Total Quality Management or TQM is a management strategy to embed awareness of quality in all organizational processes. Quality assurance through statistical methods is a key component. TQM aims to do things right the first time, rather than need to fix problems after they emerge or fester.
In a manufacturing organization, TQM generally starts by sampling a random selection of the product. The sample is then tested for things that matter to the real customers. The causes of any failures are isolated, secondary measures of the production process are designed, and then the causes of the failure are corrected. The statistical distributions of important measurements are tracked. When parts' measures drift out of the error band, the process is fixed. The error band is usually tighter than the failure band. The production process is thereby fixed before failing parts can be produced.
It's important to record not just the measurement ranges, but what failures caused them to be chosen. In that way, cheaper fixes can be substituted later, (say, when the produce is redesigned), with no loss of quality. After TQM has been in use, it's very common for parts to be redesigned so that critical measurements either cease to exist, or become much wider.
It took people a while to develop tests to find emergent problems. One popular test is a "life test" in which the sample product is operated until a part fails. Another popular test is called "shake and bake." The product is mounted on a vibrator in an environmental oven, and operated at progressively more extreme vibration and temperatures until something fails. The failure is then isolated and engineers design an improvement.
A commonly-discovered failure is for the product to come apart. If fasteners fail, the improvements might be to use measured-tension nutdrivers to assure that screws don't come off, or improved adhesives to assure that parts remain glued.
If a gearbox wears out first, a typical engineering design improvement might be to substitute a brushless stepper motor for a DC motor with a gearbox. The improvement is that a stepper motor has no brushes to wear out, and no gears to wear out, so it lasts ten times or more longer. The stepper motor is more expensive than a DC motor, but cheaper than a DC motor combined with a gearbox. The electronics is radically different, but equally expensive. One disadvantage might be that a stepper motor can hum or whine, and usually needs noise-isolating mounts.
Often a TQMed product is cheaper to produce (because there's no need to repair dead-on-arrival products), and can yield an immensely more desirable product.
TQM can be applied to services (such as mortgage issue or insurance underwriting), or even normal business paperwork.
TQM is not a focused improvement approach. The customer desires and product tests select what to fix. Theoretical constraints are not considered at all.
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