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Shaping of IPS empress 2 framework ceramic by grinding

 
: Schmidt, C.; Weigl, P.

Höland, W. ; Deutsche Glastechnische Gesellschaft -DGG-, Frankfurt/Main:
International Symposium on Crystallization in Glasses and Liquids 2000. Proceedings : July 9 - 12, 2000, Vaduz, Principality of Liechtenstein
Frankfurt/Main: Verlag der Dt. Glastechnischen Ges., 2000 (Glass Science and Technology 73 C1)
ISBN: 3-921089-27-1
S.362-365
International Symposium on Crystallization in Glasses and Liquids <2000, Vaduz>
Englisch
Konferenzbeitrag
Fraunhofer IPT ()
machining; jig grinding; IPS Empress 2

Abstract
A long life time behaviour of ceramic denture 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 to machine dental ceramics. Using ceramic materials for an automatic production of ceramic dentures by CAD/CAM is a challenge, because a lot of technological, medical and optical demands have to be considered. The IPS Empress 2 framework ceramic keeps most of it. This study shows possibilities to machine this ceramic with economical parameters. 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. Result of the wear test was low tool wear. With one tool you are able to machine eight occlusal surfaces by roughing and finishing. One occlusal surface takes about 60 minutes machining time. Recommended parameters for roughing are middle diamond grain sized tools (D107), cutting speed v(c) = 4,2 m/s, feed rate v(ft) = 1000 mm/min, depth of cut a(e) = 0,06 mm, width of contact a(p) = 0,8 and for finishing ultra fine diamond grain sized tools (D46), cutting speed v(c) = 4,2 m/s, feed rate v(ft) = 100 mm/min, depth of cut a(e) = 0,02 mm, width of contact a(p) = 0,8 mm.

: http://publica.fraunhofer.de/dokumente/B-64749.html