6. Quality in Automotive Engineering

Introduction
One of the vital changes that has occurred in the past 100 years of car manufacture is the improvement in the quality of the product. Where manufacturers have gone out of business, in many cases a key reason was the poor quality of the vehicles they produced. The Japanese companies have demonstrated that in a mass market a technically superior product with indifferent quality will ultimately be unsuccessful against a technically mundane product which is built to a high level of quality.
A vital difference in the 1950s 60s and 70s was that many UK manufacturers operated on 'development led' philosophy, they did some design, made prototypes tested and developed these, improved them and then started selling to the public. There were a number of disadvantages in this approach:

  • development testing did not reveal all the faults
  • it is much more expensive to make changes to fix problems once prototypes are built
  • paying customers often received cars with faults
  • faults in customers cars were often not properly fixed

The Japanese manufacturers understood these pitfalls and avoided them by putting in a lot of thought and effort at the design and planning stages. Changes are much less costly to make at this early stage in the design / manufacturing cycle. The other key feature of Japanese operations was that they understood that quality was fundamental and they adopted methods and practices whereby everyone in an organisation took responsibility for quality and played a part. Quality improvement has to come about via 'prevention of' rather than 'inspection of' to eliminate defective components.

The result of this was that although Japanese cars of the 60s and 70s were technically mundane, they were generally far more reliable than most UK manufactured vehicle, even though some of these were more innovative (the Mini). This then led to Japanese manufacturers capturing an increasing proportion of the UK car market.
The activities, tools and 'philosophies' used and developed, many of them by the Japanese companies, include: Taguchi, Statistical Process Control (SPC), Quality Circles, Commitment to Teamwork, Robust Design.

Taguchi considers quality loss - deviation from the target value - as a 'cost to society', which is all embracing. The fundamental idea of 'robust design' is to improve the quality of a product by minimising the effects of the causes of variation without eliminating the causes. This is achieved by optimising the product design and process specification to minimise the sensitivity of the product performance to the variations that occur in the manufacturing process (both specifiable process parameters and random or non controlled effects). This procedure is called parameter design, ref. Q1.

References
Q1: Quality Engineering Using Robust Design, by M S Phadke, Prentice Hall, 1989.

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David J Grieve, 30th July 2001.