Calibration Process May Improve CNC Accuracy

An improved calibration process for machining and milling tools may help reduce flaws in the large parts manufactured for the aircraft and heavy equipment industries.

The process replaces the current piecemeal approach to correcting the inherent geometric errors in computer-numerically controlled (CNC) machinery.

Manufacturers calibrate machine tools to compensate for these errors. However, they use several approaches, fixing pieces of the problem. This process can be laborious, time-consuming, and expensive.

Creamer and her team developed a model for identifying errors and generating compensation tables to guide corrections. These tables can be programmed into a CNC machine to compensate for known errors.

Working with the Boeing Research and Technology center in St. Louis, the team measured motion of all axes of a CNC machine with a laser tracker. Based on these measurements, Creamer created compensation tables for several different machine tools.

This calibration methodology may represent an advance for large-part manufacturing. For example, an airplane wing can be 120 feet long; holding errors to five thousandths of an inch over a part that size will be more achievable with this more comprehensive process.