Study On The Open Multi-functional Laser-processing NC System

Content: The common numeric control (NC) system that is widely applied in current laser processing both domestically and internationally, is a kind of specialized and closed system. Due to its limitation in expansion and high price, the system cannot meet the requirements of high flexibility and low cost in today's processing industry. Therefore, research on NC technology in recent years has been focused more and more on the open NC system with outstanding flexibility and low cost, which also represents the developing direction of laser-processing NC technology.This thesis aims at developing an open, multi-functional laser-processing NC system, partially for the Experiment and Research Base of Tsinghua Laser Processing Research Center. The system is expected to simultaneously operate several processing modes (including laser cutting, laser surface modification and laser welding), and demonstrate features of openness, multi-function, intelligent function and high-speed processing. The focus of the paper is on the design of NC system, its components and structure, and the study of some key NC technologies.After thorough comparison and analysis on the current open NC processing technologies in China and western countries, and on the basis of several feasible plans, the "Principle & Subordinate Design" based on industrial-PC and PMAC control-card is finally adopted. The design is open through its standardized ISA-line and Windows software, providing an excellent framework for the whole NC system.A mechanical platform based on the simultaneous movement of the four axes (X, Y, Z-translation and C-revolving) is developed in the system, which is suitable for the simultaneous movement of laser cutting, laser surface modification and laser welding. The author also adopts the leading technology in today's software development and designs a software-mainline-based software frame, by using the COM-tech realizationunder Windows, which provides a software base for the high-speed input of laser-processing data.CPLD technology is applied in the design of mouthpiece boards, and the hardware logic is programmed in VHDL language. Thus, the laser processing NC system can update and expand its mouthpiece logic through on-line programming at any time, and achieve high flexibility.In the paper, an intelligent optimal calculation method for laser cutting assistant-path, based on genetic calculation, is also suggested. The method can automatically optimize the location of initiating point and start-cutting point and the sequence of closing object cutting. It can not only improve the quality of laser cutting but also guarantee the shortest laser-off path, which will improve the cutting efficiency. . Due to the application of fixed laser beam and moving workpieces, the machine has a large-quality moving part. As a result, the maximum acceleration is limited, which hinders the speed and the steadiness in laser processing of curves. By using the Position-Velocity-Time mode of PMAC and cubic parameter spline moving, the problem in low-acceleration processing is successfully solved in this paper.