Chapter 8
Part Design
In this chapter:
Purpose
Introduction
Part Requirements
Performance Requirements
Production Process
Part Specifications
Part Design
Design Basics
Shrinkage
Sinks Marks
Surface Blemishes
Weight Reduction
Insulation
Transparency
Corrosion and Chemical Resistance
Color and Texture
Molded-In Hinges
Assembly
Fabrication and Fastening
Post Molding Operations
Material Selection
Prototype Mold
Thermoformed Prototypes
Cast Prototypes
Machined Prototypes
Molded Prototypes - Die-Try
Computer Aided Design and Manufacturing
Computer Aided Design
Computer Generated Prototypes
This chapter introduces key concepts which underscore the creation of any plastic piece: a material's properties, part design, developing a prototype; and the object's environmental needs. The chapter also introduces the use of computers for the simultaneous design, analysis, and simulated manufacture of plastic parts and prototypes.
Introduction
Designing a plastic part necessitates the simultaneous consideration of part requirements, a material's properties, the manufacturing process, and mold design. Traditionally, the procedure to produce parts treated each of these factors as separate processes. However, today's accelerated pace requires the simultaneous integration of all four factors into one process. These four factors are interdependent; a change in one aspect will affect the suitability of a decision made later in the design process. This new integrated design process is called "design for manufacture ability". Four factors underscore this design process. Figure 8-1 illustrates how this process works in practice.
Design for manufacture ability and dissassembly dictates that the four factors must be compatible and able to tolerate one another. The designer focuses on the total process of design and manufacturing at the beginning of the design process. The simultaneous consideration of part requirements, material properties, manufacturing process and mold design contribute to the complex nature of plastic part design. Once the designer understands all these factors and includes their unique restriction as part of the design process, then a successful plastic part can be manufactured.
The complexity of design for manufacture ability requires the designer to be both technically sound and creatively active in all aspects of the design process. The creative process of the part designer must be rigorously disciplined and constantly mindful of these four factors. The use of computers has accelerated the seamless fusion of design concepts and technical requirements. Figure 8-2 illustrates this computer-integrated design approach.
