Development Of CNC System For Microstructure Machine Tool Based On PMAC

Microstructure functional surface which have particular micro-topological structures are widely used in the field of optical system because of their special properties, such as optical characteristics. Nowadays, the main method for high efficiency mass production of microstructure optical functional surface components is replication techniques. However, during the copy process of the microstructure optical components, the machining quality of microstructure surface molds have decisive influence on the performance of final product. Therefore, the research and development of machining tool and CNC system for microstructure optical functional components have great significance.Considering manufacturing processes for microstructure dense array of light guide plate mold, a tool device driven by piezoelectric actuator was mounted on the machine, pushing the diamond tool forth and back at high frequency. This paper develops a computer numerical control (CNC) system for the machine tool. The hardware platform based on IPC (Industrial PC) and PMAC (Programmable Multi-Axis Controller) is designed for the CNC system.To begin with, according to the processing requirements of microstructure dense array, establishing the overall layout of the machine tool, selecting hardware of machining system. Design the tool device and analysis of its driving principle. The electric control system of the computer numerical control is built, and the connection of the input and output signals is determined. The friendly and simply operated interactive software of CNC system is developed by the method of modularization based on Qt4.8. The key problems of CNC system software and the implementation ways of functional modules are discussed in depth.Next, the on-machine measurement system of microstructure dense array based on Balser and OpenCV is developed, and it achieves continuous collection and image saving. By using standard sample, the detection system is calibrated. Preprocessing the collected images, and the 9*9 template subpixel edge detection method based on cubic splines interpolation is presented. Fitting circles to a contour by least square method, to obtain the pixel size of the diameter of circular contour, and the actual size of the diameter is calculated by the calibration coefficient.Finally, in order to improve steady state characteristics and dynamic characteristics of control system, it is tuned through adjusting PID parameters, velocity, acceleration, and friction feed-forward parameters. The system positioning error of each axis was obtained by laser interferometer, and accomplished the position error compensation. As a result, the positioning accuracy of machine tools was improved. Where, the positioning error of X axis in the 24.57μm range at the initial time, which became into 2.155μm after compensation. In this paper, the arrangement mode of the micro dot array is introduced. Using the developed CNC system to process the four types of microstructure dense array, and the microstructure was detected by white light interferometer. The machining experimental results are consistent with the actual requirements, which show that the developed CNC system is applicable for the machining of microstructures in ultra-precision machine.In conclusion, this paper has obtained the research results, such as hardware platform construction, man-machine interface design, open CNC system development, machine vision detection, control system PID adjustment and verification experiments. These studies have reference value to the development of CNC system for microstructures.