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