Tolerance analysis and allocation of special machine tool for manufacturing globoidal cams

In order to produce a special machine tool for manufacturing high-quality globoidal cams, this paper presents a systematic approach for tolerance analysis and tolerance allocation for the special machine tool. Based on the differential geometry and conjugate theory, the machined surface and the surface deviation of a globoidal cam are derived with the help of a VS software. The sensitivity model and the worst-case method are applied to analyze the effects of machine tool errors on the machined surface deviation. Manufacture easiness index which can evaluate the level of manufacture difficulty and can also indirectly imply manufacture cost is proposed. Then, the optimization problems are formulated to the maximize manufacture easiness index subject to quality target of cam surface and manufacture constraints. The optimization results are obtained by using MATLAB implementation of linear programming. To confirm the optimization results, they are applied as a guideline to design and manufacture this special machine tool. After that, a globoidal cam is manufactured on this machine tool and measured on a coordinate measuring machine (CMM). The measuring results demonstrate the effectiveness of the proposed approach.