Assessing the Accuracy of Five Axis Machines by Comparing Machine Measurement Data with Test Work Piece Deviations

In aerospace industry the application of five axis machines is increasing and becoming common practice. The determination of the accuracy of such five axis machine however is often difficult or problematic. A significant increase is seen in the certification efforts involved for this industry sector.To assess the accuracy of a five axis machine within one minute a dedicated Rotary Inspector system has been developed by IBS Precision Engineering. With this measurement system a 3D measuring head is used in combination with a masterball while the machine executes a certain cycle using multiple machine axes simultaneously. Typical tests are specified in ISO10791-6 (e.g. AK1, BK4, CK4) and these are used in this paper to determine the machine's accuracy first, representing normal (milling) machine use. Usually test work pieces are made on a machine and its geometrical deviations are checked on a CMM for certification. The relation between these geometrical test work piece deviations and the measured ISO machine error parameters of the rotary axes is addressed in this paper. In this way the need of milling (many) test work pieces can be reduced significantly for certification purposes.