Machinability of IPS Empress?2 Framework Ceramic: Potential for Ceramic Dentures

摘要

Using ceramic materials for an automatic production of ceramic dentures by CAD/CAM is a challenge, because many technological, medical, and optical demands must be considered. The IPS Empress?2 framework ceramic meets most of them. This study shows the possibilities for machining this ceramic with economical parameters. The long life-time requirement for ceramic dentures requires a ductile machined surface to avoid the well-known subsurface damages of brittle materials caused by machining. Slow and rapid damage propagation begins at break outs and cracks, and limits life-time significantly. Therefore, ductile machined surfaces are an important demand for machine dental ceramics. The machining tests were performed with various parameters such as tool grain size and feed speed. Denture ceramics were machined by jig grinding on a 5-axis CNC milling machine (Maho HGF 500) with a high-speed spindle up to 120,000 rpm. The results of the wear test indicate low tool wear. With one tool, you can machine eight occlusal surfaces including roughing and finishing. One occlusal surface takes about 60 mm machining time. Recommended parameters for roughing are middle diamond grain size (D107), cutting speed V_C valence 4.7 m/s, feed speed V_(ft) valence 1000 mm/mm, depth of cut a_e valence 0.06 mm, width of contact a_p valence 0.8 mm, and for finishing ultra fine diamond grain size (D46), cutting speed V_C valence 4.7 m/s, feed speed v_c valence 100mm/min, depth of cut a_e valence 0.02 mm, width of contact a_p valence 0.8 mm. The results of the machining tests give a reference for using IPS Empress?2 framework ceramic in CAD/CAM systems.