DRY HIGH SPEED MILLING AS A NEW MACHINING TECHNOLOGY OF CERAMICSFOR BIOMEDICAL AND OTHER APPLICATIONS

摘要

Ceramics are the first choice for orthopaedic,dental and other biomedical applications.Because of the processes used,the conventional production of ceramic parts is moreover limitedto materials that are not optimal from a medical point of view.Further critical issues forbiomedical applications are cooling lubricants and polishing materials used for machining theceramics.Absorption into the surface of the machined ceramic parts makes them not neutral forthe human body so they can cause allergic reactions or diseases.The developed dry,high speedmilling of ceramics (Ceramill)presented in this work solves this problem.The method and aprototype machine tool for 3D treatment with the implementation of advanced controls,CAD-CAM coupling,high speed spindle,the dry process and the dedicated new tools have beendeveloped and approved in field tests.Work pieces with dimensions till 200×400×400 mm hasbeen constructed.Suitable geometries and coatings for new milling tools have been determined.The machining tests were performed with various parameters such as diamond coating thicknessand composition.The trials have been performed with aluminium oxide,zirconium oxide andsilicon nitride.Ceramill leads to accurately finished products with tolerances of the order ofmagnitude of 1 micron and surface roughness of 0.2 microns.First measurements of the Weibullfactor for silicon nitride show an encouraging value of 57 by a load of 628 Mpa.A first modelfor the process based on the mechanistic approach has been established on the MatLab platform.