Total productive maintenance: six big losses and task boundaries

Why it matters

Equipment stopping is a visible loss; but not all losses that occur while equipment is running are seen as easily. Small interruptions, low speed and unacceptable products also reduce planned time. Total productive maintenance, abbreviated TPM, supports safe and stable operation of equipment while requiring these losses to be made visible. In this introductory lesson, the six big losses are used as a common classification language. Breakdown, setup, minor stoppage, speed, process defect and startup defect are examined separately. The aim is not to do the most maintenance work or to hand all work over to workers. What matters is knowing where the loss occurs and doing the suitable work with the right authority.

The six categories are linked to the OEE chain. In this lesson's recording rule, breakdown and setup are availability loss. Minor stoppage and low speed kept within run time fall into performance loss. Process defects and startup defects form the quality loss. The recording threshold of a minor stoppage can be different in another application; if the threshold changes, the view across categories can change. What matters is that the same event is not counted again as a full loss in two places and that the period total closes. The classification is explained together with the conditions in which the record arose. A startup defect is also not added again to setup downtime merely because it occurred in the first part of production; the ideal-time equivalent of the defect stays in its own category.

Not all numbers carrying a minutes heading may have the same meaning. For a breakdown there is a real stoppage duration. The quality loss, on the other hand, can be converted to equivalent minutes by multiplying the number of unacceptable products by the ideal cycle time. This value is not a claim that the defective parts were produced for exactly that long on the wall clock. The common ideal-time base allows losses to be compared in the same time chain. Adding rework labor to this equivalent time without explanation would be summing the same product loss with different scopes. Cost, per-person workload and equipment ideal time are separate measures. When it is not clear which one is reported, the total of the six categories gains a misleading certainty.

A worker knowing the equipment and reporting an abnormality early is valuable. However, a defined cleaning or visual inspection task does not give authority to remove a guard or carry out specialist repair. In the task boundary, safe access, energy state, competence and permit conditions must be stated. Finding an abnormality and correcting it can be different responsibilities. When a worker notices a hazard, they follow the safe stop and reporting route; they do not make an unauthorized intervention to reduce production loss. In this lesson, no decision that deepens maintenance priority by equipment criticality is built; that assessment is in M18. Here, the right loss class, the right time base and the safe task boundary are learned together. Data notice for this lesson's figures, examples, counterexamples and three short quiz questions: This dataset was generated synthetically for training; it does not represent a real business, employee or customer study.

Formula