Practical Reliability Engineering, 5th Edition

15

Reliability in Manufacture

15.1 Introduction

It is common knowledge that a well-designed product can be unreliable in service because of poor quality of production. Control of production quality is therefore an indispensable facet of an effective reliability effort. This involves controlling and minimizing variability and identifying and solving problems.

Human operations, particularly repetitive, boring or unpleasant tasks, are frequent sources of variability. Automation of such tasks therefore usually leads to quality improvement. Typical examples are paint spraying, welding by robots in automobile production, component placement and soldering in electronic production and CNC machining.

Variability can never be completely eliminated, since there will nearly always be some human operations, and automatic processes are not without variation. A reliable design should cater for expected production variation, so designers must be made aware of the variability inherent in the manufacturing processes to be used.

The production quality team should use the information provided by design analyses, FMECAs and reliability tests. A reliable and easily maintained design will be cheaper to produce, in terms of reduced costs of scrap and rework.

The integration of reliability and manufacturing quality programmes is covered in more detail in Chapter 17.

15.2 Control of Production Variability

The main cause of production-induced unreliability, as well as rework and scrap, is the variability ...