Identifying Similar Parts for Assisting Cost Estimation of Prismatic Machined Parts

This paper presents a method for identifying those parts in a database that are similar to a given query part to be machined and hence can be potentially used as a basis for estimating the machining cost of the query part. We utilize projected feature vectors consisting of feature access directions, feature types, and feature volumes as a basis for assessing shape similarity. We have defined a distance function between two sets of projected feature vectors to assess the similarity between them from the cost estimation point of view. To assess similarity between the two parts, one set of projected feature vectors is transformed in space using rigid body transformations with respect to the other set such that the distance between them is minimized. The distance between the projected feature vectors is used as a measure of similarity between the two parts. The existing parts are rank ordered based on the value of the distance with respect to the new part. The cost of machining the new part can then be estimated by using the cost of previously machined parts that have a very small distance from the new part. 1. INTRODUCTION For some manufacturing domains such as rapid prototyping, reasonably accurate estimates of cost can be generated by estimating the volume or weight of the part. However, for machining, the cost estimate depends on the features of the part and automated procedures are not currently available for performing cost estimation for prismatic parts quickly. In such cases, cost estimation has to be done manually. Cost estimation can take any where from few minutes to few hours depending upon the expertise of the cost estimator and the complexity of the part. Based on our conversations with human cost estimators, it appears that many of them implicitly use estimates from previously completed tasks to generate new quotes. The cost estimators usually need to search a large database of 3D machined parts in order to find the parts that are similar to the one whose cost has to be estimated. Then the cost estimators analyze the cost of the retrieved parts in order to give an estimate of the cost of the newly designed part. Manual cost estimation is inefficient especially when the designer submits the 3D model over the Internet for getting quotes. Ideally, the designer would like to receive the cost estimate in a few seconds. One way to achieve …