Research On Optical Radiation Monitoring Technology Of Ceramic Material Laser Selective Melting Pool

The rapid development of selective laser melting technology provides a new method for forming complex ceramic pieces.However,because the ceramic materials have special physical properties of low laser absorptivity,high melting point,high brittleness,the forming process will produce high temperature gradient and prone to warping deformation and crack,SLM forming is very difficult,it is urgent to break through the technological process and the optimum technological parameters suitable for the ceramic SLM forming.Besides,when manufacturing complex geometry or large volume parts,the processing time needed is longer.If we can't evaluate the quality of the forming process online,it will lead to the continuation of forming defects.The behavior of melt pool is the main factor determining the forming quality,monitoring and analyzing the behavior of melt pool is an important method to master the characteristics of SLM forming process and optimize the forming process parameters.In order to monitor the thermal behavior of melt pool and improve the quality of ceramic SLM forming,this paper studies the technology of optical radiation monitoring for ceramic SLM from aspects of monitoring system design and melt pool thermal behavior analysis.A melt pool light radiation monitoring system,consisting of hardware and software system,is established for the SLM forming process.By near infrared filter technology and photodiode detection circuit,the data of melt pool light intensity in the forming process are obtained.In order to improve the detection precision of melt pool,a photodiode multi-detection head detection system is designed.As the change of the melt pool light intensity in the different forming positions of laser desorption can't be visualized by the time domain signal,the mapping algorithm is proposed to model the data of the melt pool.Based on the melt pool optical radiation monitoring system to carry out a series of experiments,the influences of different process parameters and boundary conditions on the thermal behavior of the melt pool were obtained by studying the melt pool data,which provided technical support for the development of the ceramic SLM process.In order to study the quality defects of ceramic SLM forming and improve the forming quality,the relationship between the change of melt pool state and the forming quality was obtained by analyzing the change of the characteristic state of the melt pool data,and the feasibility of defect monitoring was explored.