| OCR Text |
Show 1 of GARI. The plans generated seem to be very sensitive to the weights associat d with the rules. This is undesirable because the numerical weights are assign d somewhat arbitrarily, to reflect qualitative preferences [15]. 3.4.2 MetCAPP MetCAPP is a computer aided process planning system which has been developed by Metcut Research Associates Inc. in 1988 [10]. Like many other process planning systems, MetCAPP uses features to describe parts to be machined. MetCAPP combines database of tools available, modules to make recommendations on data selections, and decision-rule-based expert machining module used to standardize machining methods and practices. From features described by users, MetCAPP recommends operation plan including time estimates. To generate the operation plan, user has to identify the order of the features to be produced. Then, tools are selected for the operation sequence for each given machined part feature and cutting speed and feed rate for each cut are recommended. Details of the implementation methods including rule based expert machining module are not available, but important drawbacks can be found. Like GARI, M~CAPP lacks a complete solid model. Another important shortcoming is that user has to specify the order of features to be machined in order to get the operation plan. This means that the operation plan generated by MetCAPP may not be efficient because the user may provide inefficient order of features. Furthermore, the final operation plan is formed simply by concatenating the sets of opertions for the features in the order specified by the user. In other words, operations requiring same tool are not grouped. This causes extra time for changing tools, and thus user has to reorder the operation sequence in the operation plan to generate an efficient operation plan. |
