Enhancement of geometric accuracy via an intermediate geometrical feedback scheme

Abstract

To enhance the geometric accuracy of a machined part, both the static and dynamic errors present in the NC machining procedure should be handled in some manner. This paper presents systematic compensation methods for these errors based on an intermediate geometrical feedback scheme. In the new scheme, the machined part is: (1) measured (on the machine), (2) compared with the CAD model, and (3) the toolpath is corrected repeatedly until the predefined geometric accuracy is obtained. The "execution-and-correction" method can be viewed as an interative part programming procedure, and it can be directly applied for the repetitive machining environment. This paper presents theories and algorithms for the scheme, including: (1) a method for enhancing the accuracy of CNC machine tools by the analytic volumetric error model, (2) a method for utilizing the machine tools for on-machine inspection, and (3) a machining error compensation method by path modification. The validity and effectiveness of the developed method was tested via contour cutting experiments with a vertical three-axis CNC milling machine.