Manufacturing Process Selection Handbook

K. G. Swift, J. D. Booker

• Publisher: Butterworth-Heinemann
• Year: 2013
• Print ISBN: 9780080993607
• eBook ISBN: 9780080993577
• Topic: Technology & Engineering
• Subtopic: Industrial Engineering
• Index: Technology & Engineering

Manufacturing Process Selection Handbook provides engineers and designers with process knowledge and the essential technological and cost data to guide the selection of manufacturing processes early in the product development cycle. Building on content from the authors' earlier introductory Process Selection guide, this expanded handbook begins with the challenges and benefits of identifying manufacturing processes in the design phase and appropriate strategies for process selection. The bulk of the book is then dedicated to concise coverage of different manufacturing processes, providing a quick reference guide for easy comparison and informed decision making. For each process examined, the book considers key factors driving selection decisions, including: - Basic process descriptions with simple diagrams to illustrate - Notes on material suitability - Notes on available process variations - Economic considerations such as costs and production rates - Typical applications and product examples - Notes on design aspects and quality issues Providing a quick and effective reference for the informed selection of manufacturing processes with suitable characteristics and capabilities, Manufacturing Process Selection Handbook is intended to quickly develop or refresh your experience of selecting optimal processes and costing design alternatives in the context of concurrent engineering. It is an ideal reference for those working in mechanical design across a variety of industries and a valuable learning resource for advanced students undertaking design modules and projects as part of broader engineering programs. - Provides manufacturing process information maps (PRIMAs) provide detailed information on the characteristics and capabilities of 65 processes in a standard format - Includes process capability charts detailing the processing tolerance ranges for key material types - Offers detailed methods for estimating costs, both at the component and assembly level

Chapter 1

Introduction to the Handbook

1.1 The Economic Case for Manufacturing Process Selection

A productive manufacturing engineering sector comes from making the best use of our manufacturing processes – understanding and utilising their technological capabilities and the economic opportunities they can offer. If we can get the quality and cost of our products right for our customers, then our businesses will reap the financial rewards. It is often thought that selecting manufacturing processes for making our products is the responsibility of the production people. In reality, this can be highly influenced by design – the processes used can be largely predetermined by the design alternative selected: choice of materials, sizes, shapes, finishes and tolerances, etc. Therefore, process options should feature at the concept selection stage. There are always design alternatives, with some being more economic and robust than others. All other things being equal, the design professional should select the most competitive design in terms of quality and cost while ensuring that the functional requirements of the design are met.

So the designer has the huge responsibility of guaranteeing that the product will conform to customer requirements, comply with specification and ensure quality in every aspect of the product, including its manufacture and assembly, all within compressed timescales. Cost and quality are essentially designed into products (or not!) in the early stages of the product introduction process and thus consideration of manufacturing problems at the design stage is the major means available for reducing manufacturing costs, improving quality and increasing productivity. Such considerations are particularly important in the current economic climate, where the vast majority of (if not all) manufacturing businesses are facing pressure on their margins. Therefore, this Handbook has been designed to make process selection easy, efficient and effective, providing a ready opportunity to engineer a product that gives customers the functional performance they want at a competitive price and with a minimum of design risk.

Regarding design risk, the company that waits until the product is at the end of the line to measure its conformity and cost will not be competitive. The need to understand and quantify the consequences of design decisions on product manufacture and quality of conformance has never been greater. It has been found that more than 30% of product development effort can be wasted on rework [1] and it is not uncommon for manufacturing operations to have a ‘cost of quality’ equal to 25% of total sales revenues [2].

Why do we continually face these difficulties? The costs ‘fixed’ at the planning and design stages in product development are between 60% and 85%, while the costs actually incurred at that stage range from only 5% to 7% [3]. Therefore, the more problems prevented early on, through careful engineering of a design for manufacture, the fewer problems that have to be corrected later when they are difficult and expensive to change.

Increasing manufacturing efficiency, improving quality and reducing costs does not only accrue from investment in automation and advanced machine tools. The benefits of picking the right process can be enormous. This point is illustrated in Figure 1.1, which shows the relative costs and technical merits for a number of components, and resulting from alternative processing routes.

Figure 1.1 Contrast in Component Cost for Different Processing Routes.

We know from Design for Manufacture (DFM) and Design for Assembly (DFA) research that huge savings can also be made at the product level. The results of numerous applications of these approaches, carried out across a wide variety of industries, show average part-count reductions of almost 50% and average assembly cost savings of 45%. Associated savings in product cost of the order of 30% are not uncommon [4–7].

Where do these product savings come from? DFA is particularly interesting in the context of this Handbook, since its main benefits result from systematically reviewing functional requirements and replacing component clusters by single integrated pieces and by selecting alternative joining processes [4]. Therefore, invariably the proposed design solutions rely heavily on adopting different manufacturing processes – material combinations as shown in the part-count reduction examples in Figure 1.2. (A number of guidelines for manufacturing and assembly-oriented design are provided for the reader in Appendices A and B.)

Figure 1.2 Sample DFA Case Studies to Illustrate the Power of Process Selection (Example 1 after Ref. [4], Example 2 after Ref. [7]).

So what’s the underlying problem? While some designers have practical experience of production processes and understand the limitations and capabilities they must work within, there are many more that do not [4]. The designer needs to be aware of the importance of manufacturing and assembly, and understand the processes and capabilities they are designing for in order to mitigate problems and potentially save money. Furthermore, the effects of assigning tolerances and specifying geometry and materials in design have far-reaching implications on manufacturing operations and service life, and the associated risks are rarely (if ever) properly understood. Understanding the effects of variability and the severity/cost of failure is key to risk assessment and its management.

The use of design techniques such as DFM and DFA early in the product development process has emerged as an effective way of reducing costs and improving competitiveness as they help measure the performance of designs and support the experience of the designer. In order to achieve the required quality and cost objectives for the manufacture of a design, it is necessary to carry out the interrelated activities of selecting candidate processes and tuning a design to get the most out of a chosen manufacturing route. This is not always so easy, particularly in the situation of new product development. In most cases there are several processes that can be used and selection depends on a large number of factors.

Different manufacturing technologies such as primary shape-generating processes, joining techniques and assembly systems require that selection takes place based on the factors relevant to that particular technology. Although there may be many important selection drivers with respect to each process technology, a simple and effective strategy for selection must be sought for the general situation and for usability.

Selection strategies based on key economic and technical factors interpreted from the Product Design Specification (PDS), or other requirements, are necessary. The selection strategies, together with the information provided by design guidelines, in-house data and handbooks, must complement business strategy and the costing of designs in order to provide a procedure that fully justifies final selection.

1.2 Manufacturing Process Information for Designers

The need to provide the design activity with information regarding manufacturing process capabilities and costs has been recognised for many years and some of the work that has been done to address this problem will be touched up on. However, there is relatively little published work in this area. The texts on design rarely include relevant data and while a few of the volumes on manufacturing processes do provide some aid in terms of process selection and costing [8–13], the information is seldom sufficiently detailed and systematically presented to do more than indicate the apparent enormity of the problem. Typically, the facts tend to be process specific and described in different formats in each case, making the engineer’s task more difficult. There is a considerable amount of data available but precious little knowledge of how it can be applied to the problem of manufacturing process selection. The available information tends to be inconsistent: some processes are described in great detail, whilst others are perhaps neglected. This may give a disproportionate impression of the processes and their availability.

Information in manufacturing texts can also be found displayed in a tabulated and comparative form on the basis of specific process criteria. While useful, the design-related data tends to be somewhat limited in scope and detail. Such forms may be adequate if the designer has expertise in the respective processes, but otherwise, gaps in the detail leave room for misconceptions and may be a poor foundation for decision-making. Manufacturing catalogues and information on the Internet can be helpful; however, they tend to be sales orientated and, again, data is prese...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Preface
• Acknowledgements
• Notation
• Chapter 1. Introduction to the Handbook
• Chapter 2. Process Selection Strategies and Case Studies
• Chapter 3. Casting Processes
• Chapter 4. Forming Processes
• Chapter 5. Plastics and Composites Processing
• Chapter 6. Machining Processes
• Chapter 7. Non-traditional Machining Processes
• Chapter 8. Rapid Prototyping Processes
• Chapter 9. Surface Engineering Processes
• Chapter 10. Assembly Systems
• Chapter 11. Joining Processes
• Chapter 12. Component Costing
• Chapter 13. Assembly Costing
• Appendices
• Bibliography
• Index