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Originally Posted by pklin
Hello all,
Trying to start out with a little benchtop blasting cabinet requiring approximately 5 CFM @ 80-90 PSI. I have noticed that a lot of the compressor found in home improvement stores don't match up to this requirement, unless you go up in horsepower and price which defeats the purpose of setting up an affordable, beginner home blasting hobby. My question is, if I got the aforementioned cabinet, and got a compressor that is rated at 4.2 CFM @ 90 PSI, how will this effect the blasting operation? I will be blasting mostly small parts, so I was also looking into pencil blasting cabinets that only require 1.5+- CFM at low PSI. Should I consider pencil blasting cabinets as solution? Thank you.
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I can tell you, based on a lot of "experience" in my early years of sand blasting that while it matters some what type/size of sand blasting unit you have (syphon feed blasters consume more air [90psi] for less results than a Pressure type blaster [can be used at 40-50psi]), the "biggie" is the size and quality of the Air Compressor that determines the out come..
At a minimum, you will need a "real" Five Horsepower Motor (not some overseas 1/2hp motor with five capacitors on it to get it to "rate" at 5hp-- the "Black Max" compressor built in the early 90's was a perfect "bad example"!!), a Twin Cylinder, Two Stage Compressor and a 60 to 80 gallon tank..
The "Two Stage" compressor is important, the first cylinder sucks in air and compresses it into the second cylinder which compresses it even more.. This is "where" and "how" your higher CFM is created.
If you attempt to sandblast with an undersized compressor, you will run the air pressure down, the sand blaster loses effectiveness, the compressor never shuts off causing the compressed air to become super-heated and with that heat comes moisture that gets sprayed onto your bare metal parts just like coming out of a garden hose.. and even if you have water/oil filters, they become saturated and water still gets on your parts creating "instant rust"!!
I have a compressor as described above and use it to run a 100lb (weight of capacity of sand) Pressure Blaster.. I can blast an entire automobile frame or body without "taxing" the compressor as it "cycles" (pumps up to pressure, shuts off for a few minutes then cranks back up) while I'm blasting.. The key is that cycling like this gives the compressor a "chance to rest" and "cool" a bit (not much) before going back to work. The best compressor I've ever used was a 25 horse "twin screw" blower type unit.. that puppy cranked out the wind in short order.. but not all of us have the cubic dollars to buy one!
It is also important to note that I have three water filters between the compressor and the sandblaster.. the first one is fitted right at the outlet of the compressor's tank and, of course, it the first to become saturated. The second filter is at the regulator where my air hose connects, it takes longer to saturate, and the last one in at the inlet of the blaster itself.. rarely do I have to drain water out of it.. Another "key factor" in reducing water in the air lines is to use "Black Iron" pipe, run it "out and up" from the compressor to the ceiling, have "condensing loops" at every "down leg", as well as a length of pipe (about two feet) extending below the "tee" where the filter and hose connections are.. this allows condensed water to run down into the "trap" instead of passing thru the filters..
Believe it or not, there is a whole science about the proper way to run air lines that result in the least amount of pass-thru moisture.
And in media-blasting, powdercoating and spray painting, we need ALL the help we can get to keep moisture out of our finished products! ;-}
Lastly, on your question about using a "pencil blaster".. If you intend on blasting anything bigger than toothpick size, you ae going to need a "real" compressor and a "real" pressure blaster.. anything less is a waste of time, in my opinion..
Charles.