Testing a method for evaluating the performance of coatings on end mills in semi-industrial conditions
¹Institute of Technology, Estonian University of Life Sciences, Kreutzwaldi 56, EE51014 Tartu, Estonia; *Correspondence: Tonu.Leemet@emu.ee 2 Institute of Physics, University of Tartu, Riia 142, EE51014 Tartu, Estonia 3Department of Materials Engineering, Faculty of Mechanical Engineering, Tallinn University of Technology, Ehitajate tee 5, EE19086 Tallinn, Estonia
Milling remains as one of the most versatile machining operation in manufacturing. Machine tools with several axis of movement and precise numerical controls are able to manufacture complex geometries for medical implants, parts needed in space technology etc. The quality of the workpiece and the cost of manufacturing are influenced by many factors, tool selection being one with considerable impact. Depending on the specific type of milling operation and the material of the billet, the coating of the cutting tool can have a significant influence to quality and cost of the process. In this study an attempt is made to develop a methodology for relatively simple but effective means for evaluating the suitability of a coating for a particular milling operation. Flank wear width is generally recognized as the key indicator for tool life criteria. Relatively complex geometry of the end mill makes the flank wear measurements somewhat difficult. In practice several other indication of tool wear are used: changes in the spectra and volume level of the sound emitted from the cutting process, shape and color of the chips, quality of the manufactured surface and the presence of the burrs. In this work the flank wear measurements by optical measurements are analyzed and reasoned, additional information is found by scanning electron microscopy. Three industrial PVD coatings – TiAlN, naCo and nACro were tested.