Abstract:

PA12 parts were prepared using a multi?jet?fusion （MJF） 3D printing technology， and the effect of construction orientation on the forming accuracy and mechanical properties of PA12 parts were investigated. The results indicated that the size accuracy was always positive deviation when the position size was the width direction. There is no obvious change law at different forming angles. Compared to the width direction， the size accuracy in thickness direction and the length direction increased with the forming angle， indicating a more obvious change law. The mechanical properties of parts presented a similar influence of forming angle with the elongation rate. When the forming angle increased from 0 ° to 45 °， the tensile strength and elongation rate of parts gradually decreased. The tensile strength and elongation rate increased significantly after the forming angle was greater than 45 °. The trend in the induced density change was consistent with the mechanical properties. According to comprehensive analysis， the size accuracy of the parts reaches an optimal level when the molding angle was 45 °. The forming direction for optimal mechanical performance was parallel to the x?y plane direction. Under this condition， the PA12 parts obtain average tensile strength of 50.95 N/mm²， average elongation of 37.02 %， a forming angle of 0 ° for the highest density， and an average density of 99.311 %. The MJF technology was more efficient compared to the traditional 3D printing technology. This study offers a theoretical and experimental foundation for the mass production of high?performance and high?precision nylon parts.

Key words: additive manufacturing, multi?jet melting, polyamide 12, dimensional accuracy, mechanical property