METHODS ENGINEERING:Within-Operation Analysis

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3.5. Within-Operation Analysis

This section will discuss fish diagrams, decision structure tables, and checklists.

3.5.1. Fish Diagrams

Fish diagrams graphically depict a multidimensional list. See Figures 20 and 21. Professor Ishikawa developed them while on a quality control project for Kawasaki Steel; they are the ‘‘cause’’ side of cause-and-effect diagrams. The diagram gives an easily understood overview of a problem.

Start with the ‘‘effect’’ (a fishhead), a specific problem. Then add the ‘‘cause’’ (the fish body), composed of the backbone and other bones. A good diagram will have three or more levels of bones (backboneA, major bones, minor bones on the major bones). There are various strategies for defining the major bones. Consider the 4 M’s: manpower, machines, methods, materials. Or use the 4 P’s: policies, procedures, people, plant. Or be creative.

Figures 20 and 21 were used at Bridgestone to reduce the variability of the viscosity of the splicing cement used in radial tires. Figure 21 shows the variability of the four operators before and after the quality circle studied the problem.

A very effective technique is to post the fish diagram on a wall near the problem operation. Then invite everyone to comment on possible problems and solutions; many quality problems can be reduced with better communication.

3.5.2. Decision Structure Tables

Decision structure tables are a print version of ‘‘if, then’’ statements (the ‘‘what if’’ scenario) in computer programs. They also are known as protocols or contingency tables; see Table 21 for an example. They unambiguously describe complex, multivariable, multirule decision systems. A spread- sheet is a computerized decision structure table.

Decision structure tables give better quality decisions due to (1) better decision analysis (higher- quality personnel make the decision, using complex analysis techniques if necessary) and (2) less time pressure at the time the decision is made. They are a game plan worked out in advance, not in the heat of battle. However, in addition, decision structure tables force a good methods analysis because all possibilities are considered systematically. The tables also are good training aids.

3.5.3. Checklists

Checklists allow a novice to use the distilled expertise of others. Table 6 is a checklist to prioritize potential ergonomic problems; it focuses on force, duration, and repetition for various body parts.

SNAG-0039

SNAG-0040
clip_image005Checklists can also focus more precisely. Table 7 is a checklist for just the upper extremity. Table 8 is a checklist to prioritize potential ergonomic problems due to posture; it focuses on force and duration for neck, trunk, and general body.

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