Handbook of Molded Part Shrinkage and Warpage

2nd Edition

Print ISBN: 9781455725977
eBook ISBN: 9781455730575
Imprint: William Andrew
Published Date: 26th December 2012
Page Count: 292
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How easy life would be if only moldings were the same size and shape as the mold. But they never are, as molders, toolmakers, designers and end users know only too well. Shrinkage means that the size is always different; warpage often changes the shape too. The effects are worse for some plastics than others. Why is that? What can you do about it? The Handbook of Molded Part Shrinkage and Warpage is the first and only book to deal specifically with this fundamental problem. Jerry Fischer’s Handbook explains in plain terms why moldings shrink and warp, shows how additives and reinforcements change the picture, sets out the effect of molding process conditions, and explains why you never can have a single ‘correct’ shrinkage value. It goes on to demonstrate how to alleviate the problem through careful design of the molded part and the mold, and by proper material selection. It also examines computer-aided methods of forecasting shrinkage and warpage. And most important of all, the Handbook gives you the data you need to work with.


Key Features

  • Authoritative and rooted in extensive industrial experience, the expert guidance contained in this handbook offers practical understanding to novices, and new insights to readers already skilled in the art of injection molding and mold making.
  • Contains the answers to common problems and detailed advice on how to control mold and post-mold shrinkage and warpage.
  • Case Studies illustrate and enrich the text; Data tables provide the empirical data that is essential for success, but hard to come by.


Engineers, scientists and technicians specializing in injection molding of plastic components. Designers of plastic components. Process and product manufacturing control engineers. Product development engineers.

Table of Contents

PDL Handbook Series



1. Introduction to Injection Molding

1.1 Introduction to Plastics

1.2 Interactivity Basics

1.3 Thermal Principles Governing Injection Molding


2. Shrinkage and Warpage

2.1 In-Mold Shrinkage

2.2 Warpage

2.3 Postmold Shrinkage


3. Causes of Molded-Part Variation: Part Design

3.1 Wall Thickness

3.2 Ribs

3.3 Bosses

3.4 Example of Proper Part Design

3.5 Other Design Considerations


4. Causes of Molded-Part Variation: Material

4.1 Amorphous and Semicrystalline Resins

4.2 Effects of Fillers, Reinforcements, Pigments, Time, and Stress

4.3 Shrinkage Predictions: Using PVT Relationships


5. Causes of Molded-Part Variation: Mold Design

5.1 Cavity Dimensions and Design Factors

5.2 Gate Types

5.3 Gate Location

5.4 Gate Size

5.5 Gate Design Systems

5.6 Runner Design

5.7 Mold Cooling Design

5.8 Mold Construction Materials

5.9 Prototype Molding with Stereolithography or Similar Type Molds

5.10 Pitfalls to Avoid


6. Causes of Molded Part Variation: Processing

6.1 Molding Conditions

6.2 Injection Melt Temperature

6.3 Injection Rate and Pressure

6.4 Holding Pressure and Time

6.5 Mold Temperature

6.6 Demolding Temperature

6.7 Molded-In Stresses

6.8 Other Molding Processes


7. Factors Affecting Postmold Shrinkage and Warpage

7.1 Effects of Temperature on Dimensions

7.2 Effects of Moisture on Dimensions

7.3 Creep


8. Controlling Mold and Postmold Shrinkage and Warpage

8.1 Finding the Cause

8.2 Processing Considerations

8.3 Material Considera


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© William Andrew 2013
William Andrew
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"This is a great book."--INJECTION MOLDING