In order to reduce the number of tedious operations affected to the operators, to improve their working conditions by reducing dangerous operations and to improve quality consistency of manufactured work pieces, many industrials chose to automatize different kinds of processes. Grinding process is one of those processes that represented a serious problem. Removal of Excess material, surfacing and creating complex shapes in workpieces are dangerous grinding operations. Those time consuming operations are affected to skilled operators to do manually. They become a bigger problem when the size of the work pieces is very large, which is the case for a large number of forged parts. One solution for this problem is robotization. In this paper, the use of an active end effector capable of compensating the grinding contact force needed for grinding operations is investigated.

First, the robotized grinding system is modeled. As a case study, rounded corner grinding operation of large parallelepipedal parts is chosen. The round is located on the superior surface of the parallelepiped work piece. The grinding wheel is at a constant angle α compared to the grinded surface. To calculate the grinding force, a simplified grinding model is used. The used grinding model for the chosen grinding application is that of Persoons and Vanherck, which relates the grinding force to the material removal rate.

Then, the grinding path is described by defining the succession of points where the center of the grinding disc must pass. The grinding operation is done in two steps in order to reduce the needed time. First in the roughing step, the material removal rate is maximized. The area of the contact surface between the grinding wheel and the workpiece is consequently maximized taking into consideration the maximum grinding force. The workpiece corner is grinded in multiple layers that have the same thickness. Each layer is broken down by several passes of the grinding wheel. Knowing the maximum contact surface, the maximum cut depth is deduced. The grinding wheel in each layer of the roughing step is placed between two passes of the previous layer. Taking into consideration the maximum cut depth already calculated. Therefore, the objective of the grinding program, for the first step, is to obtain in each grinding pass the same contact area to maximize the MRR. The second step is finishing operation, in which the quality of the final surface is more important than the material removal rate. The quality of the grinded surface is determined by the roughness and shape defect. Two different methods were compared. The first finishing method consists of placing the second pass in the same radius as the previous one but at a slightly bigger angle θ in relation to the vertical axis. This angle depends on the wanted surface quality. The second finishing method consists of placing the next pass between the two last pass at the same radius, in order to grind the peaks of the surface. It is shown in this paper that the choice of the finishing strategy depends only on the wanted surface quality Ra.

Finally, the effect of varying the grinding contact force is studied. It was shown that increasing this force can significantly reduce the number of grinding passes and therefore reduces the grinding time. For this reason, determining the proper contact force is of great importance.