Precision design and numerical control machining of tapered ball-end milling cutters

The paper presents a systematic modelling approach for precision design and numerical control (NC) machining of the tapered ball-end milling (TBEM) cutter that has emerged as a powerful tool for mould-making industries. The major contribution of this work is to produce a complete cutting edge that was conventionally neglected or oversimplified near the ending portion interfacing with the tapered ball end. In order to comply suitably with the requirement for a specific rotating speed, both radial and axial cutting speeds are carefully derived by using a given helical angle defined as the angle between the cutting edge and the revolving axis. Both projected profiles, one normal to the revolving axis and the other tangential to the groove, are used to produce precision sectional profiles of the grinding wheel. In compliance with maximal sectional radius of the taper, the profile of the groove section and the feeding speed of the grinding wheel are computed in sequence. By means of a two-axis NC machine, the shape of the TBEM cutter that possesses a nearly constant helical angle can be systematically designed and produced. With a slightly remedial grinding procedure at the ball end, the dimensional accuracy of the groove and the cutting edge of the TBEM cutter can be well controlled.