Study On Real-time Scanning Strategy Of Selective Laser Melting Based On Temperature Field Detection

Selective laser melting(SLM)is a metal additive manufacturing technology with great application prospects,especially suitable for forming complex structural parts with high degree of freedom and high precision.However,due to its single-point high-energy input process characteristics,it is difficult to avoid local heat accumulation,large temperature gradients and even cause warpage,cracking and other problems in the forming process,which restricts the development of this technology.During the SLM forming process,laser scanning path planning and energy input control are effective measures to balance the temperature field of the forming layer,avoid stress concentration,and prevent deformation cracking.The traditional path planning method and laser process parameters are set in advance before SLM forming,so it is difficult to cope with individual differences in SLM equipment operating conditions and heat accumulation in the forming process of complex parts.To this end,this paper proposes a real-time scanning strategy of selective laser melting based on the temperature field detection of the forming layer,including real-time path planning method and laser power control strategy.The conclusions are as follows:The real-time path planning method is to divide the area to be scanned and store relevant path information,and perform online planning of the scanning sequence based on the real-time temperature uniformity of each area during the scanning process.The temperature of each area can be adjusted during the laser scanning process to form a uniform layer temperature field;the laser power control strategy reduces the initial value of the laser power layer by layer to compensate for the heat accumulation,and the dual-mode power control algorithm in parallel with steady state control and fuzzy control regulates the laser power in real time during forming to stabilize the scanning area temperature field to further improve the uniformity of the temperature field of the formed layer.And through abnormal monitoring for defect prediction and detection error handling,to ensure the stability and reliability of the system operation.In this paper,based on the existing additive manufacturing software architecture of the research group,a new data processing and control process is constructed,and the SLM process control software based on temperature field detection is designed.The software includes two parts: process planning and control system.The thread synchronization model realizes the multi-thread collaborative function of real-time temperature acquisitionplanning control,adding a real-time path planning method to the process planning,adding temperature acquisition and laser power control modules to the control system,and replacing the laser scanning and motion control modules to meet equipment hardware configuration requirements,and ensure the scalability and adaptability of the software.Using SLM to form 316 L stainless steel parts,the temperature field and residual stress distribution of the parts are analyzed.The research results show that the proposed real-time path planning method can significantly improve the temperature uniformity of the forming layer and slow down the local stress concentration and residual stress of the formed parts;laser power control strategy can effectively alleviate the heat accumulation of the forming layer and the temperature instability of the scanning area;and can predict the forming defects according to the abnormal temperature distribution.This study provides a reference for the algorithm and software platform for further improving the quality of SLM forming.