Proceedings PaperUse Of The Laser Interferometer For Position Feedback
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Machine-tool manufacturers have traditionally used position-feedback devices such as resolvers, encoders, Inductosyns, etc, to provide slide-displacement data to the control servo system. The location of the cutting tool and workpiece are thereby inferred by measuring a secondary characteristic such as the angle of the motor drive shaft or lead screw. Undesirable features of this technique arise from unstable elements that are outside the measurement loop as well as from inherent accuracy considerations. The laser interferometer position-measuring system offers an accuracy that is unsurpassed by conventional feedback systems; and, while it is more expensive, it should represent only a mall fraction of the total cost of a precision, numerically controlled machine tool. Also, it is frequently possible to measure more closely the location of the cutting tool and workpiece from a common reference, thereby avoiding some potential thermal-instability problems.