Designing Plastics Parts for Assembly

Foreword to 2nd Edition

Henri (Ari) Sayag,

Research Manager,


February 1995 Monte Carlo, Monaco

Plastic parts and plastic materials have had a bad image over the decades. This was due to inadequate design, poor knowledge of both materials and manufacturing. Many products were rejected after disastrous first trials, and this situation lead managers to turn back to traditional solutions excluding plastic materials.

Paul A. Tres is a part of the generation which made the pioneering times of plastic technology turn toward the modern era. Those, nostalgic of the trial and errors method, of heroic adjustments with an after taste of weariness, may not appreciate this book. Those who have never lived these days and nights of anguish, trying and trying, increasing a radius here, adding draft angle there, adding thickness and so on, cannot understand how important it is to get ready–to–bake solutions. That's the task of this book and it is well done. It will enable all those searching for effectiveness and the best time-to-market, to find a method, I would even say a recipe. You can find here, in terms of assembly, the right solution, including the right material, to meet the requirements of your product. This book is one of those which shows that the plastic material technology has reached the age of reason. The frontiers of voodoo will be set back and as each time limits are pushed back, new solutions, and innovative applications appear on the market. The professionals then know how to do things better, inspiring confidence in their clients, and others who are often far away from the world of plastics. This restored confidence allows people to consider daring solutions, since we are surrounded by a deep knowledge of the materials, and their behavior in all the situations they will come across during their lifetime. As in any good Hollywood movie, the happy end is then assured. However it is still not easy, the bad experiences of the near past and certain adventurers who ignore or disdain these tools make it difficult to restore full confidence to the users.

One must admit that before the advent of analytical methods the anxiety of the customer was absolutely legitimate. Paul's book contributes to the establishment of fruitful dialog between the client and his supplier. The client can begin his concept on a solid, communal basis, thus allowing a notable more savings, fewer second thoughts because of the recognized scientific basis on one hand and the fine tuning added by Paul's substantial experience on the other hand.

Compared to metals, plastic materials present many advantages but have one major defect: they have characteristics which vary significantly according to temperature and time. This makes plastic design not as easy to deal with as metal design. Plastic expertise is needed, as well as specific knowledge about operating conditions. Mostly, the failure in plastic design takes place when the designer is not aware of two topics:

- Safety factors

- Behavior of plastic materials

The advice I can provide you, is to begin your reading with chapter 2. You will find an exhaustive panorama of the safety factors you will need to deal with while designing in plastic. Afterwards, in chapter 1, spend the time you need to understand why plastic materials may have such a surprising behavior compared to metal. Then, you are free to choose the assembly technique that fits your product.

Nevertheless, I have one regret. Paul and I often discussed the opportunity to write a book summing up our experience. Paul did it. I did not. I hope one day, I can forgive him!

©1995 Carl Hanser Verlag. All rights reserved.

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