INTRODUCTION TO DESIGN FOR MANUFACTURING

By -

1. INTRODUCTION

The objective of design for manufacturability is to incorporate producibility issues early on in the product design stage so that the customers can be attracted and the needs of the customers can be satisfied in a short lead time and at a competitive cost. The customers’ needs include satisfaction in the product with respect to its performance capabilities, quality, reliability, serviceability, aesthetics, and time of delivery.

SNAG-0002

Conventional engineering practice in the past has resulted in separate, and sometimes isolated, activities between design and manufacturing that have proven to be time consuming and costly. A study compared the cost of any change in design in three different stages, namely, in production, manufacturing engineering, and design. The cost of a change in the production stage may be ap-

SNAG-0003

SNAG-0004

proximately an order of magnitude more than the cost of the change made early in the manufacturing engineering stage. Figure 1 shows comparative cost of an engineering change in different stages in the product cycle. To avoid the costly changes due to manufacturability problems, factors related to manufacturing must be considered in all phases of the design process, starting with the design- conception phase. Another study (Nevins and Whitney 1989) further confirmed the importance of making the right decision early. This study indicated that in the concept formulation stage 60% of the life-cycle cost of a product has already been determined. Before full-scale development 75% of the life-cycle cost has been determined. This is illustrated in Figure 2. It is clear from the figure that the DFM needs to be considered in the early conceptual design stage to yield the maximized benefits.

The major issues in competitiveness have moved from cost to productivity to quality. The current and future major issue is time. The other issue are not less important, but the new frontier is speed: studies have shown that over 80% of market share in a new product category goes to the first two companies that get their products to market. Further studies have shown that a 20% cost overrun in the design stage of the product cycle will result in about 8% reduced profits over the lifetime of the product. A six-month overrun in time during the design stage today will result in about 34% loss over the life of the product (Brazier and Leonard 1990).

Figure 3 compares Japanese and U.S. auto design and product cycles. The competitive advantage of the Japanese auto industry results from concurrent engineering and design for manufacture (Shina 1991).

Comments

Post a Comment

Popular posts from this blog

DUALITY THEORY:THE ESSENCE OF DUALITY THEORY

By -
Image
THE ESSENCE OF DUALITY THEORY Given our standard form for the primal problem at the left (perhaps after conversion from another form), its dual problem has the form shown to the right. Thus, with the primal problem in maximizatio n form, the dual problem is in minimization form instead. Furthermore, the dual problem uses exactly the same pa r amete r s as the primal problem, but in different locations, as summarized below. 1. The coefficients in the objective function of the primal problem are the right-hand sides of the functional constraints in the dual problem. 2. The right-hand sides of the functional constraints in the primal problem are the coef- ficients in the objective function of the dual problem. 3. The coefficients of a variable in the functional constraints of the primal problem are the coefficients in a functional constraint of the dual problem. To highlight the comparison, now look at these same two problems in matrix notation (as introduced at the beginn
Read more

NETWORK OPTIMIZATION MODELS:THE MINIMUM SPANNING TREE PROBLEM

By -
Image
THE MINIMUM SPANNING TREE PROBLEM The minimum spanning tree problem bears some similarities to the main version of the shortest-path problem presented in the preceding section. In both cases, an undi r ecte d and connected network is being considered, where the given information includes some mea- sure of the positive length (distance, cost, time, etc.) associated with each link. Both problems also involve choosing a set of links that have the shortest total length among all sets of links that satisfy a certain property. For the shortest-path problem, this property is that the chosen links must provide a path between the origin and the destination. For the minimum spanning tree problem, the required property is that the chosen links must provide a path between ea c h pair of nodes. The minimum spanning tree problem can be summarized as follows: 1. You are given the nodes of a network but not the links. Instead, you are given the po- tential links and the positive length for each
Read more

NETWORK OPTIMIZATION MODELS:THE SHORTEST-PATH PROBLEM

By -
Image
THE SHORTEST-PATH PROBLEM Although several other versions of the shortest-path problem (including some for directed networks) are mentioned at the end of the section, we shall focus on the following simple version. Consider an undi r ecte d and connected network with two special nodes called the origin and the destination. Associated with each of the links (undirected arcs) is a non- negative distance. The objective is to find the shortest path (the path with the minimum total distance) from the origin to the destination. A relatively straightforward algorithm is available for this problem. The essence of this procedure is that it fans out from the origin, successively identifying the shortest path to each of the nodes of the network in the ascending order of their (shortest) distances from the origin, thereby solving the problem when the destination node is reached. We shall first outline the method and then illustrate it by solving the shortest-path problem encountered by the See
Read more