Bhargava Robust Plastic Product Design: A Holistic Approach

1. Auflage 2017
ISBN: 978-1-56990-581-4
Verlag: Hanser Publications
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 344 Seiten

Tooling, molding, secondary operations, material selection, evaluation and testing, design, project management, costing, value engineering, international supplier management and enhancement, and more: this book provides a broad insight from the author’s over 40 years of experience in the plastics industry.
Aimed at both technical and non-technical personnel involved with plastic product design and manufacturing, this book shows how having the big picture leads to effective solutions and high-quality products. Numerous case studies of product failures exemplify the key concepts.
The reader will benefit from the author’s unique depth and breadth of knowledge and experience as a team manager and hands-on contributor in all aspects of plastics, involving extremely robust, mission-critical products. Judicious attention to fundamental engineering principles is always at the foundation but “people issues” are also brought into focus from the author’s background as a long-time international trainer and Six Sigma expert.
The book is therefore an essence of all the experience gained along the way: the good, the bad, and the ugly.
This book is unique among the many other fine books available in this subject area in that it is the perspective of one who has been in the trenches—as opposed to an academician, scientist, or other professional from a field with narrower scope, such as material science, tooling, or manufacturing. Hence, the HOLISTIC APPROACH.
Contents:
• Causes of Plastics Failure
• The Holistic Approach
• Plastic Materials
• Design
• Tooling Considerations
• Processing
• Secondary Operations
• Part and Tool Costs
• Six Sigma Techniques in Plastics
• Further Reading and Reference Material
With forewords by Glenn Beall, Louis Maresca, and Joe McFadden.

Autoren/Hrsg.

Bhargava, Vikram

Leseproben

1.	Introduction

1.1	Causes of Plastics Failure

In his book Failure of Plastics and Rubber [1], David Wright conducted an analysis on 5,000 failed parts and came up with the causes for the failures shown in Figure 1.1.

Figure 1.1 Causes of plastics failure [1]

Therefore, a designer may conclude that he or she is responsible for only twenty percent of the failures. As will be shown in the following chapters, what appears as materials, processing, tooling, or misuse issues may be traced back to fundamental design issues that may manifest themselves as the former.

Let us assume for the moment that design issues do cause only twenty percent of the failures, and the designer proactively makes sure that this 20% has been reduced to zero. Even then, in order to be certain that the product meets all the functional and cost requirements, someone needs to take responsibility for ensuring that the other three areas are optimized. The presence of designated materials, tooling, and processing specialists in the organization notwithstanding, that someone is still the designer!

1.2	The Holistic Approach

Let us look at the classical definition of the word "holistic" [2]:

holistic

adjective ho·lis·tic \ho-'lis-tik\

1: of or relating to holism

2: relating to or concerned with wholes or with complete systems rather than with the analysis of, treatment of, or dissection into parts; holistic medicine attempts to treat both the mind and the body; holistic ecology views humans and the environment as a single system

In the case of a well-designed plastic part or assembly, the parts are:

• Material

• Design

• Tooling

• Processing

• Secondary operations

The analogy I have used over my years of conducting training on this subject is that material, design, tooling, and processing are like the four wheels of a high performance car.

One bad wheel and...

On the other hand, if all of the four wheels are taken care of, one can have a product that can last for years and withstand a lot of so-called "abuse." During my training sessions I often show the video 1 of a handheld terminal 2 with proper consideration to the four "wheels." In the video this terminal is tossed to the high ceiling of a warehouse multiple times, dropping back each time on a hard concrete floor. It is also kicked around and used as a hammer on the concrete floor. At the end of the video, there is no crack or break and the terminal functions normally.

Figure 1.2 Symbol/Motorola/Zebra terminal MC9200

1.2.1

The Four Wheels

The following list contains most, but not all, of the considerations a designer needs to take into account in order to create a robust product.

1.2.1.1

Material

• Basic physical properties

  • Static: mechanical—tensile strength, toughness, elongation, etc.

  • Dynamic: wear, modulus at high impact rate, fatigue

  • Electrical: dielectric strength, resistance, etc.

  • Long term: color retention, embrittlement

• Environmental properties

  • Chemical resistance

  • Color and appearance

• Thermal properties

  • High and low temperatures

  • Temperature cycling

• Agency requirements

  • UL

  • FDA

  • RoHS

  • REACH

  • Country specific requirements

• Molding properties

  • Flow: MFI, flow length vs. thickness

  • Bonding between materials (overmolding)

  • Directional shrinkage

1.2.1.2

Design

• Purely physical requirements

  • Mechanical—tensile strength, toughness, elongation, thermal properties, etc.

  • Electrical—dielectric strength, resistance, etc.

  • ESD (electrostatic discharge)

• Molding and tooling dependent requirements

  • Gate size, appearance, and location

  • ...