Apparatus for measuring positional movement of a numerically controlled machine tool

摘要

An apparatus for measuring the positional movement of a movable workpiece of a numerically controlled machine tool. The apparatus comprises an incremental linear measuring system arranged along the path of movement of the movable workpiece, a rotary measuring system, mechanically coupled to a drive of the movable workpiece, and means within the computer control of the machine tool to relate the resulting measurements from the two systems to one another. The measuring resolution of the rotary measuring system is substantially greater than that of the incremental linear measuring system such that if the rotary measuring system is subordinated to the incremental linear measuring system, the machine tool can achieve greater control accuracy with respect to stopping and positioning the workpiece. The apparatus can also be configured to measure characteristics of the machine tool such as spindle pitch, spindle pitch error, and backlash and correct any control inaccuracies accordingly.