Research On A Novel 2 DOF Fast Tool Servo Actuator For Ultra-precision Diamond Turning

Precision and ultra-precision manufacturing technology have great influence on the developments of national defence industry and high technique, therefore, many countries pay great attention to its developments. In recent years, There is growing need for effective ways to manufacture micro components as well as micro features on a large workpiece surface that have applications in the fields of optics, MEMS, semiconductors and micro-molding of plastics. In order to obtain high accuracy and a fine surface, position control of machine tool has become the main concern to achieve the high precision position control. The fast tool servo, which is an independently operated positioning device, would have a small rang but high bandwidth and accuracy compared to the conventional mechanism. In this thesis, a novel nano-metric precision 2 DOF fast tool servo actuator for micro-structured surface ultra-precision machining is developed. The main contents are presented as follows:1. IntroductionAt first, the current development of precision and ultra-precision manufacturing technology are introduced. The configuration and principle of fast tool servo for precision machining and micro features manufacturing are also presented.2. Basic TheoryThis part introduces the basic theory of piezoelectric effect, particularly gives a detail description on piezoelectric stack, about its structure and features. It also introduced the principle and influential factor of ultra-precision machining technique. At the same time the mechanical, physical, chemical and metallic features of single-crystal diamond are presented. Found a solid academic foundation for designing the precision actuator.3. Structure Design of the 2 DOF fast tool servo actuatorFirst, gives a detail introduction about flexure hinge and fingers out its design principles. Analyze the mechanics characteristic of the flexure hinge, which was the key element of the 2 DOF precision actuator, and gains their stiffness equations, analyses the related factors affecting the stiffness.Then propose the project that transform the linear displacement of the piezoelectric stack into rotary motion via torsion flexure hinge, and based on the method develope the piezoelectric 2 DOF fast tool servo actuator.It explain the working process of actuator in detail , and analyse the working principle of every parts . Analyses the effect of preload on flexure hinge, and the result shows that the output of flexure hinge has nothing to do with preload but has a relationship with the stiffness. Also forms a dynamic model of the driving part and gains the transmit function. Gain the structure's numerical solution of displacement, stress and frequency response via finite element software HyperMesh.4. ExperimentsFirst, introduces the devices used in the experiments, testifies the features of piezoelectric stack and the stiffness of flexure hinges.Then design the experimental system to test the actuator's working performance The experiment results is shown as following:The minimum beeline displacement is 8nm when the cutting depth is 10μm and the main cutting force is approximately 0.1N, the minimum rotary angle (rotary resolution) was 0.27μrad when the actuating voltage was 0.1V; the maximum rotary angle output is 955μrad when the actuator was without load.Moreover via experimental method, the thesis studies the performance of the working stability, repetitive positioning accuracy, the capability of bearing load and the dynamics performance of the servo actuator. The testing results showed that the piezoelectric fast tool servo actuator has good performance.5. ConclusionMakes a conclusion to the whole thesis, and gives some suggestion for future development.