Preface to 3rd Edition
Glenn L. Beall
Glenn Beall Plastics, Ltd.
January 1998 Libertyville, Illinois
I am delighted with the opportunity to endorse this "Third Edition" of Paul Tres' Designing Plastic Parts for Assembly.
For the past forty years, the use of plastic materials has increased at an average annual rate of 8.5%, which is more than double the growth in the GNP (Gross National Product). The plastics industry now employs 1.2 million people in over 20,000 facilities, producing over $225 billion worth of products.
In spite of plastic's impressive past and present growth, and its future prospects, teaching institutions have not responded in a responsible manner. There are not enough universities offering plastics technology curriculums. An unacceptable number of engineers receive their degrees without learning basic plastics technology. On the job, these new plastics industry professionals are, all too often, left on their own to master the technology by the laborious trial and error method of sink or swim. The old design adage that form should follow function is all too often replaced by form following failure. These inexperienced engineers can shorten the learning process with plastic technology seminars, conferences and texts such as Designing Plastic Parts for Assembly.
The manufacturers of durable products are desperately trying to improve their efficiency in order to compete and survive in a global economy. Many new management procedures are being tried. One system that has proven to be effective is DFMA or Design for Manufacturability and Assembly.
DFMA is all encompassing, but there are two important aspects that are addressed by Paul's book. Design for Manufacturability translates into keeping the design simple so that the product will be easy to manufacture. All manufacturers have to endorse this philosophy.
The assembly part of DFMA encourages the designer to also consider ease of assembly while designing the part for its intended function. All manufacturers can also endorse this philosophy.
The surest way to simplify assembly is to eliminate it. Assembly can be eliminated by combining the function of two parts into a single component. Designers pursuing this approach have seized upon plastic's ability to produce complex parts. Replacing two or more pieces with one always produces a more complex part. These complex parts are more difficult to produce, and that is in conflict with keeping it simple so it will be easy to manufacture.
Eliminating assembly is desirable, but financial management's fixation on downsizing by eliminating assembly workers has pushed this approach to, and sometimes beyond, the limit. This problem is intensified by inexperienced design engineers who, due to no fault of their own, do not know when assembly is better than parts consolidation.
All assembly cannot be eliminated. Designing Plastic Parts for Assembly explains how to optimize assembly in those situations where assembly is the best approach. This is not just a book on assembly. This is an engineer's handbook on both part design and assembly. In fact, the first four chapters do not address assembly, but dwell on the basic plastic materials technology that allows a designer to understand the whys and the hows of designing for each of the assembly procedures that are detailed in the rest of the book.
It is important to note that this book is an excellent blend of the always important basics and the latest in plastic design technology. Paul goes beyond the standard rule of thumb examples and introduces the reader to the newer, high–tech methods of designing via stress analysis. This allows the reader to go into as much depth as is required for a given project. This updated and expanded Third Edition provides design engineers with the knowledge necessary to optimize assembly procedures, while designing plastic parts that are properly proportioned for efficient manufacturing.
I have no reservations in recommending this book to the plastic product design community.
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