Design for Reliability

Chapter 6

Process Failure Modes, Effects, and Criticality Analysis

Joseph A. Childs

Introduction

As discussed in Chapter 5, failure modes, effects, and criticality analysis (FMECA) is a tool used for addressing risk of failure. In the case of design FMECA (D-FMECA), it is extremely valuable in reviewing the design aspects of a product—from the s tandpoint of the ability to investigate possible issues for a product meeting its design requirements. Just as D-FMECA focuses on possible design failure modes at multiple levels of hardware or software structure, P-FMECA is a detailed study, focused on manufacturing and test processes and steps, required to build reliable products. The format used in this chapter is different from that discussed previously for D-FMECA, but the considerations are the same: Risks: how serious the potential event is, the chances that it will happen, and how users know about it.

Principles of P-FMECA

P-FMECA includes a review of materials, parts, manufacturing processes, tools and equipment, inspection methods, human errors, and documentation. P-FMECA reviews the build, inspection effectiveness, and test aspects of the product for possible risks of process step failures at the multiple levels of processes, including the severity of problems after the product is in the customer's hands.

The P-FMECA process is broken down into subprocesses and lower-level steps. For each step, possible problems, their likelihood of occurring, and their ability to be detected ...