Problems Spraying Waterborne Finish With My New Fuji

[Jim Tabor]

I bought a Fuji Mini-Mite 5 with a T75 gravity cup last December and I’m having a difficult time getting the adjustments correct.
I’m using waterborne General Finishes Enduro-Var and Crystalac Top Coat Poly thinned up to 20%. After talking to Fuji tech support a couple of times and continually being told I’m using the wrong needle/cap set and not thinning the finish enough, I said to heck with it and bought everything from 1.0 to 2.5. I started the 1.0 needle, than a 1.3, 1.5, 1.8 and finely a 2.0 to get it to spray with any satisfaction (I haven’t tried the 2.5 yet). Makes me wonder why this gun comes with a 1.3 if a 1.8 or 2.0 is needed for waterborne. Anyway....can anyone tell me what I maybe doing wrong (seems to be a heck of a learning curve with this thing) and has anyone else had similar problems spraying waterborne finishes with a Fuji? I now have about $1300 in this Fuji and my old $249 Earlex 5500 seems todo a better job with the same needle I used for oil base poly.

[John TenEyck]

I don't have a Fuji but a friend of mine does. You didn't say what problems you are having and that would be big help in offering specific recommendations, but when my friend sprays EnduroVar and similar WB products he has a tough time avoiding a rough surface finish. His Fuji runs at around 8 psi, including the cup, so there's no need to thin it to spray through a 1.3 mm N/N. I think the problem he has is related to the finish drying too quickly because of the heated air from the turbine. I spray with a pressurized HVLP conversion gun and have no trouble laying down a uniform finish with a 1.0 mm N/N with no gritty feel.

If this is the problem you are having I would add 5 - 6% of GF's Extender (with no other thinning) and try the 1.3 mm N/N again. Extender will retard the drying so that it gets to the surface of the wood and has time to flow out before setting up. You could possible get by w/o Extender by holding the gun closer to the work and/or slowing your pace but Extender works great with no negative other than it's another, though minimal, cost.

If you are having some other problem, please let us know.

John

[Jim Tabor]

The problem is that I can't get anything out of the gun if I use less than a 1.5 needle and then it's just a mist. By going to a 1.8, thinning like 20% and opening the fluid control 3-4 turns I can get a pretty good coverage. The Fuji Mini-mite 5 is rated at 9.5 psi. so this just doesn't make sense to me. Fuji tech support is telling me I should be using at least a 1.8 needle. plus the thinning.
I would like to hear from other Fuji owners that spray waterborne on how they have their gun set-up. Thanks

[Wayne Lomman]

If your gun works with a 2.0 tip, then use it. Tip choices are available so you can use what works best. I rarely use anything finer than 1.8 and there are plenty of examples to show it works. What you have to do is learn how your gun reacts to changes in tip size, air temp, fluid viscosity and the range of gun adjustments. Time and practice will fix this. Cheers

[John TenEyck]

OK, I read your original post again and see that you have a gravity feed cup on your gun. For EnduroVar (about 45 seconds #4 Ford cup) you should be able to use a 1.8 mm orifice w/o thinning. The fact that you are having to open the fluid control 3+ turns, after thinning it 20% suggests something is wrong. I use a 1.8 mm on my gravity feed gun w/o thinning and only have to open the fluid control about 2 turns. Are you sure there's nothing plugging up the gun internals? Does the gun have an internal filter? If so, remove it and just filter the finish when you pour it into the cup - which you should do anyway.

Go to the 2.0 mm orifice rather than thin a WB finish. That is a move you make when you don't have a larger orifice.

Buy a cheap #4 Ford cup and measure the viscosity of your finishes. EnduroVar should be around 45 seconds. I measure GF's High Performance Poly at 60 seconds, and to spray that well through my 1.8 mm gravity feed gun I have to thin it 6% with water to get it down to 45 seconds. But that's only 6%, no where close to 20%. That's how much I would guess you might add to EnduroVar to spray it through a 1.0 or 1.2 mm orifice gravity gun.

John

[Jim Becker]

And to add to John's comments, you really never want to thin a water borne finish more than 10%, if at all. Water is just the "carrier"; it's not the solvent. So by over-thinning, you're spreading out the finish molecules a lot farther than desired to obtain a good finish coat once the water flashes off and the finish cures.

[Jim Tabor]

John,
Thanks for the feedback. I really think there is something wrong with my gun. I'm am using a #4 Ford cup and I have to thin so that the material flows through the cup in about 18-20 seconds. I said above that I had to go to a 1.8 mm needle but actually I went to a 2.0 mm needle to get it to put down a smooth coat and as Jim said I'm probably over thinning. I feel the advice I've received from Fuji tech support doesn't make sense and it may be they just don't understand my problem.
I'm not sure how far I can disassemble the gun myself and if there is something wrong I probably wouldn't recognize it. I was hoping some T75 gravity gun owners would give me some information on how their gun is set-up to spray waterborne poly before I send mine to Fuji to have it checked.

[John TenEyck]

Jim, you should be able to spray a finish with a viscosity of 45 seconds with no problem through a gravity feed gun with a 1.8 mm orifice. The fact that you are still having trouble with the viscosity all the way down to 20 seconds and with a 2.0 mm orifice pretty much confirms that something is amiss with that gun. Could there be something wrong with the air flow? I know nothing much about turbine guns so excuse the question if it's stupid. But if you are confident the air system is performing properly then it has to be something in the gun that shouldn't be. If so, I'd send it back if it's still under warranty. If it's not, I'd tear it apart to find out what it is. Guns are pretty simple so don't be intimidated. Take the cup off. If there's a filter below it pull it out, throw it away, put the cup back on and try spraying again. If there is no filter below the cup, then remove the needle next, followed by the nozzle. That's as far as you should have to go to find any obstruction, foreign debris, etc.

The feedback you've been getting from Fuji makes me wonder about their competence.

John

PS: Have you checked the vent on the top of the cup to be sure it's open to air? If that vent is plugged finish won't flow into the gun as it should.

[Jim Tabor]

I'm going to send the gun to Fuji since it's only two months old and let them check it out. It seems when I contact them I get conflicting information.

[Jamie Buxton]

I spray with a Fuji gun and an Accuspray turbine. I routinely spray waterborne lacquer (usually General Finishes Enduro Clear Poly) without thinning -- just use what comes out of the can.
My gun is an XPC, which looks like yours with a smaller, aluminum, cup. I think your gun should behave like mine.

One thought is that the cup is supposed to be pressurized by a flexible tube running up from the body of the gun. Is yours connected like that? If you disconnect the tube at the cup, and run the turbine, can you feel air coming out of the tube? On mine, there's a check valve inline in that tube. Is it there? Is it stuck? Is it installed backwards? A different failure might be the the cup lid is not sealing tightly to the cup. Are you missing the gasket?

[Jim Tabor]

Thanks Jamie,
You solved my problem. I connected the turbine, removed the cap and found out the tube check valve was defective, wouldn't let air pass in either direction. I Replaced the check valve, installed a 1.3 needle/air cap put in some un-thinned waterborne poly, did a test spray and everything worked as it should. I should have been able to find such a simple problem on my own. I'll know next time. Jim

[John TenEyck]

Thanks Jamie,
You solved my problem. I connected the turbine, removed the cap and found out the tube check valve was defective, wouldn't let air pass in either direction. I Replaced the check valve, installed a 1.3 needle/air cap put in some un-thinned waterborne poly, did a test spray and everything worked as it should. I should have been able to find such a simple problem on my own. I'll know next time. Jim

Hmm, so it's not a gravity feed gun after all. My friend had one of those check valves fail on his Fuji. I finally convinced him to go with the 3M PPS cup system which allows you to spray at any angle. Part of changing to the PPS system is removing that check valve. One less thing to fail; always a good thing.

Glad you figured it out. And I still wonder about the competence of Fuji.

John