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fish eyes are the biggest indication of moistuture or oil in the lines.
but fisheyes can also be caused by surface contamination.
but fisheyes can also be caused by surface contamination.
Compressor best practises and HVLP setup
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rharshberger
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Silicone based oils and lubricants are one of the best known for causing fisheyes alongside the moisture issue.
Simply put what it causes for me is a bunch of unnecessary sanding and re-coats. BTW Nathan I saw your newest paint job, very nice work! What model HVLP gun are you using?
Nathan
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Thanks, my HVLP gun is an inexpensive TPC Global brand spray gun that I bought several years ago. It seems to do a good job but it is the only paint gun that I have used so I don't have anything to compare it to. Now that I have been painting with a gun for several years I would be willing to buy a better one if I thought it would make any difference. I would also like to buy a separate one to use for primer.
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The Harbor Freight gun is perfect for a dedicated primer gun, and can be had for $10 on sale and/or with a coupon. That said, the TCP guns are a better value and offer parts availability.
BayouRat
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Is a good airbrush a good thing to buy? My friend paints all his rockets with an airbrush and they look awesome.
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Yes. You can get a good one for under $100 to as many $$$ as you would like to spend. That's a whole other thread, with opinions as strong as a Ford/Chevy/Dodge debate.
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the main difference between low priced guns and higher priced guns is atomization of the paint, which better atomization helps paint lay down smoother and more evenly.
i started with a devilbiss startingline set- base gun w/1.3 tip, primer w/1.8, and touchup gun with a 1.0 tip.i wasnt ever able to get of OP with it.
bought a copper tekna. MAJOR improvement. the atomization is awesome-paint almost looks like dust coming out of the tip and lays smooth as glass.
using the startingline helped me learn gun set up and control. made getting used to the tekna nice.
i also bought a HF purple gun a while ago,just to see what everyone was raving about. i used it once for base and clear on some motorcycle tins for a friend just wanting fresh paint on them. it sits on the shelf. i wont use it for anything other than thinned primer thats getting sanded.
theres some other very good gun brands out there. iwata,sharp, sata( if ya wanna spend mucho bucks) ,to name a few,and all make smaller detail guns that are very good,too.
Thanks for TPC tip, I just found some guns that are appropriate for my setup, mainly on the low volume side of HVLP guns.
I have come to the conclusion that I entered into the HVLP world with pure ignorance and a bit of luck. Naivety comes to mind, like most of this hobby. In my case I originally purchased a compressor, originally to run a vacuum generator for carbon fiber composite layups. After doing a couple of layups I figured there had to be better ways then running my compressor for 12 hours, so I built a vacuum system. Then I figured okay I have the compressor, which I was not using for anything, so why not try HVLP, it can pump 150PSI, so I naively hit the local Home Depot and picked up an HVLP gun. Not putting any thought into what the "H" in HVLP implies, that being volume of air.
The point being if anyone reading this can take away one thing when it comes to HVLP I would say make sure you match your gun with your compressor's ability to deliver air, including the hoses, connectors, etc.
Specific to TPC Global I just found these two guns which are perfect for my setup and reasonably priced.
https://www.tcpglobal.com/TCP-G6600-13_2.html?sc=120&category=2665716#.VzPhxGYhvIE 1.3 tip good for top coats
https://www.tcpglobal.com/TCP-G6600-18_2.html?sc=120&category=2665716#.VzPiHWYhvIE 1.8 tip perfect for a dedicated primer gun
Both of these guns are perfect for my compressor and my need for the following reasons:
- they are rated @ 4.7-7.1 CFM, this is considered low for HVLP and my compressor may do 5.5 CFM with my setup and working pressures at best
- they are gravity fed and I prefer gravity fed vs siphon based on limited experience working with both, in which I have gotten better results with the gravity plus the weight and balance of gravity fed just feels better in my hand so comfort and grip which is a factor for me
- they are both part of the 660 series guns and have interchangeable parts, tips etc.. This is a limitation for my current Porter Cable gun which has a 1.4 tip, great for base coats but no interchangeable parts.
- finally it has a nice big bowl that I can use with the Devillbiss DeKups system which I plan on getting down the road.
Knowing what I know now I would purchase a 2 stage compressor that can deliver more CFM and has a bigger tank, as the number of guns in the lower range is very limited. I would also settle on two guns, one dedicated for primers and the other for base and top or clear coats. In both cases the guns would have interchangeable tips and or accessories, which provides more options and more bang for the buck.
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Let the pressure off of the tank, drain any water, store it clean and dry.
I think that most of the stuff that youll read on HVLP guns is pretty much baseline for spraying large volumes of paint at one time across large areas like auto body applications. For rocketry, even large rockets, Ive found that you can do pretty good with far less than a full car paint booth. As long as your compressor/tank can maintain pressure and volume at the spray cap during your spray run, youre golden.
I used this compressor, which everyone said was too small :
https://www.sears.com/craftsman-3-g...p-00915362000P?prdNo=6&blockNo=6&blockType=G6
With this spray gun, which everyone said was total crap and not worth using as a boat anchor : https://www.harborfreight.com/air-tools/paint/20-oz-8-cfm-gravity-feed-spray-gun-67181.html
With these accessories, which everyone said was good money after bad :
https://www.harborfreight.com/air-tools/air-hoses/38-in-x-25-ft-pvc-air-hose-61977.html
https://www.harborfreight.com/Disposable-Inline-Moisture-Filter-68224.html
https://www.harborfreight.com/Inline-Desiccant-DryerFilter-68215.html
With this paint, which everyone said was too expensive and the wrong stuff to use on a cardboard/plywood rocket :
https://duplicolor.com/product/paint-shop-automotive-lacquer-finish-system
And I sprayed the parts in this :
https://www.walmart.com/ip/Honey-Can-Do-36-Wardrobe/17108665
And even after screwing up setting up the gun several times, once I figured it out ( https://www.how-to-build-hotrods.com/set-up-hvlp.html ), I sprayed for several hours (2 coats of primer, both sanded, 2 coats of color, 2 coats of sparkle, and 3 coats of clear) without any problems at all or the compressor running like a scalded dog.
I got one of the best paint jobs that Ive ever done, and certainly one of the top in my local area (but still well short of Nathans legendary paint!). The clubs that I launch with like what I do with rattle bombs and some prep work, and theyve absolutely pooped their pants on my DX3 paint job.
Since going HVLP, I use less paint, get better coverage, get better surfaces, get all the colors Ive ever wanted, and there is almost NO overspray whatsoever. Its an investment initially, but Ive found it to enhance greatly my MP/HP rocket finishes.
Bottom line is, test YOUR set up. If it does what YOU want it to do, go for it (and to heck with the haters that say you have to have a jumbo tank and a professional quality gun).
Glad I just caught this. Thanks for the detailed info and links! Saved to my onenote! That rocket looks REALLY Nice!
I thought I would post an update.
As I mentioned in a previous post, after scouring home shop, compressor and HVLP forums, I ended up designing a cooling rack (for lack of a better term) for my compressor/HVLP setup. If you did not read my previous post, essentially the idea is that the air off the compressor is hot, so if you build a "cooling rack it will allow the hot air to cool and condense in the rack. This will result in less moister hitting your trap. In my case I also added a second moister trap/air filter, as discussed in an earlier post. No doubt this is overkill for my needs, however I am confident that my moister issues are a thing of the past, which was the point.
Below is what I have so far. Sadly a slow start getting parts, changing my mind, breaking parts, getting replacement parts, etc., plus work has me extremely busy, so I have very little time for anything else. The vertical component, that is two 48" iron pipes, will be repeated two more times for a total of 6 x 48" iron pipes. The vertical components, plus the bends and other pipes, I should be looking at about 30ish feet before it hits my filter. 25'-50' is the recommended length for this type of design so I should be good. I opted for iron over copper but I can tell you that it is much harder to work with and if I were to do it again I would go copper...that is for anyone considering this.
The first vertical section on the left is not fastened to the wall yet, but everything else is all complete.
As I mentioned in a previous post, after scouring home shop, compressor and HVLP forums, I ended up designing a cooling rack (for lack of a better term) for my compressor/HVLP setup. If you did not read my previous post, essentially the idea is that the air off the compressor is hot, so if you build a "cooling rack it will allow the hot air to cool and condense in the rack. This will result in less moister hitting your trap. In my case I also added a second moister trap/air filter, as discussed in an earlier post. No doubt this is overkill for my needs, however I am confident that my moister issues are a thing of the past, which was the point.
Below is what I have so far. Sadly a slow start getting parts, changing my mind, breaking parts, getting replacement parts, etc., plus work has me extremely busy, so I have very little time for anything else. The vertical component, that is two 48" iron pipes, will be repeated two more times for a total of 6 x 48" iron pipes. The vertical components, plus the bends and other pipes, I should be looking at about 30ish feet before it hits my filter. 25'-50' is the recommended length for this type of design so I should be good. I opted for iron over copper but I can tell you that it is much harder to work with and if I were to do it again I would go copper...that is for anyone considering this.
The first vertical section on the left is not fastened to the wall yet, but everything else is all complete.
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I like where you're going with that Glenn.
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lookin good!
Thanks. I finally finished and tested the system last night. I had one small leak on a union, that a 1/8 turn fixed, and the difference in performance from what I had is noticeably different. I know that may seem a bit hard to believe but I had too many restrictions on my old setup and with this over-sized setup my bottleneck is now the compressor, which is not hard to see. With the previous setup I had to play with it to get it right and I was just on the edge of being able to use my HVLP. Now I have a lot of movement up and down, and it is much easier to keep it in my target range at the gun.
Also the air is very dry, and with the filter I am assuming cleaner although I never noticed a problem with the air cleanliness so this is just a bonus. So to sum it up my moister issue, gone, the performance issues, gone!
I also ordered the two HVLP guns I mentioned before, so I will now have a dedicated primer 1.8, base 1.4 and top coat 1.3. The only problem I see with this setup now is that I have no excuses for crappy paint jobs.
Nice!
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Just discovered this thread. Awesome info here. Answered all of my current HVLP questions.
Thx.
Thx.
1.6-1.8 is fine for most primers. For automotive filling primers, normally reduced, this is what I use. For polyester, a 1.8 is good. You could use larger. For years, one of my favorite nitro guns had a 2.0 tip on a pressure pot, it was very fast. For base, a 1.2-1.3 is sufficient. Base usually reduces 1:1, or more, and is supposed to be as thin as possible while providing all the color necessary. For clear urethanes and nitrocellulose lacquers, a 1.3 - 1.4 is good. Or bigger with nitro, if you feel like it. Technique can over rule most any of this, and while a decent gun is important, the operator is most important.
The 3M PPS system is awesome, if a little expensive to get set up. Highly recommended.
I have a rotary screw compressor that outputs 24cfm at 120psi. This goes into about 60' of 1" copper, which is sloped into down pipe drains. and then into a couple of coalescing filters, a silica media desiccant filter, another coalescing filter, and a 3/4" regulator. Then into a 25' 3/8" Devilbiss HVLP hose with HVLP specific air fittings. I use high quality gun regulators on every gun, and also inline air filters at each gun. I have 13 different guns for different purposes. My main guns are 3 Iwata LPH-400's. I have a spray booth and a separate paint mixing room.
For HVLP guns, a good regulator at the gun is almost a necessity. There are very few situations where it will not make a noticeable difference when spraying things like clear gloss.
Where a better gun will make a difference, providing that the operator is sufficiently experienced, is in helping to atomize the spray more evenly and better so that a fully wetted coat that flows together with minimal spray texture, and with less overspray can be more easily achieved. If you can consistently leave a glassy finish out of the gun that barely needs rubbing out and polishing, that is one thing, but even the best 'out of the gun' finish still shows some texture. Wetsanding texture from a finish into a 'dead flat' surface does not reflect good spraying. Every finish behaves differently, even among a single manufacturers range of clears, for example. Ideally, a freshly sprayed coat will just look glassy wet, no dry areas, no runs or sags, and evenly glassy everywhere. Most people who are new to spraying, struggle with this. An 'eye' must be developed for watching the spray droplets flow into each other as the hit the surface, and then a 'feel, for the amount of overlap, and how spray fan distribution is affected by different shapes such as round surfaces and inside corners, etc.
When the spraying is going as it should, a fresh wet film should flow together fully wetted, with no granularity (too dry) or wavy ripply (too wet) or orange peely (reduction or atomization issues, or too wet). Inside corners such as where the fins meet the tubes are the places where excess wet or dry spray conditions will exist.
Every gun sprays slightly different. A good gun that is matched to your finish is a joy to use. I considered earlier about posting that 'no way, the TCP guns are junk', but I realized that not everyone will recognize the difference between one of those, and a $600 Sata or Iwata. And, for the hobbyest, or for non critical or intensive professional use, that is fine. The TCP guns work, but a good gun will work much better. Nitro is a more forgiving finish than urethanes, and an expensive urethane through a cheap gun could likely leave one with less than stellar results. Urethane clears are not very forgiving, and they are expensive.
The operator is the most important element here. A skilled operator will notice shortcomings in a cheap gun, and a great gun will not make up for lack of actual spray experience.
One of the coolest pieces of spray gear, though, I mention it again, is the 3M PPS system. The 'mini's' would be ideal for painting most rockets. The initial outlay costs will be realized in not too long, returned in less time spent cleaning up, better cleanup, and much less solvent used for cleanup. I have been using the PPS system for the past 5 years or so, and love it, no looking back.
Accuspray makes some very good guns that are at the lower end of the price spectrum in professional spray guns. As a professional finisher, no TCP, Harbor Freight, or other similar guns, no way, no how, not going there. For a hobbiest that only rarely sprays, I might have difficulty justifying the cost of a good gun, though the resuts would be noticeable to anyone with a reasonable amout of spray experience.
For a hobbyest, I would be thinking of an HVLP turbine unit, a 4 stage turbine with excellent air filtration. A used system can be found on ebay for $600ish, and with care, a minimally used unit can be found. A good HVLP turbine setup solves the problem of air compressors, airline contaminants, and an air distribution system, filtration, and a good setup can be fitted with different needle / fluid tips in order to accomidate everything from sprayig thin shellac through thick latex paint. A good HVLP turbine system is a professional tool.
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