Sensor-less micro-tool contact detection for ultra-precision machine tools utilizing the disturbance observer technique

When molds for micro products are repaired, micromachining is typically required after the welding or cladding process. The contact position of the tool to the cladded material needs to be set before micromachining. However, precise setting of the tool to the workpiece is a technically difficult operation that requires manual adjustment and the introduction of external sensors. This paper proposes an observer-based automatic detection method for micro tool contact. An ultra-precision machine tool driven by a linear motor was utilized to demonstrate the effectiveness of the proposed sensor-less tool contact detection method. Experimental results showed that the observer-based tool detection method can detect submicron-level contact, which cannot be achieved manually.