Forming Principle of 3D P Process

- Jan 03, 2019 -

According to the process requirement, a series of layers are obtained by discrete layering of the CAD three-dimensional model. According to the contour information of these layers, the powder laying device lays powder layer by layer, and the sprinkler sprays binder droplets to solidify layer by layer selectively, forming the contours of each section, and gradually and orderly superimposing into three-dimensional entities. However, the 3D P process is formed by agglutination of powders, and the formed parts have porous structure. This structure will make the strength of the parts lower. The formed parts need to be densified by post-processing strengthening technology to improve their strength. The post-processing technology (such as high temperature sintering, hot isostatic pressing) will make the volume of the parts shrink seriously. Therefore, it is the focus and difficulty of current research to densify parts or dies formed by three-dimensional printing without obvious volume shrinkage by adopting appropriate post-processing strengthening technology. At present, the research on three-dimensional printing of metal powder mainly focuses on the control and optimization of forming process parameters, the improvement of post-processing and strengthening process, etc. Its purpose is to solve the problem of low precision and strength of parts. High temperature sintering and hot isostatic pressing are the main densification processes used in metal powder 3D P forming. Studies based on infiltration process have also been reported. After densification, the densification of parts can reach 98%, or even complete densification. However, the shrinkage rate of the densified parts is very large, which makes the final size of the parts deviate greatly and makes it difficult to obtain near-net products. This is the key to hinder the industrial application of rapid manufacturing of metal parts by 3D P.