SLS forming of typical complex parts in rapid investment casting

Based on the rule of dimensional error transfer and reverse engineering, the 3D digital scanning of complex parts after one wax immersion was carried out. According to the structural characteristics of complex parts, zgscan717 plus intelligent hand-held 3D scanner, which is a non-contact measuring device, is used to detect the 3D information data of complex parts Control software optimizes the point cloud data of 3D digital model, compares the data with the original part data, determines the size error of each part, calculates the size error of the part, verifies the existing size error transfer law, determines the final size error compensation way, and finally prepares the qualified SLS prototype.

The typical complex parts used are diffuser impeller as shown in the figure. According to the size of the parts, the casting dimension tolerance grade is cT4 ~ CT6. The maximum outer diameter of the part is 262.99mm, the height is 142.85mm, and the volume is 1823.32cm3. The diffuser has 8 blades evenly distributed on the upper part and 16 blades evenly distributed on the side. The diffuser casting belongs to a typical thin-wall rotary part (the minimum wall thickness of the upper blade is 1.88mm and the minimum wall thickness of the side blade is 2.40mm).

It is found that the strength of SLS prototype is really strong and the size of the sample changes due to the effect of wax liquid after a wax soaking treatment. In order to improve the surface quality of wax pattern, a layer of wax layer is uniformly adhered to the part after one-time wax immersion. At the same time, in order to facilitate the data detection process, the diffuser part after one-time wax immersion is selected for three-dimensional information data detection. Therefore, sls300 rapid prototyping equipment was used to conduct SLS prototype firing under laser power of 30W, powder layer thickness of 0.14mm, scanning speed of 3000mm / s, scanning spacing of 0.31mm and preheating temperature of 95 ℃. After fully cooling and removing the floating powder on the surface, the part shall be treated after wax dipping at 65 ℃ for one time. After cooling to room temperature, the residual wax drops on the surface shall be removed.

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