The diagram systematically represents and analyses the real causes behind a problem or effect. It organises the major and minor contributing causes leading to one effect (or problem), defines the problem, identifies possible and probable causes by narrowing down the possible ones. It also helps groups to be systematic in the generation of ideas and to check that it has stated the direction of causation correctly. The diagrammatic format helps when presenting results to others.

2.2. Dr Genichi Taguchi (1924)believed it is preferable to design product that is robust or insensitive to variation in the manufacturing process, rather than attempt to control all the many variations during actual manufacture. To put this idea into practice, he took the already established knowledge on experimental design and made it more usable and practical for quality professionals. His message was concerned with the routine optimisation of product and process prior to manufacture rather than quality through inspection.

Quality and reliability are pushed back to the design stage where they really belong, and he broke down off-line quality into three stages:

• System design

• Parameter design

• Tolerance design

“Taguchi methodology” is fundamentally a prototyping method that enables the designer to identify the optimal settings to produce a robust product that can survive manufacturing time after time, piece after piece, and provide what the customer wants.

Fig. 2.5. Quality control procedure and stages of evolution

2.3. Shigeo Shingo (1909-1990)is strongly associated with Just-in-Time manufacturing, and was the inventor of the Single Minute Exchange of Die (SMED) system, in which setup times are reduced from hours to minutes, and the Poka Yoke (mistake proofing) system. In Poka Yoke, defects are examined, the production system stopped and immediate feedback given so that the root causes of the problem may be identified and prevented from occurring again. The addition of a checklist recognises that humans can forget or make mistakes.

He distinguished between “errors”, which are inevitable, and “defects”, which result when an error reaches a customer, and the aim of Poka Yoke is to stop errors becoming defects. Defects arise because errors are made and there is a cause and effect relationship between the two. Zero quality control is the ideal production system and this requires both Poka Yoke and source inspections. In the latter, errors are looked at before they become defects, and the system is either stopped for correction or the error condition automatically adjusted to prevent it from becoming a defect.

VOCABULARY PRACTICE

Refer back to the text and find English equivalents of the following Russian word combinations.