Equipment and ToolingQuality and Metrology

Programming Quality – Knowledge is just as important as the program when measuring with an automated CMM


Clamp the part to the surface plate. Enter a few parameters. Grab the joystick and go. When checking a hole location, or measuring the distance between two machined surfaces, that’s about all you need to know in terms of coordinate measuring machine (CMM) operation. Unfortunately, most inspection procedures are more complex, and good metrology requires a lot more than mastery of a few screen commands. Programming automated measuring equipment needs robust software, a sound program to drive the machine, and some old-fashioned inspection know-how.

Like hand-cranked engine lathes and series I knee mills, manual CMMs are quickly going the way of Gray-Dort Motors. “We still sell a fair number of basic CMMs for general shop use, where people need to do a simple layout or take a few quick measurements for a machine setup, but probably 75 per cent of the CMMs we sell today are automated,” says Peter Detmers, vice president of sales at Mitutoyo Canada, Mississauga, ON. That’s good news for those quality control people who suffer tennis elbow from shoving a probe around all day, but the move to automated CMMs presents a frightful burden: learning how to program.

It’s not as scary as it might sound. CMMs do not require complex G and M code programs to drive them through their elaborate dance. Most if not all CMM software packages offer predefined macros—bolt hole patterns, slots and surfaces, even screw threads can be automatically measured by answering a few basic questions on what you want the machine to do. And automated CMMs can be “taught” how to measure a workpiece by putting the machine into recording mode and manually driving the probe through the first measuring routine. Subsequent workpieces are then measured with the resultant program—take a few manual data points to tell the CMM where the part sits and how it’s oriented, then execute the recording. The CMM software remembers what you did last and drives the machine axes through the same steps.

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