Proceedings of COBEM 2009 20th International Congress of Mechanical Engineering Copyright © 2009 by ABCM November 15-20, 2009, Gramado, RS, Brazil INFLUENCE OF THE EXTERNAL THREADING PROCESS AT HIGH SPEED CUTTING ON TURNING OF DENTAL IMPLANTS Rodolfo da Silva Manera, rodolfoman@aluno.feis.unesp.br Alessandro Roger Rodrigues, roger@mat.feis.unesp.br Hidekasu Matsumoto, hidekasu@dem.feis.unesp.br Juno Gallego, gallego@dem.feis.unesp.br Engineering Faculty of Ilha Solteira - FEIS/UNESP, Av. Brasil Centro, 56 - Zip Code 15385-000 - Ilha Solteira-SP - Brazil Abstract. This work evaluated the effect of cutting speed on machinability and surface integrity of titanium dental implants (ASTM F67 degree 4). Chip formation, tool wear, workpiece microhardness and thread surface quality were investigated. TiNAl coated carbide tools and abundant cutting fluid were used in external threading process (CNC lathe). The results indicated alterations on workpiece microhardness generated by different cutting speeds. The chip formation depended on cutting speed reaching the segmentation for higher cutting speed. Images obtained by Scanning Electron Microscopy (SEM) revealed that increase on cutting speed was prejudicial for thread surface quality and threading tool due to wear and adherence. The cutting temperature estimated by a thermadynamic model reached 1283°C. Keywords: dental implants, high speed cutting, external threading, surface integrity, machinability. 1. INTRODUCTION The wide use of titanium and its alloys reflects its good physical and mechanical properties in service. The high ratio between strength and weight is one of the most valuable characteristics in its industrial selection. Non-alloyed titanium is commonly used where there are strong corrosive agents and the need for fatigue strength (Wang, 2000). Although this material’s excellent applications characteristics, Shaw (1984) classifies titanium as a low machinability material, because of the high temperatures achieved in cutting and poor deformation and shear metallurgical characteristics in machining. In medical use, commercially pure titanium, generally used in dental implants manufacturing, can be classified according to ASTM F67 standard in four degrees of purity in its chemical composition. The increasing use of titanium and its alloys in implants manufacturing, either orthodontic or orthopedic ones, are due to the simultaneous presence of the excellent biocompatibility (already proved by Williams, 1981), the high mechanical and corrosion strength, and relative low density of these materials. The osseointegration rate of the implants is directly related to their surface quality. Several researches show that surface roughness affects the bone integration ratio e the bio-mechanical fastening (Gemelli et al, 2007). In the case of the dental implants, the machining process responsible for the generation of the thread fillet is the most influent agent in the surface quality and in the sub-surface integrity. This paper presents a quantitative and qualitative evaluation of the surface integrity of titanium dental implants by microhardness measures and thread fillets’ images obtained by SEM. Besides that, the machinability is evaluated when studying the chip formation mechanism, the tool wear and cutting temperature determination. 2. MATERIALS AND METHODS Performed by “IMPLALIFE – Medical-Dental Products Industry”, the manufacture of specimen (commercial dental implants), with dimensions of ∅5 x 15 mm and external thread M5 x 0.8 mm, has been done with Titanium ASTM F67 degree 4, machined with a turning machine CNC STAR®, model SR-20RII, with power of 2.2 kW. The machining was used external thread tool ISCAR® 16 ER 0.80 ISO IC 908 (coated carbide with TiNAl) and cutting fluid ECOCUT 910 (FUCHS®) in abundance. Cutting parameters are show in Tab. 1. Table 1. Cutting parameters used to manufacture the specimens. Cutting speed [m/min] pitch [mm/rot] Depth of cut [μm] ** 19 and 70 0.8 * 100 * Thread with double entry. ** Deph of cutting applied in each pitch of the thread. The metallographic preparation of specimens began with the slitting of the samples, using a diamond abrasive disk and application of lubricating and coolant fluid in abundance. After sectioning, the specimens were built-in in polyester resin, sanding with sizes 320, 400, 600, 1000 and 1500, and polished with alumina 0.03 μm. The measures of