The First Snap-Fit Handbook

Frontmatter

1. Introduction

Abstract

This book presents information about snap-fit technology in a logical format for learning and understanding. Once the reader understands snap-fit technology, this book will provide design guidance as a reference handbook.

Paul R. Bonenberger

2. Key Requirements

Abstract

Chapter 2 introduces the key requirements for snap-fit applications. These are common technical characteristics shared by all fundamentally sound snap-fits and satisfying them is the goal of snap-fit application development. These key requirements are the top level of the Attachment Level Construct (ALC), see Fig 2.1.

Paul R. Bonenberger

3. Introduction to the Snap-Fit Development Process

Abstract

In Chapter 2, we described the key requirements of a snap-fit application. We will skip over the elements row in Fig. 3.1, and jump to the snap-fit development process shown in the bottom row.

Paul R. Bonenberger

4. Descriptive Elements

Abstract

Chapters 2 and 3 discussed the top and bottom rows of the ALC. The center row of the ALC contains the spatial/descriptive and physical elements used to describe and construct the snap-fit interface. Those elements and some related concepts are the subjects of Chapters 4 through 9.

Paul R. Bonenberger

5. Physical Elements: Locators

Abstract

Chapter 4 introduced spatial and descriptive elements for defining a snap-fit attachment. The remaining physical elemeqents are used to build the attachment.

Paul R. Bonenberger

6. Physical Elements: Locks

Abstract

Chapter 5 introduced locators as strong and inflexible constraint features that position the mating-part to the base-part. The second constraint feature group is locks, see Fig. 6.1.

Paul R. Bonenberger

7. Lock Strength and Decoupling

Abstract

We tend to think of snap-fit lock strength as resistance to part separation. But the very first demand on a lock’s strength is surviving the strain that occurs during assembly deflection. Locks that are damaged during assembly will not be able to perform their retention function.

Paul R. Bonenberger

8. Constraint in Snap-Fit Applications

Abstract

Constraint occurs across the attachment interface where locator and lock pairs provide positioning (locating) and locking to hold the mating and base parts together, see Fig. 8.1. Forces on the application are transmitted across the interface by the constraint features.

Paul R. Bonenberger

9. Physical Elements: Enhancements

Abstract

Enhancements are the third physical element in the ALC, see Fig. 9.1. They may be distinct interface features or they can be attributes of other interface features. Most enhancements do not directly affect reliability and strength but they can have important indirect effects on strength, quality, reliability, and cost by improving the application’s robustness to manufacturing, assembly and usage variables.

Paul R. Bonenberger

10. Applying the Snap-Fit Development Process

Abstract

To provide some context for the elements and concepts discussed in Chapters 4 through 9, the Snap-Fit Development Process was introduced in Chapter 3.

Paul R. Bonenberger

11. Feature Development: Material Properties

Abstract

This chapter introduces the plastic material properties used in feature performance calculations. Actual analysis will be discussed in Chapter 13. Four material properties normally appear in these calculations: stress (σ), strain (ε), modulus of elasticity (E), and coefficient of friction (μ).

Paul R. Bonenberger

12. Lock Feature Development: Rules-of-Thumb

Abstract

Lock design is often an iterative process and rules for establishing feature dimensions can provide a reasonable starting point for lock analysis. These rules are not hard and fast, and with some experience and awareness of brittle vs. ductile behavior and material properties, the developer can bias the rules in the right direction when setting initial feature dimensions.

Paul R. Bonenberger

13. Lock Feature Development: Calculations

Abstract

Feature analysis is possible and appropriate only after a fundamentally sound attachment concept has been created and proper constraint ensures that forces in the attachment are statically determinate.

Paul R. Bonenberger

14. Diagnosing Snap-Fit Problems

Abstract

Understanding failure modes and their relationship to the most likely root causes can help with a quick and accurate diagnosis. This minimizes the cost and time impact but it also helps ensure that the proposed changes will indeed fix the problem. Nothing is worse than making changes to a product and finding that the problem still exists or has even gotten worse. (Yes, this does happen.) Accurate diagnosis is particularly valuable during product development when prototype testing may indicate the need for improvements, yet time and cost constraints limit the available options.

Paul R. Bonenberger

15. Gaining a Competitive Advantage in Snap-Fit Technology

Abstract

Engineering managers and executives should read this chapter because of the business advantages that are possible when an organization goes beyond simply teaching individuals about good snap-fit practices and becomes snap-fit capable [1].

Paul R. Bonenberger

Backmatter