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TPM and OEE

Total productive maintenance (TPM) includes a series of improved methods based on team work concept in accordance with common targets by incorporating the other parts except maintenance to works about equipment.

In TPM process, we can subsume the wastes which decrease equipment activity under three titles and six groups.

1- Availability wastes (Failure wastes/Set-up and setting wastes)

2-Performance wastes (Speed wastes/Small waiting wastes)

3-Quality wastes (Error, reprocessing wastes/Start-up wastes)

 

TPM and losses

1- Availability wastes

We define the wastes which prevent machine’s producing and decrease the planned producing time as waiting wastes. In TPM concept, these kinds of wastes are called as wastes which step down availability percent. Failure and set-up, setting wastes constitute the basis for these kinds of wastes.

a- Failure wastes: These are waiting wastes which are caused by equipment failures needing repair. Generally using equipment under suboptimal conditions, using operator-based wrong equipment, missing and insufficient maintenance activities, using unstable part may cause this sort of wastes.

b- Set-up and setting wastes: These are wastes which are caused by changes in stream of producing. The time to catch the real machine performance during production return, producing starting in the morning, preparing and tests like machine’s starting to produce again after shift starting or break coming back may cause these wastes.

2- Performance wastes

These are wastes which are decreasing performance and take part of the net operation time which remain after waiting wastes are removed from planned producing time.

a- Speed wastes: The reason of these wastes is that equipment is not being worked under the ideal speed. Especially in some processes, running the machine with maximum speed may cause degradation in the quality. In these kinds of cases, machine’s performance is brought down running more slowly and tries to come over with the quality problem.

b- Small stoppage wastes are generally caused by small waiting which is under 5 minutes and can be solved by operators without maintenance department response.

3- Quality wastes

These wastes decrease quality percent and are caused by defective products which are produced in exact operation time.

a- Error and reprocessing wastes: They are caused by defective products in producing process. Defective products become either waste or a new product by being processed again. In either case, wastes like labor, energy and raw material occur.

b- Start-up wastes: They are producing mistakes which occur during process before serial production (first setting tests to start the series). Especially we can put the wastes which we have in production returns and at first step of new production until the first indefectible product is produced into this group of wastes.

The following statement shows the effect of these wastes to the time. As it is seen, factory operation time (t0) fell down productive operation time (t4) by effects of wastes which we mentioned above. The target of TPM is to minimize the difference between these two times.

 

Overall Equipment Effectiveness (OEE)

We analyzed the effects of wastes which occur in management equipment above. Effects of these three wastes must be analyzed together to measure effectiveness of equipment. So we call results which are given by showing the effects of availability, performance and quality indicators at the same time as overall equipment effectiveness.

OEE= Availability x Performance x Quality

Availability= Time of operation which is carried out/ Exact available operation time

Performance= Ideal cycle time x Production / Time of operation which is carried out

Quality= The number of indefectible products / The number of total products

 

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