Development Of A New Apparatus For Three-dimensional Elliptical Vibration Cutting

Optical crystal and other brittle materials, hard ferrite steel materials are widelyused for precision parts and molds, but these materials in the cutting process cancause serious diamond tool wear, deterioration of the machined surface quality andreduce machining accuracy, so the current method of cutting is difficult to obtain asatisfactory machined surface. Three-dimensional elliptical vibration cutting (EVC)what is generally considered the most potential to improve the difficult materials’machinability as a processing methods can suppress the wear of diamond tool, reducethe cutting force effectively, reduce cutting heat. In order to take advantage of thethree-dimensional EVC method effectively to improve the machinability of materialsdifficult to machine, the development of a high-performance three-dimensional EVCapparatus and control system are key technologies. However, the existingthree-dimensional EVC apparatus have some problems in eliminating movementbetween the coupling and parameters adjustment in each axis of three-dimensionalEVC. Therefore, this dissertation will focus on the development of a newthree-dimensional EVC apparatus and control system, and by theoretical analysis andsimulation, the offline performance testing and cutting experiments.In this paper, double row symmetrical flexible hinge mechanism oriented thethree independence movement, three motion axes are arranged perpendicular to eachother, flexible hinge mechanism is designed to be integrated to avoid the mainstructure of assembly errors. The PICMA type piezoelectric stack drive the flexiblehinge mechanism directly, the Microsense TMII5300-type capacitive displacement sensor detects the displacement feedback. According to the layout to optimize flexiblehinge mechanism, the main dimensions of the components are design variables, stress,frequency and elastic restoring force as the constraints, the minimum reduce therequired parasitic motion in the plane as the objective function, and ultimately drawthe corresponding parameters optimize the value of obtained this optimizationparameters stiffness, frequency and maximum stress values.The finite element based on the optimization of the design results validate theanalysis and the actual stiffness test. Analyzes the stiffness of the three directions: Xto8.5034N/μm, Y to12.3365N/μm, Z to9.5265N/μm, the first natural frequency:1236Hz. The test is derived to test the stiffness of the X, Y and Z three directions,respectively9.5017N/μm,10.8918N/μm and13.0674N/μm, system resonantfrequency is248Hz. Since the analysis meshing process is not precise enough,assembly and other reasons, analysis and testing errors exist, but little impact, able tomeet the test requirements.In order to better grasp the system characteristics, in this paper, system dynamicsmodeling to draw the transfer function of each as the third-order parameter model.MATLAB System Identification Toolbox offline parameter identification to obtain amore accurate recognition results, X, Y, and Z directions recognize the goodness of fitwere98.77%,98.66%,99.26%, respectively. Based on PMAC+PC works PIDfeedforward feedback control system design, trial and error tuning PID parametersand other parameters, the closed-loop performance tests by device structure, threedirections disturbance values were less than5%, verify that the three-directioncoupling; elliptical trajectory fitting at different frequencies, come to work in thefrequency of30Hz, more regular oval, able to meet the test requirements.In order to verify the workability of the apparatus, the paper selectellipsometric parameters cutting operating frequency as30Hz, three-directionretardation as pi/2, the amplitude of the three directions X, Y, Z respectively as6μm,8μm,3μm. Select brass and silicon as planar cutting materials, to verify the workability of the apparatus planar processing,3D EVC superiority in difficult tomachine materials is verified by comparing the test. While surface cutting, machinemotion with EVC apparatus vibration synthetic the elliptical path, rotary encodercollect spindle rotation angle information to form the trigger signal, both to ensure thesynchronization of the movement. The sine wave surface cutting results of6061aluminum verify the apparatus enables the surface machining.