Assessment and implementation of Global offset compensation method

Nowadays, the demand of tighter tolerance components requires more accurate machine tools with volumetric compensation. In mass production, post-machining inspection of the workpiece on a coordinate measuring machine (CMM) of all or just some control features of the parts provides statistical quality control information for all the parts and the variability of the manufacturing process. The paper explains the precision enhancement of machine tools according to Global offset, including parameter error modeling, identification and compensation. The method is utilizing the part quality CMM data to determine the specific compensation parameters that are used in the machine tool controller to minimize the machine tool errors. The aim of this method is to explain the compensation of multiple sources of errors including those affected by the rigid body behavior and the deformation due to dynamic forces, thermos-mechanical changes and backlash (that are repeatable from part-to-part) in a machine tool. Part deformation due to cutting and/or clamping forces that are repeatable can be also compensated. The 3D weighted least square fit is explained to determine the compensation parameters. It makes compensation easy and convenient using part measurement data. Simple scenarios are used to illustrate the capabilities of the Global offset compensation method based on a very simple part.