Compare COORDINATE MEASURING MACHINES. Coordinate measuring machines are measuring systems that move a measuring probe to coordinate points on a work piece. The CMM or coordinate measuring machine system has three important elements, the mechanical machine structure, the measuring probe and the computer (hardware and software).

The three most important parameters of coordinate measuring are the measuring distances of the X,Y, and Z axes; the measuring resolution, and the maximum weight of the item being measured. The measuring distance is the total travel that the probe can move in each, the X,Y, and Z direction.

.This section covers bridge style CMM only. The size of the items to be measured can range from a few centimeters to over a meter in size. In all cases, the volume space under the bridge has to be larger than the measuring range specified for any given model. Most important is the height available under the probe tip (Z axis) and the width on the table (Y axis). The work surface of most CMMs made of granite. The X and Y axes are moved with linear electric motors or ball screws and ride on air bearings. The Z axis is driven by ball screws or pneumatically. The software allows the programming of coordinate points to be measured or shapes and contours that the probe will follow. The degree of difficulty to program the measurements will depend on the software as well as the type of measuring probe. The machine manufacturers state machine performance based on their own software and recommended probes.

Ambient temperature is an important factor when considering the accuracy of the coordinate measuring machine system. 20 C +/- 2 C is the standard temperature range. Location of the system is therefore an important consideration. Many models have temperature compensation in their dimensional readouts. Considering the thermal expansion of each component in the machine and measuring the component temperatures, thermal correction factors are calculated and applied to each measurement.