In-situ axis error detection module

The in-situ Axis Error Detection Module (ISAMOD) is a multi-beam laser measurement system that when coupled with outputs from a machine’s linear and rotary encoders can partially monitor geometric errors of a linear axis. Three of these modules mounted onto one axis of a machining centre can deduce the linear position, yaw, and pitch errors of that axis. The purpose of this combination of modules is to enable the detection of adverse play in the mechanics of the machine axes for condition monitoring, failure, remaining life predictions, and to increase the accuracy of refurbished machines in a low cost, low maintenance, unobtrusive manner. The primary operation of the ISAMOD is based on the high-speed measurement of relative change in position of parts of the machine axes during dynamic operation. ISAMOD performs its primary operation by utilising a high-powered diode based Michelson’s interferometer with an internal phase shift. This source is then multiplexed across the three modules to remove wavelength variation, increasing accuracy for pitch and yaw measurement. Linear positioning accuracy is increased by controlling the diode source temperature. Secondly, ISAMOD is design to be small enough to fit under the axis guards and perform constant in-situ measurement of many common linear axes. By incorporating the ISAMOD system in this way, machine downtime needed for axis calibration is reduced. Furthermore, maintenance and full geometric calibration with additional systems, which are inherently more intrusive to production, can be more carefully scheduled, based upon the condition of the axis given by the ISAMOD system.