In view of the influence of different post-treatment on the surface quality of the specimen, considering the low surface strength of the wax pattern, in order to prevent the surface scratch of the specimen caused by the contact contact method, the optical non-contact measurement method is selected to measure the specimen. Zygo newview 9000 white light interferometer is used for observation and test, as shown in Figure 1.
The surface quality of the SLS rapid investment casting prototype, the specimen after the first wax immersion and the specimen after the second wax immersion were measured by taking the marked points as the sampling points. The specific measurement results are shown in Figure 3.
Figure 3 is the surface roughness test results. Through the analysis of different treatment steps, it can be seen that the post-treatment has a great influence on the surface roughness of the specimen. It can be seen from Fig. 3 (a) that the surface roughness values of the test planes ① and ② of SLS rapid investment casting prototype specimens are larger than that of plane ③, because the test planes ① and ② are used as laser sintering surfaces, so their surface roughness values are larger, while the surface roughness values of the test planes ③ are smaller due to the adhesion of floating powder due to the effect of sub sintering phenomenon. The average surface roughness of SLS prototype is 33.928 μ M. It can be seen from Fig. 3 (b): after one wax immersion, the surface roughness of the three test points has little difference, mainly because at 65 ℃ wax temperature, the specimen has the smallest size deviation, and a certain thickness of wax layer is adhered on the surface, thus improving its surface quality. The average surface roughness of the specimen after one wax immersion is 25.137 μ M. It can be seen from Fig. 3 (c) that the surface quality of the specimen is further improved after the secondary wax immersion at 75 ℃. The average surface roughness of the specimen after the secondary wax immersion is 2.203 μ m, which is 93.5% higher than that of the SLS prototype specimen.