Optimization of material removal rate for orthogonal cutting with vibration limits

Márta Janka Reith, Gábor Stépán
2012 Periodica Polytechnica: Mechanical Engineering  
Besides growing accuracy requirements for cut parts the maximisation of productivity has still an important role in industry. One possible measure for productivity in cutting processes is the material removal rate. This study deals with the optimisation of the material removal rate considering the bounds set by vibrations through an analitical approach. The damping ratio region was determined, for which the identified local optima with respect to the maximal material removal rate hold.
more » ... rate hold. Introduction An optimal machining strategy always depends on the determined objective function. Efficiency can be measured according to several criteria. These can be: cost effectiveness, minimal/optimal time, optimal usage of capacity, surface quality of the workpiece, tolerances and accuracy, minimal specific energy consumption and lifetime. A further measure can be productivity, which is closely connected to the material removal rate. Besides well constructed objective functions, there are several conditions an engineer has to deal with when the task is to develop an optimal machining strategy. One group of restricting conditions are the quality requirements for the surface of a machined workpiece and the accuracy. Furthermore, there exist bounds for parameters belonging to each part of the system, the technology, the machine, the tool, the chuck and the workpiece. There are also factors, which cannot be determined from catalogues yet, for example the boundaries of chatter-free (stable) regions of a machining process. The surface quality of the workpiece is highly effected by vibrations occurring on machine tools. Due to the direct contact between tool and workpiece, the motion of the tool directly shapes the workpiece surface. There is a variety of reasons causing vibrations, which can be handled by means of active or passive vibration elimination methods, but dealing with chatter vibrations is a far more complicated issue. The source of these self-excited vibrations is, on the one hand, the regenerative effect caused by the feedback between subsequent cuts modulating the chip thickness [1, 2]. On the other hand, mode coupling can cause self-excited vibrations during machining, but for the investigations in this study, only the regenerative effect for the chip thickness is taken into consideration, since chatter caused by the mode coupling effect occurs later for most machining cases [3] . The target of the presented study is to present an analytical approach for the maximisation of the material removal rate (MRR) taking into account the bounds set by vibrations. One of the most important objectives in industry nowadays is maximising productivity, since it is directly connected to machining costs. Productivity can be measured via the MRR. For milling, Budak and Tekeli [4] showed a method for increasing Optimization of material removal rate 91 2012 56 2
doi:10.3311/pp.me.2012-2.03 fatcat:4thco66tkjbjdcezz4iuh76kuy