The Elements of Part Design

Introduction

Plastic part development considers not only the design, but the material, tooling, and manufacturing process. These four key elements of design success need to be held in balance to achieve success and lowest total cost.

This article was originally part of Profile’s Design Guide. Plastics industry legend Glenn Beall wrote our first edition in 1985. Hidden away in the company archives for years, the concepts presented here can offer valuable insight for creating successful parts today.

What are the four key elements of design success?

Designing a part for pressure forming is like designing something for any other plastic process. It starts with creating a shape or structure that satisfies the functional needs of the product in its final end-use environment. 

Once the functional requirements are understood and a basic shape has been evolved, the designer turns his attention to the materials and fabrication techniques to produce the part. Many materials and process options are available. 

All successful plastic products have four basic elements in common. Each must be handled correctly to produce an optimum plastic part. 

1. the design of the part
2. the selection of the ideal plastic material
3. the design and construction of the tooling
4. the processing or forming and finishing of the part

A successful product starts with a high quality part drawing. Design and development of plastic products is never as easy as the designer is led to believe it will be. A good drawing results from meticulous attention to detail, coupled with a designer’s knowledge of the capabilities and limitations of the material, tooling and process.

How to keep the elements in balance?

The designer needs to first acquire at least a basic understanding of these three additional elements. In other words, a plastic part must be proportioned according to the requirements of the specific material, the unique tooling and the best process.

To ignore or mishandle any of these elements will result in a less-than-best product. It creates a break in the inherently strong circle that surrounds and protects a successful plastic part. If the circle is broken, the product will suffer unnecessary high tooling or piece part cost, poor quality, inadequate strength, appearance problems, a lack of customer satisfaction … or all the above.

While satisfying these requirements, the designer must not lose sight of the functional requirements of the part in its end-use environment. Product development often necessitates painful compromises. For example, you may choose injection molding; however, marketing will not wait for the long tool delivery schedule. Or the product would be stronger in polycarbonate, but the market won’t accept the increased material cost.

Conclusion: Lean on the Design Guide

Profile’s Design Guide and technical articles answer the designer’s questions. They provide a quick way to discover what you need to know to take advantage of pressure forming for your new plastic product.