Parameters for tool life optimisation with respect to face milling

Abstract

Initially a review of the process of face milling is undertaken, including an outline of the methods of tool failure and ways of overcoming some of these failures. A practical study is made of the tool life of indexable tungsten carbide inserts when being used to face mill a medium carbon steel. Tool life in this context is expressed in terms of the flankwear on the cutting tool. Techniques are established for the method of conducting the cutting tests and the procedure for measuring the flankwear. A face mill containing a Single insert is mounted directly in the main spindle of the milling machine and the down-cut and up-cut milling mode is obtained by varying the height of the testpiece, relative to the cutter, so that the main cutting force is always acting downwards towards the machine table. Using conventional cutting speeds and feeds, standard positive rake and negative rake inserts are examined when up-cut and down-cut milling. A range of chamfer angles and chamfer widths are ground on standard inserts and the effects on tool life investigated. It was found that chamfering the positive rake inserts improved the tool life and that an optimum chamfer angle of 15° exists. The 15° angle improves the tool life from a few seconds to 45-40 minutes. The cutting forces produced by the standard and modified inserts are studied, to ensure that changing the geometry of the inserts does not significantly alter the cutting forces.