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TOTAL PRODUCTIVE MAINTENANCE:
Total productive maintenance (TPM) is the systematic execution of maintenance
by all employees through small group activities.
The dual goals of TPM are zero breakdowns and zero defects; this obviously
improves equipment efficiency rates and reduces costs. It also minimises inventory
costs associated with spare parts.
It is claimed that most companies can realise a 15-25 percent increase in equipment
operation rates within three years of adopting TPM. Labour productivity also
generally increases by a significant margin, sometimes as high as 40-50 percent.
The Japanese imported preventive maintenance (PM) from the United States in
the 1950s and it remained well established until the 1970s. This consisted mainly
of time-based maintenance featuring periodic servicing and overhaul. During
the 1980s PM was steadily replaced by predictive maintenance, or condition-based
maintenance (see RELIABILITY-CENTRED MAINTENANCE). TPM is often defined as productive
maintenance involving total participation - a kind of marriage between PM and
TQM. Many organisations misconstrue this to imply that only shop floor staff
need be involved. However, TPM should be implemented on a company-wide basis.
TPM aims to establish good maintenance practice through the pursuit of "the
five goals of TPM" :
(1) Improve equipment effectiveness: examine the effectiveness of facilities
by identifying and examining all losses which occur - downtime losses, speed
losses and defect losses.
(2) Achieve autonomous maintenance: allow the people who operate equipment
to take responsibility for, at least some, of the maintenance tasks. This can
be at :
the repair level (where staff carry out instructions as a response to a problem);
the prevention level (where staff take pro-active action to prevent foreseen
problems); and the
improvement level (where staff not only take corrective action but also propose
improvements to prevent recurrence).
(3) Plan maintenance: have a systematic approach to all maintenance activities.
This involves the identification of the nature and level of preventive maintenance
required for each piece of equipment, the creation of standards for condition-based
maintenance, and the setting of respective responsibilities for operating and
maintenance staff. The respective roles of "operating" and "maintenance"
staff are seen as being distinct. Maintenance staff are seen as developing preventive
actions and general breakdown services, whereas operating staff take on the
"ownership" of the facilities and their general care. Maintenance
staff typically move to a more facilitating and supporting role where they are
responsible for the training of operators, problem diagnosis, and devising and
assessing maintenance practice.
(4) Train all staff in relevant maintenance skills: the defined responsibilities
of operating and maintenance staff require that each has all the necessary skills
to carry out these roles. TPM places a heavy emphasis on appropriate and continuous
training.
(5) Achieve early equipment management: the aim is to move towards zero maintenance
through "maintenance prevention" (MP). MP involves considering failure
causes and the maintainability of equipment during its design stage, its manufacture,
its installation, and its commissioning. As part of the overall process, TPM
attempts to track all potential maintenance problems back to their root cause
so that they can be eliminated at the earliest point in the overall design,
manufacture and deployment process.
TPM works to eliminate losses :
- Downtime from breakdown and changeover times
- Speed losses (when equipment fails to operate at its optimum speed)
- Idling and minor stoppages due to the abnormal operation of sensors, blockage
of work on chutes, etc.
- Process defects due to scrap and quality defects to be repaired
- Reduced yield in the period from machine start-up to stable production.
See Nakajima, S. (1988). Introduction to Total Productive Maintenance. Cambridge,
MA: Productivity Press
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