted by Dave Cav View Post
    Thanks, Patrick. Since I still haven't even looked into using the disposable cup systems on any of my guns, that's a little advanced for me.

    Speaking of which, can anyone recommend a generic, inexpensive, readily available disposable gravity cup system?
    If you want "readily available", and particularly if you don't want to be locked into a specific maker's guns, then 3M PPS is the only way to go. Some spray gun makers like SATA, Graco and DeVilbiss make competing systems (RPS, FlexLiner, and DeKups, respectively) but they aren't as widely available, don't support such a wide range of guns, and are at best 10-20% cheaper.

    Cup plus liner cost for PPS is about $1.75 per use for 8 oz "mini" cups ($87 for 50 liners + lids) and about $2.75 per use for 32 oz "large" cups ($66 for 25 liners + lids). IMO that's reasonable relative to the time, hassle, and solvents you save by using them, but different people will have different sensitivities. PPS cups and lids can be reused if desired, particularly if you remove the built-in filter and pre-strain the finishes.

    Also I don't know of any other system with an equivalent to the pressurized PPS H/O cups, like the one that I pictured a couple posts back. They're expensive to start ($40 for the small cup and $70 for the large) but not horribly so when you consider that the large cup has to safely withstand ~250 lbs (10 psi times ~25 square inch cross-section). As John said, pressurization is a big win for spraying heavy finishes from smaller guns (or for fine work with larger guns), because it enables you to push higher-viscosity finishes through smaller nozzles, which in turn enables low-airflow guns to effectively atomize those finishes. The unpressurized cups are much cheaper. Even if you use H/O cups it's useful to have a couple of the cheap ones on hand to store half-filled liners between jobs. For example I often keep a 32 oz liner with 2 lb dewaxed platina shellac (or SealCoat) on hand, usually with all excess air squeezed out.
    Last edited by Patrick Chase; 05-17-2018 at 11:15 PM.

  11. #11
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    I've been using the same 5 large PPS liners and lids that came with my gun for 3 years now, and have sprayed many, many gallons of finishes. They clean out easily and the filter in the lid cleans out, too, as long as you don't let finish dry on it. The PPS system is marketed as a disposable system, and it is if you want to use it that way, but it doesn't have to be. Also, keep in mind that all PPS systems allow you to spray at any angle, including upside down. This greatly expands the capability of a gravity feed gun. And the H/O cup allows you to spray an incredibly wide range of finishes with a gun that otherwise has limited range. IMHO, it's a cheap investment.

    When I first got my PPS equipped gun I had both a mini gun regulator and cup regulator attached to the bottom of the gun:

    IMG_4331.JPG

    It sprayed fine but it was immediately obvious this made the gun difficult to handle. So I installed a larger regulator 20 feet upstream and now just have the cup regulator (and in-line filter) on the bottom of the gun.

    IMG_5010.JPG

    There's no trouble adjusting the gun pressure with this arrangement. I stand at the regulator, pull the trigger on the gun, and adjust the regulator to whatever I want. You only pull the trigger back partially, not enough to start finish flow to the gun, so you can adjust it before or during a spray session w/o issue.

    I guess you could combine what Patrick and I both do and put both regulators upstream. That would make the gun as small as possible, which has advantages when reaching into cabinets, between face frame openings, etc.

    John

  12. #12
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    Quote Originally Posted by John TenEyck View Post
    I've been using the same 5 large PPS liners and lids that came with my gun for 3 years now, and have sprayed many, many gallons of finishes. They clean out easily and the filter in the lid cleans out, too, as long as you don't let finish dry on it.
    Absolutely. The reason I think that it's a little easier with the filter removed is because that makes it easier to store finish in the cup or to add additional finish (or tints, or whatever) to an "already-wet" cup without removing the lid. If you're going to clean the cup out then it doesn't really matter as long as you avoid letting finish dry on the filter, as you say.

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