Enhanced CNC lathe capability by addition of a grinding spindle

Abstract

CNC grinding machines are widely used to obtain a good surface finish and tight tolerances. However, these machines are expensive, therefore manufacturers are considering adding a grinding spindle, interchangeable with a boring bar, to a turning lathe. To facilitate this, complex software is required because the programmer must control the whole surface of the grinding wheel not just the tool or cutter tip, as in turning or milling. This paper presents a general algorithm to simplify the grinding programme. The programmer will use this algorithm to create a subroutine suitable for the machine. The subroutine may then be used for all grinding operations. The programmer will need only to describe the contour of each workpiece, as for a CNC lathe program, in a separate small program. The algorithm has been applied to a hollow spindle lathe equipped with Sinumeric 840 C numerical control, and several gun barrels were turned and ground using the proposed approach. Satisfactory results were obtained.