In-process sensing of tool wear and process states using a cylindrical displacement sensor in hard turning

摘要

A cylindrical capacitance-type spindle displacement sensor was developed and its effectiveness as a system for monitoring cutting conditions during hard turning was tested in this research. The sensor was installed between the face of the spindle cover and the chucking element, and measured pure radial motion of the spindle under conditions of roundness error at the measured surface. To prove the effectiveness of the developed system, hard-turning tests using ceramic inserts and with tool steel as the workpiece were conducted. The workpiece was hardened up to 65 Rc. The variations in pure radial motion of the spindle were measured during the cutting tests. The signals from the sensor showed the same pattern of cutting force variations from the tool dynamometer due to the progress of tool wear. As the flank wear of the ceramic tool increased, both the static component of the cutting forces and the centre shift of the spindle orbit increased. Results from the research showed that the developed sensor could be utilized as an effective and cheap on-line sensing device to monitor cutting conditions and tool performance in the unmanned machining centre.