Development of compliant mechanisms for real-time machine tool accuracy enhancement using dual-servo principle

Abstract

The quality of machined precision components is defined by the degree of accuracy of the machine tools used in its manufacturing process. So every process and its corresponding machine tool, needs to maintain the high degree of accuracy and precision in order to realize the end product with the desired surface quality. The cost of manufacturing and maintenance of such high precision tools defines the cost of the finished product. Hence the product cost and machine tools accuracy has its own tradeoffs. Real-time error compensation technique is well applauded for its efficiency in improving the machine tools quality without an increase in its cost. But the accuracy of such compensation technique depends on the resolution of the machine tool system. Hence, to effectively improve the accuracy of the machine tool without an increase in initial investment, a real-time compensation based on auxiliary axis using proven precision compliant mechanism will be effective. Diamond turning machines (DTM) are widely used in high precision optics and energy sectors due to its single step final finishing process to produce mirror-finish surfaces. Though the capabilities of using the DTM are manyfolds, still its cost is sky-high. To improve the surface integrity of machined components in DTM and to reduce the initial cost of machine a dual servo based real-time compensation system is developed and the outcome of the implementation are presented in this thesis. Single axis fine tool servo (FiTS) system is developed, analyzed and implemented in the DTM for improving the surface quality. Mirror finished flat-faces are produced with xii combined real-time geometric and kinematic error compensation and pre-compensation techniques. Novel efficient compliant mechanism module called ?Inverted Double Parallelogram? was introduced and the performance study of the new design revealed that for both axial and transverse loading, parasitic error, which is one of the important aspect in deciding the accuracy of the compliant mechanism is reduced significantly. The accuracy of a basic DTM is determined by its two motion slides (X and Z). Hence, a dual axis complainant mechanism is required to compensate the errors of the axes. Effective actuator isolation and avoidance of cross-axis error is critical in designing a dual axis complaint mechanism. A dual axis compliant, planar mechanism is developed and successfully implemented in real-time dual servo error compensation of DTM during contour machining operation. The design, development, analysis and implementation of the single and dual axis FiTS systems on DTM, together with the findings on the improvements of the machined workpiece quality are presented in this thesis.