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The higher CFM needs of a mini spray gun versus an airbrush, and one way to get it

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  • Member since
    January, 2017
The higher CFM needs of a mini spray gun versus an airbrush, and one way to get it
Posted by Jim G on Sunday, February 05, 2017 10:59 AM

A number of online videos and articles correctly suggest that when painting model vehicles, especially larger scale cars/trucks, ships, or planes, it is better to use a mini spray gun than an airbrush, in order to get a very significantly wider fan pattern capability, which means less individual passes, which means a more uniform paint thickness, and less opportunities for dust and other problems to develop (the much wider fan pattern means that the actual total spraying time is much shorter than with an airbrush).

I went with an Iwata mini spray gun, the LPH-50 with 0.6 mm nozzle, for exactly these reasons. The LPH-50 gives me a fan pattern width range of 1/8" to 2-1/2".

HOWEVER, pay attention to your propellant source's CFM capacity.

Because mini spray guns can shoot a much wider fan pattern, they need a much larger sustained CFM capability from your propellant source. If you do not provide it, the gun is "starved" for air, and you won't be able to use that wide pattern!

For example, the Iwata LPH-50 I bought needs 1.8 CFM from its air source, if run at maximum capability. This is way beyond what most "airbrush" compressors can provide, on a short burst basis (even with surge tank) let alone a sustained basis. In fact, in Iwata's own "airbrush" compressor lineup, only the top couple of compressors can supply 1.8 CFM, and they are very costly (About $700 plus taxes and shipping in Canada, somewhat less in the U,S.).

For further "proof" of the need for larger CFM, just look at the size of the "plumbing" used in a true mini spray gun: it's 1/4" NPT versus the 1/8" used to feed airbrushes. 1/4 versus 1/8 means 4 times the airflow capability (airflow capability is proportional to cross-sectional area, which is proportional to square of the radius).

I went with a different "solution" for the air source. I will be using a Nitrogen tank. The Nitrogen tank comes filled to 2100 psi, and has the following pluses:

- No need for a water filter, as Nitroge gas comes "pure" with no water int it, and since you are not running a compressor, you don't create any water in it either

- VERY high sustained CMF capability - basically limited by the clear diameter of your "plumbing" (regulators, hose, quick disconnects, etc) after the Nitrogen tank

- None of the "icing" problems of a CO2 source (CO2 tanks or cans cool very appreciably as the liquid CO2 inside them converts to gas under use, and can actually ice up shut when used for longer bursts, plus the varying temperature is obviously destructive to your carefully set-up paint/air mix at the spray nozzle)

- Much less costly than a compressor large enough to properly feed a mini spray gun, even when taking into account of the cost of periodic refills, since the actual spraying time with a spray gun versus an airbrush on a model is measured in seconds, not minutes

- Nitrogen is non-reactive and benign, and 78% of normal ambient air is Nitrogen, so spraying Nitrogen into the room does not hurt you

- No noise, unlike a compressor (very important to me, as my wife wants "no noise" and we live in a condo)

- No vibration, unlike a compressor (very important to me as my wife wants "no noise" and we live in a condo)

- The Nitrogen tank with high pressure regulator setup takes less floor space than a compressor when in use or storage

The disadvantages of the Nitrogen tank are:

- Cost of periodic refills ($35 where I am located), but these will be pretty infrequent

- Some reasonable care is required in handling and securing the tank, since if you drop it or knock it over, and manage to break the regulator setup in doing so, you could have a short range "missile" as the 2100 psi driven leak creates a "rocket"

Nitrogen is easy to find locally. I got my tank and high pressure Nitrogen-configured regulator from the local PraxAir shop that supplies industrial gas users, welders, and hospitals. The initial setup cost can range from about $100 if you buy the high pressure regulator and rent the tank (tank rental is about $35 per year), to $350 if you buy the high pressure regulator and the Nitrogen tank. (These are Canadian prices - U.S. prices are likely at least 25% lower).

The output of the high pressure regulator might be, like on mine, a special thread that requires an adaptor to connect to a tpyical spray gun hose.

You also should get a physically small, low pressure regulator, that mounts just before the quick disconnect and spray gun, so that you can conveniently and accurately set the input pressure to the spray gun. Depending upon the tpye of spray gun (HPLV, LPLV, etc), the input pressure to the gun needs to be as low as about 10 psi or as high as 50 psi, and that range would be both inconvenient and inaccurate to try to set on a high pressure gage with a too-broad psi range located at the propellant source.

I am waiting for some paint and accessories to arrive before I can actually test my setup, but it should work pretty well once I have everything in hand.

Jim G

  • Member since
    August, 2016
  • From: Wisconsin
Posted by jwrass14 on Sunday, February 05, 2017 1:52 PM

For example, the Iwata LPH-50 I bought needs 1.8 CFM from its air source, if run at maximum capability. This is way beyond what most "airbrush" compressors can provide, on a short burst basis (even with surge tank) let alone a sustained basis.

Dear Jim,

I think your intentions here are pure as you and have had communications on the subject of the LPH-50, However I would take some caution before you give advice on what is and isn't a good air source and here's why.

As you and I have discussed I own two LPH-50s that I use in my 1:1 Custom Paint Business and am very familiar with what the LPH can and cannot do. With that said lets look at the air source the gun and proceedures.

#1) Nitrogen is absolutely a great air source!! I have a smaller set up (about the size of a scuba tank) that I use when I play road warrior.

#2) In my 45 years of painting as a professional I have never had to MAX out a gun (I may have but don't recall ever doing so) In fact I set my guns and spray patterns to atomize the paint at the minimum air pressure I can and still have a effiencent spray pattern and material transfer..... less air pressue = less over spray and material used.

#3) You can purchase a good nail gun pancake compressor for about $150.00. I own a Senco model PC1010N (on sale $99.00) that I use for modeling and it will take anything I throw at it when the LPH-50 is being used. The $700.00 Iwata compressor IMO would be a waste of money.... the only advantage with these units is they are super quiet. We could go down the road of calculating scfm and cfm as my primary job is as a Mechanical Engineer spending my entire career in the commercial HVAC arena to which I am very familar with those calculations. I feel It's pretty much a non issue in this curcumstance.

#4) I think you are getting way to hung up on published information, My experience has been that manufactures provide the Max (+ the non published 10% fudge factor) operating data to cover their butt!

#5) Perhaps a better approach for commenting on the performance of the equipment you will be getting is to actually use it and then report back with your findings. Published information and real world experience are two different worlds!

I'm not trying to sound like a know it all or to be harsh.... I just don't see how posting talking points is very useful. Agian the think it would be much more useful and relivent to actually push some paint through the equipment and then post your results.

Once you do that I would be very interested in your findngs.

Respectfully Submitted,

James Rasmussen / AKA Jimmy "RASS"

"I Have Flying Monkey's And I'm Not Afraid To Use Them"

  • Member since
    January, 2017
Posted by Jim G on Sunday, February 05, 2017 3:43 PM

Jimmy I see your point, but after I discovered the CFM requirements, I difured I should at least warn other modelers who might be thinking about getting a mini spray gun.

The pancake compressors you mention might work for some people, but I doubt their incredible nosie level would be acceptable for anyone working indoors! I have had 2 of those  compressors, and they are loud even outdoors, let alone indoors! In my situation, a lower noise level is very important, and judging by the way the super quiet compressors are marketed, it sounds like it is important to a lot of airbrushers.

As for whether a specific compressor's output is adequate, here's a question I have: How would anyone know if their compressor is limiting their gun's output unless they are a pro very experienced in painting with strong compressors and large capacity guns? If it's a hobbyist's first spray gun and first compressor, if their compressor hits its highest CFM capability "trying" unsuccessfully to keep up with the gun's capability, the only "symptom" the hobbyist would obviously see is that at some (premature) point of screwing out the fluid screw, he would get spattering or other symtpoms of excess paint to air ratio, and being inexperienced, he would have no idea that the compressor was under-delivering air. So, following the paint or gun manufacturer's directions, the hobbyist would reduce his paint flow and not realize that the compressor was what was limiting his output. Am I right or wrong on this? (I am definitely in the early learning curve and eager to learn!)

Jim G

  • Member since
    August, 2016
  • From: Wisconsin
Posted by jwrass14 on Sunday, February 05, 2017 9:51 PM

Jim,

I did give the the model # of the Senco compressor perhaps I should have elaborated on it's performance. I too have a standard pancake type compressor a Rollaire for running trim nailers and indeed it is noisy. I went shopping for another compressor just to use for modeling as my RollAire is 25 years old and my thinking was with advacement in technology the compressors would be less noisy, for the most part they were not! Every compressor I had a interest in I had the sales associate at the Big Box stores plug in the display model so I could hear them run. Then I ran into the Senco unit and it is less loud than a average vacumm cleaner.

I know alot of Airbrush Artists world wide and the topic of how loud ones compressor is has never been a topic of conversation.

I'm not sure if I totally understand your question on compressor/gun trouble shooting and may have blinders on as I have been doing this type of work for so long, however I will try to answer the best I can.

My proceedure for setting up any type of device that shoots paint is pretty much site, sound and of course experience. My regulators on my guns do not have read out dials on them as I pretty much know what 30 psi sounds like.... again experience.

The last place I would go in trouble shooting a gun would be the fluid nozzle setting, I would adjust in this order air pressure, fan and then fluid. A general rule of thumb for the fluid adjustment is 11/2 to 2 turns out. I have mine at 2 out and never touch it!

There are so many hypotheticals we could come up with.... My thinking would be if I hear a drop in air pressure (which you will hear) I would check my regulator and or let the compressor catch up which is not a big deal even with kandies. Is a insufficient air a pain..... Absolutely, is it the death of a good paint job no! 

When I paint site and sound are my best friends. I pay attention to the air pressure sound but more importantly is site.... I am dilligent in watching the paint hit the surface as to maintain proper overlap and film build up.

I hope this makes some kind of sense...

 

Jimmy "RASS" 

 

"I Have Flying Monkey's And I'm Not Afraid To Use Them"

  • Member since
    January, 2017
Posted by Jim G on Sunday, February 05, 2017 10:32 PM

Jimmy, yes, it makes sense. It works for you because you have a lot of experience. I don't, so I need to minimize any handicaps, which includes making sure that I understand the acceptable starting points for psi, fluid control setting, etc., so that I am "in the right ballpark", and then learn and fine tune from there.

As for compressor noise level, if you are only shopping for compressors at big box stores, you probably have no noise level concerns and so those compressors work fine for you. But someone painting in a condo or apartment, and esepcially if he/she has a spouse, the noise level is a HUGE concern, as it can be a showstopper for the hobby!

The bog box compressors generally DO have sufficient CFM to run the airbrushes or mini guns that a hobbyist would use. But their noise level is the disqualifier for a home setting or a commercial aertists located within a building with other businesses. The airbrush and minigun manufacturers know this and this is why the offer the very quiet, but very costly compressors at the top of their lineups.

In fact, I learned during my research that airbrushes are used notonly for painting but also for professional cosmetic application and for fingernail decorating. The people that use airbrushes in those environments MUST have very quiet compressors, as neither they or their customers would tolerate the noise levels of the big box compressors!

Jim G

  • Member since
    August, 2016
  • From: Wisconsin
Posted by jwrass14 on Monday, February 06, 2017 10:39 PM

Hey Jim,

You certainly have done your homework.... A+!

I have done finger nails and cosmetics at airbush funtions and it's a blast!... Iv'e had the please to paint a few..... You can fill in the blanks....

A bit of Airbrush trivia.... Airbrushes were used for years in photo touch ups and enhancements (old school Photoshop) they were also used extensivly in the colorization of photos that were popular in the late 50s and early 60s.

IMO they gained thier biggest notoriety of the Van Craze of the 70s!

Peace, Jimmy "RASS"

 

 

 

 

 

 

 

 

"I Have Flying Monkey's And I'm Not Afraid To Use Them"

  • Member since
    January, 2017
Posted by Jim G on Monday, February 06, 2017 10:50 PM

"Iv'e had the please to paint a few..... You can fill in the blanks..."

Ok, NOW watch the young guys line up to learn how to airbrush . . . :)

Jim G

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