Compressors and Random-Orbit Air Sanders

      Pneumatic sanders are air hogs — you need a high-capacity compressor rated for continuous duty. July 16, 2008

So we switched to air sanders recently and I'm reminded why I didn't do it before. We have a Champion 5hp 80 gal compressor with an aftercooler that runs our whole shop. It's rated to deliver 19.1 cfm at 125 psi. Today, it would not get above 50 psi for as long as I was watching it. The bander and point to point would not run.

At any one time, we will be running 1 air assisted airless gun in the paint shop, 2 air sanders, 2 nail guns, 1 guy will be blowing something off, and 2 out of 3 pieces of equipment will be running that require air, such as the wide belt, the point to point, and the bander.

Can anyone tell me what size compressor I need if I dedicate the one I have to the paint shop? I know, I can look at the cfm ratings of all the tools, but I'd rather just hear your opinions based on experience.

Forum Responses
(Cabinetmaking Forum)
From contributor G:
We have a 10 hp Champion. It is a very good comp but it is all it or any 10 hp can do to keep up with two RO sanders. RO sanders are worth all the air they consume in my book. Sounds to me like you need a 15-20 hp. Keep in mind many of your tools require air pressure but not much volume. You might also want to consider a rotary comp. I like the two comp idea. If one goes down, the entire shop does not come to a standstill. Talk to a reliable salesman.

From contributor D:
DA sanders are air hogs - this much you know already. Most of these types of sanders require something like 10-20 cfm at 90 psi. There are a couple of things to consider when shopping for a new compressor: Air volume requirements (cfm) and duty cycle, the percent of time a unit will actually be making air. Most piston-style compressors aren't rated for high duty cycles, so you can burn one up pretty fast with a lot of air demand. We cooked a 10hp Ingersoll two-stage compressor in a little less than two years.

The best and most productive compressor is a rotary screw style - these units have a duty cycle of 100%, or said a different way, they can make air constantly. A typical two-stage piston compressor might have a duty cycle in the 35% range. We run a 10hp rotary that keeps up with multiple air sanders, wide belt sander, multiple machines with air-actuated systems and an air-assisted airless spray system. System pressure is kept at or below 125 psi and regulated at individual machines to their requirements.

Rotary screw compressors are more expensive than their piston brothers, but they will run a long time with normal maintenance (oil and filters). Our oldest one (we have two, one online and one as a backup) has over 7500 hours on it with no major maintenance.

From contributor J:
Another thing that may help you out a little is to have a bigger reserve tank. A shop I worked at in the past had 2 rotary screw compressors and a rather large holding tank. I'd guess at least 4' in diameter by about 10' in height, no idea how many gals but likely 1k or maybe more. You would still need a bigger compressor, but it may give you a little extra help to even out the surges.

From contributor V:
Just for what it’s worth, you will save more in labor in the first year than what the new compressor would cost. However you can simply just add another compressor to handle just the sanders and be done.

From the original questioner:
I realize the sanders are nice, but that nice? Aside from the comfort level, they don't sand any better, or faster, fFrom what I've experienced anyway. I should point out that just because I bought 5 doesn't mean I have 5 full time sanders. That's simply 1 for each station. So maybe our labor savings isn't what you're thinking.

From contributor V:
I was thinking labor. Do you have 3/32 or 3/16 orbit? I have been using them for years and they sand 3 times faster than regular electrics. Contributor J was right about reserve. I added a 30 gal reserve to mine at one time and that helped a lot.

From the original questioner:
Ok, I'll admit my experience amounts to about 20 minutes of sanding time. I bought all 3/32 orbits because we don't do a lot of aggressive sanding. We outsource our doors and most of our hardwood comes off an S4S planer. So the majority of sanding is on smooth wood and veneers, and we rarely use anything more than 180 grit.

Does anyone else second that I would save significant time, enough to offset the cost of a very expensive compressor? We just haven't used them enough to know.

From contributor V:
Now that you have actually given us enough info to make a better decision. If you never use over 180 and never have to do any aggressive sanding. Stick with electric sanders.

From the original questioner:
Naturally, my salesman didn't tell me that.

From contributor B:
You can't run a DA on a lower pressure then suggested the finish will suffer. You also can't set a regulator to that pressure and think you have it. You should make a test gauge set up that will allow you to check pressure at the tool as you are running. For us to get 90 at the tool running we run the regulators that are far from the compressor at 125#.

I think you were air poor with your pre DA setup you just didn't know it. I would get a compressor guy in to check your situation. We have 7 DA potentially running at once.

We run 2 - 10hp compressors. One runs 5 guys fine based on how we operate. Pneumatics rule, we run Sioux screw guns and drills and Dynabrade sanders they all last forever (unless you drop them). Don’t give up the ship.

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