Influence of exit angle and tool nose geometry on burr formation in face milling operations

Abstract

One of the more important burrs produced in a face milling operation is the burr formed on the exit edge in the cutting direction. This burr is present over the full length of the exit edge, and under certain cutting conditions is relatively large in size, strongly attached to the workpiece, and presents a strong configuration, features that make it difficult to remove and consequently increases the cost of the component. This paper is concerned with the influence of the exit angle and tool nose geometry on the formation of this burr for both finishing and roughing conditions (small and large depths of cut respectively), with a medium carbon steel. The results show that four different types of burr can be produced on the exit edge, namely the tear, curly, rubbing and wavy burrs. The exit angle and the tool nose geometry have a significant influence on the formation and characteristics of the burr formed on the exit edge. Under finishing conditions, exit angles greater than 90° and large tool nose radii facilitate the formation of large primary burrs. Under roughing conditions, on the contrary, the exit angle affects the type of burr produced on the exit edge, whereas the tool nose geometry only influences the burr size. The formation of primary and secondary burrs is mainly determined by the chip flow angle ρ; primary (wavy) burrs usually form for ρ > ρt (where the transition chip flow angle ρt ≈ 42°, in this case) and secondary (tear) burrs for r < rt.