Identification of different geometric error models and definitions for the rotary axis of five-axis machine tools

Geometric errors are the major error sources of machine tools. Different geometric error models have been used in published studies according to the different definitions of geometric errors of the rotary axis. This is considerably dangerous as it makes the definition of geometric errors ambiguous and may reduce the effect of geometric error identification and compensation. This phenomenon has not been noticed yet. In this paper, another two used geometric error models of rotary axis are firstly introduced and analyzed, named as “Error first model” and “Motion first model”. These two models were both verified correctly by an example. After a detailed comparison, errors identified with these two models are discovered to have a certain relationship. “Error first model” is preferred for the modeling and definition of geometric errors of rotary axis. An experiment has been conducted on a 5-axis machine tool to demonstrate the correctness of our research. The results show that the identified geometric errors of rotary axis according to the two error models are greatly different and deserved to be concerned.