Abstract
In recent years, demands for high-precision machining are increasing in the manufacturing of precision dies and molds, optical parts, and high-precision electrical parts. In such machining, it is a critical issue to minimize the relative position errors between the tool tip and the workpiece, since they are copied to the machined surface. The objective of this research is to investigate a methodology to measure and control relative position errors between the tool tip and workpiece, which is referred to as tool-workpiece closed-loop control. Especially, this paper covers the flat surface machining on XY plane. For this purpose, a three-axis vertical machine with the measuring system was developed. Three linear axes are driven by ball screws. Additionally, for the relative position control, the Z-axis has a fine motion mechanism driven by a piezoelectric actuator. In order to measure the relative displacement, a laser displacement sensor is installed near the cutting tool, and an artifact is installed near the work piece. By using control terminology, this measurement system is referred to as a relative-position observer. By the tool-workpiece full-closed loop control , the straightness errors are reduced to about &pousmn;0.4 μm /90 mm.
