Patent attributes
According to a machining device for machining a conductive workpiece (W) by a conductive (T), when the tool (T) contacts the workpiece (W) in machining, there is formed a closed-circuit (C) connecting the tool (T), the workpiece (W), a brush (315), a conductor (311), a main spindle housing (12), a main spindle (11) and again the tool (T in that order. Alternating-current is inducted to the closed-circuit (C) by a high-frequency generator (314) and an exciting coil (312). As a contact state between the tool (T) and the workpiece (W), impedance of the closed-circuit (C) is changed and then the alternating-current is changed, so that induction current is generated at a detector coil (313), thus monitoring and controlling the contact state by way of the induction current. Since a light contact state can constantly be maintained in machining according to a monitoring condition including a light/heavy contact-determining threshold, cutting resistance will not increase, thereby preventing damage on the tool (T) and deterioration in machining accuracy.
