Calibration Criteria for Coordinate Measuring Machines

The calibration of coordinate measuring machines mainly addresses the classic problem of identifying six or more features of the measuring machine and establishing its local coordinate system. The calibration of a CMM must meet the following criteria:

First, the vector directions of the three selected points shall be basically consistent and used for leveling the part.

Second, the vector directions of the subsequent two selected points shall also be basically consistent, and substantially perpendicular to the vector directions of the first three points, mainly used for aligning the orientation of the part.

Third, the vector direction of the sixth point shall be substantially perpendicular to the vector directions of the first five points and used to define the origin of coordinates.

In addition, the more features selected, the higher the corresponding calibration accuracy.

Therefore, this method is very effective for calibrating individual parts. However, for mass-produced products, this method is obviously inefficient. Apart from repeating the calibration process for individual parts, there is no effective method specially for calibrating mass products and evaluating errors for the time being. Normally, the calibration and error evaluation method for mass products can adopt manual calibration of reference parts. For parts clamped on the same worktable, the reference point method can be adopted to enable automatic calibration by the program.