Tech Notes: Clean Air Lines

(Editor's Note: With this issue of the Newsletter, we introduce "Tech Notes." Our humble attempt to provide CMM owners and operators with helpful tips that will make their job easier and keep the service technician from the lab door.)

You've heard the old oil-change adage: pay a little now for a filter or pay a lot later for a new engine. Well the same can be said when it comes to the air supply on a coordinate measuring machine (CMM).

You can check and replace your compressor air line filters for less than $20, or you can wait until the air lines become contaminated, damaging the CMM and costing about a week of downtime and $8,000 for repairs.

We've seen it happen too many times. Oil and/or water gets into the air lines contaminating the air bearings, and causing amplifiers to blowout. At that point, the only thing you can do is replace everything.

But this is all too easy to avoid. It starts with the compressor filters and air line filters on your CMM. There are normally two filters -- the liquid separator filter and the particle filter -- that should be inspected once a week and replaced as needed.

Depending on the CMM and the compressor, there may be two filters on the CMM and two on the compressor. Each filter needs to be taken out and the element visibly inspected. It takes about 10 minutes.

The cubic-feet-per-minute output of your compressor will dictate which filters to use and how many. Each filter element costs under $20 and can be ordered from any good industrial equipment distributor.

We also recommend a refrigerant dryer be attached to the compressor to take the moisture out of the air before it is sent through the filters. This will prolong the life of the filters and help avoid contamination.

Of course, if you've got the money, the cleanest "air" to use is nitrogen. It's what NASCAR racers use with their pneumatic tools. However, it is very expensive and we know of only one company using it, and that's because they have other uses for the nitrogen. Of course you still need a liquid separator filter and you've got to check it once a week.

So, pay for the filters now, or pay for the replacement of air bearings, lines and who knows what else later. It's up to you.

Thom Hoey
EMD Systems Engineer

Electronic Measuring Devices, Inc. (EMD) is a reputable company manufacturing scanning heads and specialty CMMs. The newsletter is from Fall of 1998.