EXPERIMENTAL INVESTIGATION OF MICRO-MILLING ACCURACY USING ON-MACHINE MEASUREMENT SYSTEM

In this paper, we proposed an error decomposition method, in which some major error components can be experimentally estimated using an on-machine measurement (OMM) system. Unlike the conventional machining, the geometric error of a micro-tool, i.e., the deviation of the effective tool diameter from a nominal value, becomes a dominant factor affecting the machining accuracy. The error stems from both the tool fabrication error and the dynamic runout of the spindle system under high rpm. An on-machine measurement system based on a non-contact confocal laser sensor was developed that can accurately and efficiently acquire the effective tool diameter. To compensate the error due to the tool geometric error, the effective tool diameter was used to replace the nominal tool diameter to generate the tool path. The experimental results showed that the tool geometric error contributes over 50% to the total machining error. After compensation, the machining accuracy was significantly improved. The machine contour error has negligible influence on the dimension error of the machined feature, but it affects the form error, such as circularity of a machined hole. The process induced surface location errors were estimated from both experiments and model simulations, and good match was achieved.