Machine tool analyzer: a device for identifying 13 position-independent geometric errors for five-axis machine tools

We introduce a prototype "machine tool analyzer" (MTA), consisting of a nest of five displacement sensors and a dual-ball system with two centering structures, designed to identify 13 position-independent geometric errors (PIGEs) in five-axis machine tools. The 13 PIGEs include three squareness errors in the three linear axes, two squareness errors and two offset errors in the rotary/tilting axis, and two squareness errors in the spindle axis. The MTA completes four circular paths, during which an identification algorithm identifies thirteen possible PIGEs and set-up errors. The MTA was applied to a commercial five-axis machine tool with a swivel head/rotary table and verified experimentally. Cost-effective measurements were achieved using a single set-up of the nest and associated system. In addition, a circular test using a double ball-bar was used to test the volumetric accuracy of the five-axis machine tool and verify the identified PIGEs. The maximum deviation, minimum deviation, and PV values in the circular test were 109, 55, and 55 mu m, respectively, without compensation for errors imparted by the PIGEs, and 38, 5, and 33 mu m, respectively, with compensation. This demonstrated the validity of the proposed method.