Management Techniques for Quality and Process Improvement (TQC, TQM, Six Sigma, TOC)

TQC (Total Quality Control) is an activity in which every department and every employee, not just manufacturing, takes part in improving quality.

Rather than weeding out defective products at inspection after the fact, it reworks how design, purchasing, sales and other work is done so that defects are not produced in the first place. In Japan it spread widely together with improvement activities run by small workplace groups. Policy management (方針管理), which breaks top management's policy down into departmental goals and action plans to drive improvement, is a representative TQC technique.

AnalogyThink of a restaurant where, instead of one inspector opening the boxes at the very end, everyone from kitchen prep to the front of house nips mistakes in the bud at their own station.

How to rememberThe T stands for Total: quality is not the business of one corner of the factory, and the whole company owns it.

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TQM (Total Quality Management) extends the ideas of TQC and puts quality at the core of management, continuously raising customer satisfaction and the quality of work across the organization.

Its scope goes beyond how well products turn out to cover the quality of services, business processes and management decisions. Goals are set from the customer's point of view, and the PDCA cycle keeps running company-wide so that improvement takes root.

AnalogyIt is like taking the hygiene and taste-control habits built up in the kitchen and turning them into a management policy for the whole restaurant, down to how suppliers are chosen and where new branches open.

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Six Sigma (シックスシグマ) is a quality improvement method that captures the results of products or work as measurements and reduces defects by statistically shrinking their variation.

Variation is how far results drift each time even when the same work is repeated, and statistics expresses it with the Greek letter σ (sigma, the standard deviation). The 6σ in the name comes from the goal of holding variation down so far that defects stay at a few per million opportunities. Improvement can proceed, for example, through the sequence called DMAIC: define, measure, analyze, improve and control.

AnalogyIf the bread you bake each morning swings widely in weight from day to day, you log the flour and the oven temperature, track down the cause and get every batch to come out the same weight.

How to rememberThe σ in the name is the statistical symbol for standard deviation, so the name itself tells you this method speaks about quality in data.

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TOC (Theory of Constraints) is the idea of concentrating improvement on the bottleneck (constraint) that caps the output of a chain of steps, so as to achieve overall optimization.

A bottleneck is the point in a chain of steps with the lowest capacity, which sets how much can flow downstream. Total output cannot exceed that point's capacity, so speeding up only the other steps just piles up work in process in front of it or leaves later steps waiting, without raising results. Maximizing the result of the connected whole, rather than the efficiency of each part, is called overall optimization.

AnalogyWhen four people pass parcels down a line, the parcels stall at the slowest person, so the other three hurrying does not increase how much gets moved.

How to rememberThe idea was spread by Goldratt, a former physicist, in The Goal, a novel about turning a factory around.

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