Institute for Systems Research

Evaluating the manufacturability of a proposed design involves determining whether or not it is manufacturable with a given set of manufacturing operations - and if so, then finding the associated manufacturing efficiency. In this research, the design is represented as a solid model. The tolerance and surface finish information is represented as attributes of various faces of the solid model. Machining features are used to model the available machining operations Since there can be several different ways to manufacture a proposed design, this requires considering alternative ways to manufacture it, in order to determine which one best meets the design and manufacturing objectives.

The approach developed in this thesis is based on the systematic exploration of various machining plans. The first step is to identify all machining features which can potentially be used to machine the given design. Using these features, different machining plans are generated. Each time a new plan generated, it is examined to find whether it can produce the desired design tolerances. If a plan is found to be capable of meeting the tolerance specifications, then its rating is computed. If no machining plan can be found that is capable of producing the design, then the design cannot be machined using the given set of machining operations; otherwise, the manufacturability rating of the design is computed. Since various alternative ways of machining the part are considered in this approach, the conclusions about the manufacturability are more realistic compared to the approach where just one alternative is considered.

It is anticipated that this research will help in speeding up the evaluation of new product designs in order to decide how or whether to manufacture them. Such a capability will be useful in responding quickly to changing demands and opportunities in the marketplace.

Even after one has decided upon al abstract set of features to use for representing manufacturing operations, the set of feature instances used to represent a complex part is by no means unique. For a complex part, many (sometimes infinitely many) different manufacturing operations can potentially be used to manufacture various portions of the part - - and thus many different feature instances can be used to represent these portions of the part. Some of these feature instances will appear in useful manufacturing plans, and others will not. If the latter feature instances can be discarded at the outset, this will reduce the number of alternative manufacturing plans to be examined in order to find a useful one. Thus, what is required is a systematic means of specifying which feature instances are of interest.

This paper addresses the issue of alternatives by introducing the notion of primary feature instances, which we contend are sufficient to generate all manufacturing plans of interest. To substantiate our argument, we describe how various instances in the primary feature set can be used to produce the desired plans. Furthermore, we discuss how this formulation overcomes computational difficulties faced by previous work, and present some complexity results for this approach in the domain of machined parts.

In this paper, we propose an architecture for integrating CAD with DFM. This involves the use of multiple critiquing systems, each one dedicated to one type of manufacturing domain. In the proposed framework, as the designer creates a design, a number of critiquing systems analyze its manufacturability with respect to different manufacturing domains (machining, fixturing, assembly, inspection, and, so forth), and offer advice about potential ways of improving the design.

We anticipate that this approach can be used to build an environment that will allow designers to create high-quality products that can be manufactured more economically. This will reduce the need for redesign, thus reducing product cost and lead time.

In particular, we present a methodology for taking a CAD model, extracting alternative interpretations of the model as collections of MRSEVs (Material Removal Shape Element Volumes, a STEP-based library of machining features), and evaluating these interpretations to determine which one is optimal. The evaluation criteria may be defined by the user, in order to select the best interpretation for the particular application at hand.

Evaluating the manufacturability of a proposed design involves determining whether or not it is manufacturable with a given set of manufacturing operations - and if so, then finding the associated manufacturing efficiency. Since there can be several different ways to manufacture a proposed design, this requires us to consider different ways to manufacture it, in order to determine which one best meets the design and manufacturing objectives.

The first step in our approach is to identify all machining operations which can potentially be used to create the given design. Using these operations, we generate different operation plans for machining the part. Each time we generate a new operation plan, we examine whether it can produce the desired shape and tolerances, and calculate its manufacturability rating. If no operation plan can be found that is capable of producing the design, then the given design is considered unmachinable; otherwise, the manufacturability rating for the design is the rating of the best operation plan.

We anticipate that by providing feedback about possible problems with the design, this work will help in speeding up the evaluation of new product designs in order to decide how or whether to manufacture them. Such a capability will be useful in responding quickly to changing demands and opportunities in the marketplace.

The information provided by these techniques will prove useful in two ways: (1) to provide information to the manufacturing engineer about alternative ways in which the part might be machined, and (2) to provide feedback to the designer identifying problems that may arise with the machining.