Abstract
This paper is devoted to enhance the accuracy of five-axis machine tools. Although five-axis CNC machine tools are widely used in mold and die industry, relevant works in the field of the enhancement of accuracy of five-axis machine tools are sparse. The reason is on one hand the interaction of linear and rotary axes complicates the relationship between the sources of errors and the final errors at the tooltip and makes it difficult to find a suitable compensation method. On the other hand, the increasing kinematical complexity makes it very difficult to measure the overall positioning errors.In this paper, a new measurement device, the probe-ball, is presented which can be used to measure directly the overall position errors of five-axis machine tools. To explain the nature of the probe-ball error measurement, a theoretical model is derived with the HTM method. After setting all measured errors in the error model, a reduced error model is defined which describes the influence of each unknown and not measurable link error on the overall position errors. The unknown link errors can be estimated based on the probe-ball measured data using the least square estimation method. Based on the fully known error model, a new error compensation strategy using linear function is proposed. This compensation method is simple and implemented in real-time. The test results show the positioning accuracy of the five-axis machine tool can be improved dramatically.