Process planning for rotational parts using the generalized travelling salesman problem

Process planning for rotational parts can be described as deciding on the order of machining the various features. However, this problem entails more details since each feature, hypothetically, can be machined by a left- or a right-hand tool, and in many cases, the parts can be chucked from either end. Another complicating factor is that some features require machining from both directions (with both left- and right-hand tools) and some can be machined by either tool. Thus, the process planning problem for rotational parts decides on the order of machining the various features, the chucking direction and the tool to be used for each feature. Every time the part is chucked or to a lesser extent when the tool direction is changed, the accuracy of the feature is compromised and productivity is reduced due to time spent on non-cutting operations. A good process plan, therefore, should consider the productivity as well as the overall accuracy of the part. This paper presents an algorithmic graph-theoretic approach towards determining the optimal process plan such that the part's overall accuracy is maximized, given the accuracy of the machine and the features tolerances. In particular, we describe the process-planning problem as a generalized travelling salesman problem and then use known procedures to solve the problem. This solution minimizes the overall impact of rechucking operations and tool changes on the process accuracy. Therefore, in addition to the improved precision, the process plan results in faster and more efficient operations.