Study On Flow Distribution Characteristics Of Gas Flow System In A Selective Laser Melting Equipment

The flow of inert gas can remove byproducts generated during selective laser melting(SLM)processing,which is the key to improving the quality of parts.However,the uneven flow field inside the processing chamber limits the ability of inert gas removal.In order to study the uniform distribution characteristics of the internal flow field in the machining chamber,this article takes the gas path system of a certain model of SLM equipment as the research object,and uses CFD numerical simulation method to analyze the influence of factors such as the structure and operating conditions of the gas circulation inlet on the uniformity of the machining chamber flow field.By establishing a theoretical model of flow distribution,it is proposed to add a guide plate structure to the gas circulation inlet and optimize its structure,so that the inert gas flow is evenly distributed in the machining chamber,Improve the cleaning ability of the gas system.Firstly,analyze the removal process of by-products,construct a particle transport model,and establish a three-dimensional flow numerical model and flow performance evaluation index applicable to this article.Three typical air intake schemes have been established based on different inlet sizes.The influence of inlet size and gas flow velocity on flow uniformity was analyzed through CFD numerical simulation method.The results indicate that the area of the air circulation inlet is the main influencing factor on the distribution of the chamber flow field.By arranging a large-sized circulation inlet,the velocity deviation index is reduced from 0.3335 to 0.1538.When the flow rate of the upper air circulation inlet decreases to 0.2m/s,the airflow uniformity above the processing surface is optimal.Secondly,the flow state in the machining chamber was characterized by velocity uniformity,and the influence of the structural parameters of the air circulation inlet on the uniformity of the flow field was analyzed.The results showed that the uneven distribution of flow in the machining chamber was caused by the excessively fast flow velocity in the central area of the air circulation inlet.By reducing the baffle aperture to 5mm and arranging double baffles,the velocity deviation index on the machining surface was reduced by 48.62%and 73.93%,respectively.Finally,a fluid distribution model for the orifice outflow and expansion structure inside the air circulation inlet was established with the goal of optimizing airflow uniformity.It was proposed to add a guide plate structure inside the air circulation inlet and explore the influence of the number,shape,length,orifice length,and inlet shape of the guide plates on flow uniformity using CFD numerical simulation method.By arranging a 50 mm long 6-layer fan shaped guide plate inside the inlet and transforming the inlet shape into a triangle,The overall uniformity of the lower air circulation inlet can be improved to 92.48%,which is 10.53% higher than the original equipment.Build an SLM equipment experimental platform and use the optimized airflow system for smoke removal experiments.The results show that the optimized airflow system has stronger smoke purification ability,reduces the accumulation of smoke in the processing chamber,and verifies the rationality of the airflow design.