II. OVERVIEW AND MOTIVATION

I. CHAPTER ROAD MAP

In this chapter, we first discuss why design for manufacture is important (Figure 14.1).

II. OVERVIEW AND MOTIVATION

Design for manufacture and assembly analysis and synthesis is, as with many design process methods, applicable during many phases of a product design process. It can be used in benchmarking analysis as in Chapters 6 and 7, in simplifying new concepts not yet built, and in simplifying fully embodied designs.

There are two components, design for manufacture and design for assembly. Design for manufacture CD FM) entails making piece parts easier to produce from raw stock. For example, one can make a plastic part easier to injection mold by changing its draft angle-the angle formed by the difference in wall thickness from the part at the inside of a mold compared with the wall thickness at the end of the mold. Small draft angles make for difficult part ejection. Design for manufacture involves application of part-forming models, whether they are basic rules, analytic formulas, or complex finite element process simulations.

Design for assembly entails making attachment directions and methods simpler, for example, making a part easy to attach by using snap fits instead of machine screws.

Satellites used in exploratory NASA interplanetary missions, for example, have systems that must work; saving even thousands of dollars on assembly or part cost is meaningless. What is important, however, is reliability. Any design activity that can increase reliability will be applied, and this again is a benefit of design for manufacture and assembly. For example, Motorola conducted a study showing that application of design for manufacture and assembly reduced their failure rates as shown in Figure 14.2. The reason behind this increase in reliability is basically that if the production process is simplified, then there is less opportunity for outright errors.

III. BASIC METHOD: DESIGN GUIDELINES

The most basic approach to design for manufacture and assembly is to apply design guidelines. After developing a design concept, one should examine it on each of the design guidelines and change the design to make it satisfy the guideline.

A note on design guidelines: Like all guidelines, they are heuristics that generally hold true. To every rule there are exceptions, and that holds true here as well. One should use design guidelines with an under-standing of the design goals, and ensure that application of the guideline improves the design concept on those goals.

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Date: 2016-03-03; view: 678