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The
Impact of the Toyota Production System
If
one machine stopped then shortly afterwards the whole process stopped.
Without the excess buffer stocks, the machinery and equipment became
interdependent. Hence, the availability of the process became the
product of the individual availabilities of each machine or piece of
equipment. Thus, a process involving four machines maintained at 90%
no longer had an overall process availability of 90%, but an overall
process availability of 90% X 90% X 90% X 90%, or 66%! (see Figure 2).
Furthermore,
as the quality approach changed to "Prevention at Source" by
controlling process variables, machinery and equipment performance
problems were identified much earlier resulting in conformance and
reliability becoming much more important.
As
buffer stocks reduced, process availability reduced resulting in
substantial pressure being placed on the maintenance department to
improve process performance. From a maintenance perspective, the
maintenance department's performance had not deteriorated, yet demand
for the substantial improvement in machinery and equipment
availability was overwhelming. This caused friction between the
production and maintenance departments. Production departments
demanded former levels of process availability and quicker response
times from maintenance, who were often unable to comply due to
traditional organisation structures which keep maintenance as a
separate function. After much conflict between maintenance and
production, engineering were called in to find a solution. They soon
realised that mathematically for the four machines to achieve their
original process availability goal of 90%, the machine’s individual
availability needed to increase from 90% to 97.5%.
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