Sourcing a CMM

What would you do if a new piece of cutting-edge technology came falling out of the sky onto your workbench? Well, after you fix the hole in your shop roof, it'd probably be nice to get the part precisely measured onto a computer so you could mass produce it (and subsequently make millions of course). That's when you'd use a coordinate measuring machine (CMM).

(Credit: Mickeyholman.blogspot.com -->)

CMMs are nifty devices that take measurements of parts for applications such as reverse engineering your competition's products, testing, design, assessment, profiling, and so on and so forth. Traditional CMMs consist of three components: the machine, the probe, and the control or computing system. The machine controls a probe which measures and records the location/coordinates of different points on a part; these points are uploaded to a computer which can use them to map part dimensions.

(<-- Credit: Leader Metrology)

When sourcing a CMM, it's most important to size the equipment to the size of the parts being measured. The arms of a CMM probe may be flexible, but they do have a limited range of motion. Machines are specified based on the measuring length of each axis of motion. Other specifications include the resolution (how precise it can measure), the measuring speed of the device (hopefully not agonizingly slow), and the weight capacity (how much the part being measured can weigh).

Traditional CMMs are bench mount point probe devices, which physically touch the part to detect its position (as demonstrated in this video). But not all parts can be measured this way. More advanced measuring technologies use cameras and/or lasers to record coordinates, and some are even handheld to provide portability and flexibility.

For a one-time measurement, it may be best to use a CMM service to do the measuring for you. But if your company finds itself profiling parts often, it may be necessary to source out a new coordinate measuring machine to make precise part-dimensioning possible. When you do, take a look at GlobalSpec's Coordinate Measuring Machine Selection Guide for a more thorough explanation of the selection process.