MRR-Based Productivity Decisions in Hard Machining

Machining procedures applied in the machining industry have been developing fast due to up-to-date tool materials, new machine-tool structures and automation solutions. This is why today a part’s surface can be machined by more than one procedure having even completely different features. The potential procedures of a certain problem (machining a surface) are those that fulfill the accuracy and surface quality requirements specified in the drawing. The time parameters, the surface rate or the material removal rate can be parameters suitable for comparative analysis and ranking of the selected procedures. In this paper five machining procedures were chosen for machining hardened surfaces. Optimum cutting data, which can be recommended for real plant application as they fulfill the specified roughness and accuracy requirements of the part surfaces, were determined from machining experiments. Considering these data the machining times, operation times and the practical parameter of the material removal rate introduced by us were calculated. This differs from the widely applied theoretical value for material removal rate because it does not reflect just the theoretical time necessary for material removal but takes into account the actual manufacturing/machining times necessary for the machining of the component/surface. The analyzed surfaces are the various diameter and length bore holes of hardened gear wheels produced in large scale. Their efficiency parameters were calculated when the surfaces are machined by traditional bore grinding, hard turning (two procedure versions) and a combined procedure (two procedure versions). On the basis of these data a ranking was determined among the procedures.