Proceedings of the 7 th International Conference Coatings in Manufacturing Engineering, 1-3 October 2008, Chalkidiki, Greece Edited by: K.-D. Bouzakis, Fr.-W. Bach, B. Denkena, M. Geiger, Published by: Laboratory for Machine Tools and Manufacturing Engineering (ΕΕΔΜ), Aristoteles University of Thessaloniki and of the Fraunhofer Project Center Coatings in Manufacturing (PCCM), a joint initiative by Fraunhofer-Gesellschaft and Centre for Research and Technology Hellas 173 EFFECT OF THE CUTTING EDGE SHAPE ON THE PERFORMANCE OF COATED CEMENTED CARBIDED INSERTS K.-D. Bouzakis 1,3 , S. Gerardis 1,3 , G. Katirtzoglou 1,3 , A. Bouzakis 1 , E. Lili 1,3 , S. Makrimallakis 1,3 , R. Cremer 2,3 , H.-G. Fuss 2,3 1. Laboratory for Machine Tools and Manufacturing Engineering, Mechanical Engineering Department, Aristoteles University of Thessaloniki,Thessaloniki, Hellas 2. CemeCon AG, Würselen, Germany 3. Fraunhofer, Project Center Coatings in Manufacturing, A joint initiative by the Fraunhofer and the Centre for Research and Technology Hellas (CERTH) ABSTRACT In the present paper, the effect of the coated cutting edge shape on the tool milling performance is described. According to the actual cutting edge profile, three groups of coated cemented carbides inserts with an AlTiN PVD film without treatment (as dep.) as well as with slight (S.G.) or intensive (I.G.) cutting edge rounding were ex- amined. The cutting edge geometry was determined by confocal white light scan- ning, while the film thickness on the tool flank and rake were registered, by micro cratering tests combined with confocal measurements. The impact resistance and corresponding fatigue properties versus the impact temperature were detected by impact tests. The cutting performance of the inserts of the various groups, was in- vestigated in peripheral milling, of hardened steel 42CrMo4 QT. The obtained re- sults were explained by FEM calculations of the material removal process enabling the determination of the developed stresses and temperature distributions in the cut- ting edge region. In these calculations, the exact coating thickness on the tools’ flank and rake were taken into account. The slight decrease of the coating stresses and on the other hand the enlargement of the cutting temperature in the case of a cutting inserts with slight or intense rounded cutting edge, lead to cutting edge equivalent radius increase and thus to lower loadings of the coating material. Fur- thermore at enhanced film properties in the fatigue endangered transient cutting edge region during the critical tool entry into the workpiece were achieved. Due to the reduction of coating thickness at the cutting edge, the heat transfer and thus the cutting temperature is increased. In this way the cutting performance can be drasti- cally deteriorated. KEYWORDS: Cutting edge geometry, Milling, Undeformed chip length, Cutting speed 1. INTRODUCTION Sharp cutting edges of milling cutters with small diameters, are often rounded by grinding. In this way the cutting edge becomes more stable and the cutting performance can be increased. The investigation of the related wear phenomena is of crucial importance towards explaining the coating failure and adjusting the coated tools’ geometry according to the films’ material proper- ties. Figure 1 illustrates the grinding process on sharp cutting edge of a milling cutter. In this way three categories based on the cutting edge roundness has been produced. As the cutting edge region becomes more rounded the stress are evenly distributed on the transient area between