SLS 시스템의 최적 설계 및 소결 공정 특성에 관한 연구

Abstract

Recently, in order rapid growth of high-tech and customer diverse need, rapid manufacturing of product or modification make accessory effect such as a competitive price, the reduction of the new product development time, etc. Due to SFF(Solid Freeform Fabrication) system of using various process and materials, demand is being continuously increase. For this reason, the multi-functional SFF systems are actively being studied into the real manufacturing process, which are used not only for fabricating a solid freeform 3D CAD files but also for scanning a 3D object rapidly and precisely. Especially, A SFF system using selective laser sintering (SLS) is currently recognized as a leading process and SLS extends the application to machinery and automobiles due to the various materials employed. SLS process creates 3D object, layer-by-layer, using powder materials with heat generated by a CO2 laser. With SLS process, prototypes have been produced with various uses of thermoplastic, metal composite and ceramic composite powder. SLS system is consist of various elemental technique such as the powder laminate for control of build room and feed room position, control of roller velocity, powder sintering for control of temperature, scan path generation etc. SLS system is that the surface quality of prototypes and the processing time are significantly affected by several parameters such as laser power, laser beam size, heat temperature and laminate thickness. In order to develop a more elaborate and rapid system for fabricating compared to existing SLS, this study developments a SLS system and sintering process. It contains a 3-axis dynamic focusing scanner system for maintaining uniform laser beam size everywhere instead of the f lens used in commercial SLS. In this study, experiments were performed to evaluate the effect of various laser scan parameters and fabrication parameters on sintering process and to fabricate the various 3D objects using a PA-12 starting material. The results of optimized process are able to reduce process time and improve fabrication accuracy and efficiency. Also, this study suggest a scan path generation method to fabricate more 3D objects quickly and precisely. The results of experiment showed excellent sintering capabilities through the proposed methods. This study also evaluated the characteristics of fabricated sample by optimized sintering conditions such as the sintering density, the surface roughness, microstructure, chemical and thermal properties, etc.