| Selective Laser Sintering(SLS),an additive manufacturing technique,has gained widespread adoption in the engineering industry in recent years because of the characteristics of forming parts with arbitrary complex geometric shapes,no additional support,rich application of different materials,and high material utilization through the volume of different materials.However,the current SLS molding equipment is mostly industrial grade equipment,which is expensive,and the powder feeding mode used is mainly single powder feeding or powder feeding.Due to the restriction of powder feeding mechanism,it is difficult to form a stable and controllable chemical gradient between layers,resulting in the production of molded parts with limited performance,which may not meet the demands of complex working conditions.Therefore,there is an urgent need for a SLS molding equipment that can realize multi-material gradient molding.In light of the extant issues with industrial equipment,this paper has developed and produced a hybrid powder-fed non-metallic laser sintering molding apparatus that utilizes an STM32 microcontroller as its control core.Based on this equipment,the discrete unit method and experiments were utilized to investigate the impact of powder laying process parameters on powder laying quality.Based on the principle of SLS equipment forming and the design idea of up-down mixed powder feeding and gradient forming,the overall design scheme of the mechanical system of mixed powder feeding nonmetallic laser sintering forming equipment was determined.Based on the analysis of the demand for powder supply and the study of the structure of powder supply,a powder feeding system which can realize alternating up and down powder supply is designed.In order to solve the problem of low efficiency of powder spreading,a two-roll powder spreading system was designed.By analyzing the significance of powder bed preheating and the influencing factors on temperature uniformity,we have completed the design of a mask preheating device and determined its optimal installation height through experimentation.A laser system composed of laser,vibroscope and lens is developed by using the scanning optical path structure of scanning vibroscope + "F-θ" lens focusing.Based on the three modules of powder feeding,powder laying,preheating and laser,the functions and design objectives of each module control system are analyzed,and the hardware control structure of "PC +STM32 microcontroller" is determined.The hardware circuit system of normal operation of controller,stepper motor driving,heating tube preheating,laser output of specific power,galvanometer scanning deflection,serial communication of up and down machine is designed.Based on the hardware design of the device control system,Keil u Vision5 and STLINK/V2 emulator serve as the software development environment and tools for accomplishing research and design of the device control system software.Firstly,an upper computer software that integrates slicing and printing control is developed.Secondly,we have designed a motion control program for the acceleration and deceleration of stepper motors,a PID temperature closed-loop control program for heating tubes,an algorithm for laser output power specific to each application,and a motion control program for scanning deflection mirrors.Through discrete element numerical simulation and experimentation,the powder laying process was studied,and the influence of powder roller radius,translational velocity,and rotation velocity on powder laying quality was analyzed.Based on the simulation results,a set of optimal parameters for the powder laying process were obtained and validated through experimentation.This provides a guiding basis for equipment structure parameter settings. |
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