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SMED - Single Minute Exchange
of Dies
SMED is a
powerful technique, used to reduce the amount of
time required for equipment / machine setup or
line changeover. The technique was first
developed by Shigeo Shingo of Toyota in the
1950's, with the aim of reducing downtime from
more than 24 hours to less than 10 minutes for
the changing of dies on press tools. The
phrase "single minute" does not mean
that all changeovers should take only one
minute, but that they should take less than 10
minutes ie single (digit) minute. When
applying SMED techniques for the first time it
is often possible to halve the time taken.
50% savings can be achieved,
but I think it's important to say that this is
only likely to apply if you haven't previously
done any SMED activities.
In order to
complete a SMED exercise you must first step
back and observe a process changeover, and the
best way to observe and record a changeover is
to video it. Once you have finished
recording the changeover the entire team,
including the operatives, should watch the
video, and create a SMED timesheet, by listing
all of the tasks required for the changeover,
and how long each task took to complete.
The next
step is to separate the internal tasks
(activities) from the external tasks
(activities). Internal activities are
those that can only be performed when the
process is stopped, while external activities
can be done while the process is ongoing, for
example getting the required tools for the job
before the process stops. Mark on your
SMED Timesheet those tasks which are
internal and those which are external.
You
need to ensure that all external activities are
actually done before the changeover. In
practice, many external tasks are actually
performed during set-up / changeover, (eg people
fetching tools, looking for instructions etc)
resulting in unnecessary downtime.
Typically this will account for around half of
the total time taken.
Once
you have identified the internal tasks, the next
step is to brainstorm ideas for converting
internal activities into external activities,
for example pre-heating tools. In other
words, change the activities so that they can be
done while the machine or process is
on-going. Any internal activities that
cannot be converted need to be
streamlined. For example try to get rid of
nuts and bolts and use clamps, use intermediate
jigs, and eliminate adjustments. Consider
manning levels, eg could two people do it in
less than half the time that one person would
take? Think about training / practising or
even having a dedicated changeover team.
Finally,
remember to document the new procedure (think
about creating checklists and written
procedures) and training any relevant personnel.
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