SLM成形中粉末铺展行为的动态数值模拟

Numerical simulation of laid powder based on selective laser melting

激光选区熔化中,粉床的成形会显著影响后续的工艺及最终产品的质量.试验采用离散元法(DEM),对SLM成形过程中的粉末铺展行为以及成形质量进行了动态数值模拟,从致密度和均匀性两方面研究了粉床质量的影响因素.研究结果表明,铺粉速度对粉床质量的影响很明显.铺粉速度、铺粉角度、刮板间隙高度、粉末粒度均对改善粉床的平均致密度和均匀性有着重要影响.铺粉速度越小,粉床质量越高,同时工作效率也越低.随着刮板间隙高度的增加,粉床致密度增大,粉床均匀性降到一个较低的值;粉床致密度随铺粉角度的增大而增大,然后减少,整个粉床的结构均匀性也有类似的变化趋势.增大粉末粒径会导致粉床致密度和粉床结构的均匀性降低.当铺粉速度0.1 m/s,刮板间隙高度90μm,铺粉角度15°,粉末粒径15μm时,粉床成形质量最优.

In laser selective melting,the forming of powder bed will significantly affect the subsequent process and the quality of final products.In this paper,the dynamic numerical simulation of powder spreading behavior and forming quality in SLM forming process is carried out by using discrete element method(DEM).The influencing factors of powder bed quality are studied from two aspects of density and uniformity.The results show that the effect of powder spreading speed on the quality of powder bed is obvious.The powder spreading speed,powder spreading angle,scraper clearance height and powder particle size all have an important influence on improving the average density and uniformity of the powder bed.The lower the powder spreading speed,the higher the quality of powder bed and the lower the working efficiency.With the increase of the clearance height of the scraper,the density of the powder bed increases and the uniformity of the powder bed decreases to a lower value.The density of powder bed increases with the increase of powder laying angle,and then decreases.The structural uniformity of the whole powder bed also has a similar change trend.Increasing the particle size of powder will reduce the density of powder bed and the uniformity of powder bed structure.The powder spreading speed is 0.1 m/s,the clearance height of scraper is 90μm.The powder spreading angle is 15°,and the powder particle size is 15μm,the powder bed forming quality is the best.The research results of this paper will provide a valuable reference for the formation of high-quality powder bed in SLM process.