HVLP Guns: Gravity Vs Siphon, CFM and PSI - created 02-27-2004
Pedro - 02/27/2004.19:02:03
Hi, I've been through the archives and still have some questions about HVLP.
First, what are the advantages/disadvantages to using gravity guns vs. siphon feed guns. Second, when choosing a turbine, what CFM and PSI should I look for if I want to spray Nitro or Waterborne finishes. I'm looking at the Turbinaire MiniPro Plus Model 1235, it's a 3 stage (what does that really mean?) 110 CFM @ 6 PSI. Also, I know all stainless steel is the way to go for waterborne, it is ok for nitro too?
Peter, I can answer the first question to a degree but the full advantages will be more apparent when you have used both. There are really no disadvantages in using gravity feed unless you have used siphon for so long that the change is awkward. The pluses are many, here is a few.
They use less finish to do the job so you save on materials. You will use less air from the compressor so it will last longer. They are easier to clean and maintain. Gravity feeds can be adjusted to spray small areas better than a siphon. The primary advantage to a gravity is that you don't use air pressure to move the fluids in the gun, so a smaller compressor works as good as a big one.
One other thing, less overspray is less stuff that you will be breathing, so your respirator will need less cartridge changes. The gravity feed is superior in all perfomance aspects. It will spray anything that is thin enough to flow as well as materials that are to thick to spray with a siphon. As far the stainless steel parts go, the fluid passages are the only real concern. I have seen waterbase stuff corrode the insides of spray guns so don't leave it in the gun, stainless or otherwise.
I have used the turbine kind before and they cost too much for what you get, so I use gravity feed only. The money spent on a turbine will be better spent on lutherie tools. 3 stage just means that the air is compressed three times. A two stage air compressor takes the air from the first cylinder and compresses it again, giving a higher pressure. This is just a three stage turbine compressor. Stainless will work for just about any finish, but ask the supplier or the manufacturer to be sure. I can see no reason that nitro would not work.
My advice is buy a gravity feed and a good quality compressor. I use a Sharpe SGF98 HVLP for my gun. By the way there is a reason why none of the painters I see on the Discovery channel programs, are using a siphon or turbine HVLP
Bill Moll in another thread said that he uses a $19.95 Chinese made auto detailing gun to spray with so it is more the finisher than the equipment. This has been my experience also. That said, I still say go with a gravity feed.
I have read that an HVLP conversion gun (that runs off a regular air compressor) gives a smoother finish when using lacquer than a true HVLP gun running off a turbine.
And yes, a stainless steel fluid path gun will work fine with lacquer.
"I have read that an HVLP conversion gun (that runs off a regular air compressor) gives a smoother finish when using lacquer than a true HVLP gun running off a turbine."
I had not heard that Barry but it follows my experience. I think when the finish is an evaporative type the chance of "orange peel" might be greater with a turbine. Would that be the converted siphon type (bottom feed) that you are talking about?
For four years and many refinishes, I've used a cheap Hobby rated HVLP turbine (single stage) and the supplied bottom feed plastic suction gun (very simple, one needle with spring and adjuster behind, one nozzle, one bypass fan nozzle on the front which rotates through 360. Adjusts from a little to a lot and the little for obvious reasons has a narrower fan pattern than a lot, very easy to control) for spraying nitro. I also have a compressor and standard guns but reach for the HVLP all the time. When it expires I'll buy another exactly the same, I don't see the need for anything more fancy, I'm delighted with the results, and more importantly, so are my customers. I sprayed outside in (slightly) sub zero temperatures yesterday without any problem, I love it (and as a bonus I could treat my hands to a blast of warm air now and again to make things more bearable)!
Get a copy of the April 2004 Fine Woodworking magazine at your local bookstore. It has a good article about HVLP and set ups. The only drawback I remember it mentioning for the gravity feed gun is that it's harder to get into tight places. (in between shelves etc.) which shouldn't be a problem with musical instruments. :-) ) IT also has a detailed drawing explaining the operation etc. According to the article, a finish (n scrap naturally) resemling orange peel means the preasure is low and you turn it up by 5 PSI. They also suggest the use of a mini regulator at the gun on a conversion unit as well as inline filters. At the back of the mag is also an article on using foil covered foam insulation sheets to make a quick collapsible spray booth to fit into your garage door opening.
RP, No, the HVLP conversion guns can be EITHER gravity or sipon feed. I recently bouth a gravity feed conversion gun and am very happy with it.
And a gravity feed will utilize heavier finishes without thinning where a siphon will have a harder time of it with thicker finishes.
Thanks for all the input everyone. I found a turbinaire 1260 HVLP unit for sale at a local home depot tool rental, I got an incredible deal on it and they say it's only been used twice. I'm cleaning it up and looking for a new stainless gun. I'll let everyone know how things go with it. Everyone seems to have an opinion on every aspect of this topic which I find fascinating and frustrating at the same time. I'm just glad to be moving away from spray cans, preval sprayers, air brushes, and foam brushes. They're all crap and a waste of time, money and effort.
Don't forget to get strainers and if you get a gravity feed gun a holder unit that will also hold the strainer for when you fill the cup. Much neater and easier working. :-)
"RP, No, the HVLP conversion guns can be EITHER gravity or sipon feed"
I am aware of that Barry, I was referring to your statement about conversion guns giving a smoother finish as opposed to the turbine. Did what you read say that was true for both types or just one? I was asking for a clarification I wasn't lost.
Oh, sorry RP, I misunderstood. The information I was referring to has been gleaned from several sources. A recent article in Fine Woodworking had a reference to this difference in conversion guns versus turbine. However, none of the sources I have seen specified that it was only specific to either gravity or sipon feed conversion guns. I understood that it related to all HVLP conversion guns. I believe the better atomization of a conversion gun is due to the smaller volume of air that moves through the gun compared to the turbine type.
Ok, I have the turbinaire turbine unit. I have read there are no gravity feed guns for use with a turbine. Is this true? I'm trying to determine what guns can be used. I need to keep it under $200. And I'm spraying waterbased finish so it must be stainless steel. Suggestions?
Peter, I saw some el cheapo SS gun kits in Lowes the other week and if memory serves (don't hold me to it though) the were for turbine or compressor. I think they had some of each. I haven't seen in the article in the April FWW mag that it says they don't have gravity feed cups for the turbines specifically, other than a side bar that shows a turbine with a siphon cup and lists, suction, gravit and pressure feeds for compressor driven HVLP guns. So you may be limited to a suction/siphon feed gun with the turbine after all. But check with your local Lowes, HD and auto body supply places for deals on guns etc. :-) Hope that helps some.
Dennis, what's an SS Gun? I think the deal with the turbine guns is they need to have a pressurized cup in order to deliver the material. I read that there are no gravity feed guns for true HVLP on the Turbinaire website. Then I found a gravity feed with a pressurized cup! Man this is confusing.
I've got a CH gun that looks pretty cheapo, and since there is no model number I assume CH only makes one HVLP gun. THey claim that it's stainless steel for all the wetted parts. However I've yet to hear rave reviews of CH stuff in HVLP.
Thanks,Barry. I always try to keep current on tools and techniques so your response was important to my knowledge base.
"I have read there are no gravity feed guns for use with a turbine."
Not true Peter, they do make gravity feed HVLP turbine systems. However one of the reasons my advice was to get a gravity feed and a compressor is cost. Finding a gravity feed HVLP turbine gun might be pricey. Unless I am mistaken SS is stainless steel.
I found a gravity system by Lex-Aire that has a three stage turbine. The model is LX-60C. They also make a gravity gun that can be used with any turbine. They call it Pro-Series "TA" Spray Gun. Obvious url. It is more than you wanted to spend however.
Peter, what's a "CH gun"?
Just a guess Hal, Campbell-Hausfield.
RP gets the the cookie!! SS = Stainless Steel. :-)
I'll have to check that web site then Peter. The FWW article didn't mention either way in definite whether gravity feed was just for conversion or not. But I'd trust RP about that. I did see a diagram for a preassurized system for conversion guns and see no reason why it couldn't be used with a turbine. The diagram I saw was for a siphon type gun though. THe article I read also didn't mention anything about SS being only for water based finishes either, which makes since as autobody shops use SS guns for their lacqeur all the time. :-) Just that gravity feed allows utilization of heavier finishes more easily and is easier to clean, yet harder to get into tight spaces like on cabinets etc. I don't see why a preassurized cup, whether it's remote or attched to the gun, either gravity feed or not wouldn't work as well as if not better than a normal gun on a Turbine or a compressor system. Other than a remote preassurized cup does engender more parts to clean. :-) I'm checking it all out to find the best operating/least mess to clean system I can get. :-) I hate the clean up part. But love the info from this thread. :-D
I'm going to Lowes today to check out what they have. If they have SS for cheap I will try it out and I'll try to document everything I do in the forum. I figure if I share my work here it will help others in my situation and speed up my learning process as well. I love this place!
Gravity Feed HVLP all the way!
Aaron, give us a bit more info...do you use compressed air or a turbine?
So what gun options are there for turbine users? That's my big problem right now. It seems like most HVLP guns are conversion guns. Is that true?
"So what gun options are there for turbine users?"."It seems like most HVLP guns are conversion guns. Is that true?"
Google is your friend here Peter , I got 77,400 hits on "HVLP". Just type in "HVLP" and search within those results with "turbine gun". I got 3,398 on that. Search "gravity feed" within that gets 648. Most of the HVLP guns at auto body supply shops are not what I would a "conversion" unless buying a HVLP to use with a standard compressor is considered that. What I call a conversion gun is one that has a new parts kit installed to pressurize the fluid cup.
RP, A conversion gun is exactly that, in everything I've read, it converts your standard high pressure air compressor into a soft spray HVLP spray system.
I believe all Turbine HVLP require that the cup is under pressure in order to get enough material to the tip. So not all HVLP guns are designed for use with a turbine. In fact, there are a ton of coversion guns available and very few turbine HVLP, or true HVLP, guns on the market. Therefore, I am asking if anyone here has discovered a good turbine driven HVLP gun.
"I believe all Turbine HVLP require that the cup is under pressure in order to get enough material to the tip"
My guess is that this is true. Probably more so with the siphon type as it has to be pushed up a tube first. I would go with a gravity feed type.
Everything points to gravity feed but I have read that gravity feed guns are not available for turbines. I wonder why? Any thoughts?
"I have read that gravity feed guns are not available for turbines."
Like I said in post #16, Lex-Aire makes the gravity feed Pro-Series "TA" Spray Gun, this is a turbine gun. Pay attention here I'm trying to help
The Sharpe is the closest to the price that you mentioned, the others are a little higher. These are all I have found so far. The Sharpe is probably a brand new gun as I could not find it on their website. But I found a website that will sell me one, (Topline Specialties .com) so I am reasonably sure that it is available.
I have used Sharpe products for more than twenty years on and off the job so I can vouch for their quality. I also own a Sharpe HVLP non turbine gun and I like it very much. I hope this helps a little? I can't comment on the other guns as have never used any of their products, so maybe you can research them and see what people say about them. I did find out something that I was not aware of with the turbine units. It appears that the bearings in the tubines will wear out pretty soon with constant daily use. So if it was me I would look at how long they will last and get a spare set just to be sure!
Peter,
Here's more info. . .I use a compressor (because I already had one), not a turbine. I've sprayed automotive paints prior to moving to woodworking, so I have some experience in this area (I've used both siphon feed and gravity feed).
Without getting into the siphon feed, here's the points on gravity feed HVLP - easier cleaning, less waste, easier cleaning, better control on seeing where the fluid "pick up" is (do you really know where the pick up tube on a siphon feed is at any given time?), easier cleaning.
If you look at Sata's high end gun, it's a digital gravity feed. Nice gun. I currently use a cheapo PC, but have access to a Sata mini which I personally haven't got the "feel" for just yet. BUT, you just cannot beat the quality of spray on the Sata. Aloha.