Study Of Galvanometric Scan And Control System In Selective Laser Sintering

Galvanometric laser scan technology is widely used in rapid prototyping as core component for its advantage of fast scan speed and high precise. Selective Laser Sintering is an important branch of rapid prototyping, and is increaingly applied for its advantage of fast prototyping speed and various materials. Selective Laser Sintering is related to CAD/CAM, CNC, laser, new materials and accurate servo system techniques. This paper studied the general design of scan system, the design of scan control card, the calibration of scan image and the automatic control and monitoring of the whole system in Selective Laser Sintering equipment.This paper investigated the related theory of galvanometric laser scan system, and analysed the affection of laser performance to the scan quality of the galvanometric laser scan system, and analysed the request of scanner using in Selective Laser Sintering system with various work field. Through deeply studying the scan model of the galvanometric laser scan system with F-theta objective and the galvanometric laser scan system with dynamic focus, designed and realized the galvanometric laser scan system based on PC with taking into account the performance and costs of the Selective Laser Sintering system. This scan system uses a type of soft IC, which realizes the transform module, the interpolation module, the image calibration module and interruption data processing module of the scan system in PC.Based on this scan system, one type of low cost Selective Laser Sintering system with this scanner using F-theta lens or dynamics focus was realized.The distortion of scan image using galvanometric scanner was analysed, and the calibration algorithm for image distortion was realized based on the mathematics model of the galvanometric scanner. When the galvanometric scanner is used in the Selective Laser Sintering system, the image distortion will be so serious that the precision of the image can not be calibrated well with the work field increasing, The galvanometric scanner with F-theta objective is usually used in the Selective Laser Sintering system with a work field less than 350mmx350mm; Because of the obvious distortion, the image must be reshaped before calibrating the precision of the image. The mathematics model of the galvanometric scanner with dynamic focus is an accurate model, the image distortion of which is very small, and the main errors include the error of mechanical installation and the error of laser path, so the precision of the image can be calibrated by a multi-point calibration method.The system architecture, hardware architecture and driver software of the scan control card for galvanometric scanner were investigated, and a set of scan control system was realized, which carried on the model transform, path interpolation and calibration arithmetic in PC and output data through a piece of general I/O card having interrupt functions. The interrupt cycle of the general I/O card is at ns level, and the system realizes the control of the galvanometric scanner through interrupt response. Based on the use of general I/O card, a new scan control card was accomplished, which used FPGA component to carry out part of data processing. The new scan control card could realize the control of the galvanometric scanner and optimized the system resource.The motion control system and preheating temperature control system of Selective Laser Sintering system were investigated, and according to the feature of Selective Laser Sintering system, a sophisticated automatic process suitable for Selective Laser Sintering system was implemented. To give full consideration to the fault and interference of the Selective Laser Sintering system, a sophisticated operational monitoring method was implemented to insure the stably and safty function of the Selective Laser Sintering sytem.Thus, this paper studied the related theory of galvanometric scanner system, and developed the galvanometric scanner with F-theta objective and the galvanometric scanner with dynamic focus suitable for Selective Laser Sintering system through solving above problems. The research results will promote development of Selective Laser Sintering technology in China, and it will benefit the spread and exploitation of Selective Laser Sintering technology.