| Machine tools are the essential processing equipment in the process of mechanical manufacturing. For the vertical drilling and milling machine tools which have only one direction of movement, the key is the accuracy of positioning and clamping of the workpiece during processing. So, it can make the correct size. Fixture, as we said, is the tooling, which can accurately clamping and positioning the work piece in the process of machining. It can also make the machining process faster and more convenient.According to the using features, the types of fixture can be divided into general fixture, special fixture, adjustable fixture and combination fixture. For some parts with multiple holes in space, the common three- axis machine tool could make use of the some special fixture and combination fixture to complete a series of machining processes. But, when finished one hole, the fixture would be demounted and the part will be reset to make sure the next process is good. Therefore, the use of special fixture will greatly reduce the processing efficiency and economic costs. So, the use of special fixture would greatly reduce the processing efficiency and economic costs. Similarly, the five coordinate machine tools or more advanced machine tools could complete the processing of the work piece, but the cost would be high. Therefore, it was significant to design a fixture platform with multi rotation and tilt and could be controlled by advanced control technology. As is known to all, the parallel mechanism has been favored by many scholars because of the advantages of large bearing capacity, simple structure, easy processing and control. The original intention of the design was the fixture can drive the work piece to rotate and tilt. The combination of the parallel mechanism would achieve what we expected.Firstly, in the first chapter introduced the background and significance of the research on the parallel fixture platform. Then, it showed the development status of three degree of freedom(3-DOF) parallel mechanism in some aspects at home and abroad. Also, the kinematics and the control research status would be included.Secondly, in the second chapter showed the application occasion of the parallel fixture platform as one part of the three coordinate axis vertical milling machine in this paper. Then, it highlighted the design of the parallel fixture platform and the importance of conFig.uration and put some examples. Then, it led to the concept and method of the design 3-DOF parallel fixture platform. We made the Sketching, did the math of the DOF and totally analyzed all parts of the mechanism. Meanwhile, calculate and select the type of motor, drive, parallel connection plate, screws. Then, check the intensity of the guide rods. At the end of the paper, the prototype had been made out.Thirdly, in the third and fourth chapter analyzed the kinematics characteristics of the 3-DOF parallel mechanism in Matlab and Adams. Established the mathematical model and the inverse solution was programmed by MATLAB, and the displacement image of the three sliding blocks is obtained by using the method of spatial geometry. Imported the three-dimensional model into ADAMS, set the parameters, and the displacement map of the three sliding blocks is also obtained to verify the correctness of the inverse kinematics model. Meanwhile, making use of the curve to form the spline curve, which could lead the slider move to get the forward kinematics.Lastly, in the fifth chapter, the control system was designed and the prototype was assembled, and the experiment was carried out. Set a series of parameters in LinuxCNC and use G code to control the mechanism to reach the purpose movement in this paper. It wad easily introduced the wiring method of the motor, drive, parallel connection plate. A simple vertical milling machine was made and combined with the parallel fixture platform to closely relate to practical applications. |
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