Shrinkage Error Analysis in Selective Laser Sintering Hybrid Milling

Selective laser sintering hybrid milling (SHM) is an advanced manufacturing process that combines the advantages of both metal powder bed fusion and milling. Using this technology, extremely complex products can be fabricated with high accuracy and reasonable surface quality. SHM has enormous potential in the application of mold fabrication; molds with free-form inner cooling channels can be produced with this technology. The key feature of this technology is that milling is conducted not only after, but also during the forming process. However, this leads to the issue that although machined layers of products have a high level of accuracy without thermal deformation, the addition of new layers causes the materials to undergo shrinkage and deformations to occur on their machined layers. The dimensional error due to shrinkage significantly affects to the accuracy of SHM process; therefore, a completely understanding of the formation error due to shrinkage is highly important in developing efficient solutions. In this study, shrinkage deformation is observed in detail through the results of simulation using finite element analysis. Three shrinkage rules and the unclamping effect are proposed to completely explain the shrinkage error shape in SHM. Finally, an experiment is conducted to confirm the final result of shrinkage.