An Enhanced DFM Model for Shaper Cutters

Abstract

This paper presents a systematic CAD/CAM based geometric modelling technique for enhancing the manufacturing accuracy of general straight-tooth shaper cutters. The proposed modelling technique systematically computes and improves on the shape of general shaper cutters using a five-step procedure. In the first modelling step, the significant geometric parameters of shaper cutters which including tooth profile, rake and clearance angles, offsets, and backlash are estimated using criteria associated with the practical requirements and the theory of gearing, differential geometry, and motion theory. In the second modelling step, the precise cutting-edge curve model of the shaper cutter is constructed. The theoretical involute or cycloidal cutting-edge curve on the plane perpendicular to the motion axis of the shaper cutter is first computed and is then projected onto the conic surface of the shaper cutter which has both the rake and the clearance angles. In the third modelling step, the convoluted sectional profile of the disk-shaped generating cutter required for producing the cutting-edge profile is established using the theory of gearing and the relative motion relationship between the grinder and the cutter in the manufacturing process. In the fourth modelling step, a simple procedure to obtain the profile shift coefficient of the shaper cutters from various given process parameters is presented. Shaper cutters of various shapes can thus be designed and produced. In the last modelling step, a practical working example for producing the precise disk-shaped generating cutter and associated shaper cutter is presented to illustrate the effectiveness of the proposed modelling approach. The results of numerical modelling indicate that the proposed approach is systematic, accurate and reliable for producing shaper cutters of various shapes.