INVESTIGATION INTO TURN-MILLING PROCESS

Abstract

A new process for machining of rotationally symmetrical workpieces can be achieved, if the rotation of the workpiece is combined with the motion of a rotating milling cutter, i.e. turn-milling process. In the mean time the cutter is fed longitudinally, as in turning, parallel to the workpiece axis. The advantages of this new process include machining of high strength materials, machining of large and heavy workpieces, production of short chips and long tool life. Problems of unbalance arising when turning large and heavy workpieces, especially at high cutting speeds, are solved in turn-milling by rotating the workpiece only few revolutions per minute and obtaining the main cutting speed from the rotation of the tool. Turn-milling is the suitable machining process for complete machining i.e. performing all the necessary machining operations, turning, drilling, milling, grinding and thread tapping, from roughing to finishing on a single machine and at a single setting. Advantages of complete machining include reduction of lead time, increasing accuracy by reducing multi set-ups, increasing metal removal rate and reduction of production costs.

The industrial applications of the process include machining of the following components, aircraft landing gear leg, calendar rolls for paper industry, turbines and valves for power plants and injection moulding screws for the plastic industry.

In this research, a theoretical study of the kinematics of the process has been carried out. The results indicate that the surface quality could be improved if either the . speed ratio or the number of teeth increase. Moreover, the productivity may increase if \ the workpiece speed, the depth of cut, the tool diameter increase or the speed ratio, or the number of teeth decrease.