PRODUCTION SYSTEMS AND OPERATIONS MANAGEMENT
- ©1998 Joseph Martinich. All rights reserved.
None of these materials can be stored,
transmitted or reproduced by any means
(electronic, mechanical, photocopying or
otherwise) without the written permission of Joseph
Martinich. These materials may be used by
students in classes taught by Professor
Martinich at University of Missouri - St. Louis.
Quick Set-ups (Single-Minute-Exchange-of-Dies - SMED)
- If a production process or work station is supposed to produce several
different products there will typically be time and cost required to make the
- Setting up a machine or process is not a value-adding activity.
- Definition of Set-up Time for a machine, work-station or process: The time
between production/processing of the last unit of one product/lot and when
the first good unit of the next product/lot is produced.
- Other definitions
- Machine: A piece of equipment that is fundamental to the
operation. It is typically the focus of the set-up. Set-up involves
doing something to the machine so it can produce different
- Fixture: A device attached to a machine to adapt it for a
particular use. This includes dies, nozzles, blades, drill bits,
cutting heads, extensions, and guide bars.
- Tool: A device for installing fixtures and adjusting fixtures and
machines, such as screw drivers, wrenches, and pliers.
- Typically we have addressed the large cost/time of set-ups by:
- Having specially trained set-up workers who are especially skilled at
setting up equipment
- Problem: Other workers have to wait around until the set-up
workers can set up for the next run
- Producing in large batches to minimize the number of set-ups
- Example: If set-up time is 8 hours and running time per unit is
1 minute then for a batch of 100 units the average time/cost is
[8(60 min.) + 100(1 min.)]/100 units = 5.80 min/unit
If we increase lot size to 10,000, the average time/cost is
[8(60 min) + 10000(1 min)]/10000 = 1.048 min/unit
This is an 82% reduction in per unit cost.
- BUT - the average cycling inventory is 100 times
larger, and the cycle time between product runs is
20 times larger
- Combine or sequence products/jobs that are similar so the change-over between runs is simpler.
- This can be beneficial, but the risk is that it will cause late
deliveries of other products. The sequencing of work is set by
what product is currently running, rather than what is needed
now. Similar to large lot size approach.
- We have generally treated setup time and cost as inherent to a process and
not changeable. But:
- Small-Lot, Kanban scheduling requires that set-ups be performed
quickly, because the number of set-ups is much larger than with large
- To move closer to the ideal production system, we need to reduce set-up time. So Lean Production treats set-up time as changeable and
- If set-up time/cost can be reduced, the effect on optimal lot-size
can be substantial. For example, if the set-up time in the earlier
example is reduced from 8 hours to 10 minutes:
Then for a batch of 100 units the average time/cost is
[10 min. + 100(1 min.)]/100 units = 1.10 min/unit
If we increase lot size to 10,000, the average time/cost is
[10 min + 10000(1 min)]/10000 = 1.001 min/unit
Thus, the benefits from increasing lot sizes are small.
- Shigeo Shingo has developed some structured methods for reducing set-up
In 1950, while working for Toyo Kogyo's Mazda plant, Shigeo
Shingo began his systematic study of production set-ups.
Worker looking for a bolt to make die change; while looking
for correct bolt, the entire stamping operation is idle
His "solution" of modifying a bolt from another machine was
time-consuming, and created another set-up problem for the
- Internal Versus External Set-up Activities
- Observations lead to the recognition that set-up activities can
be classified as either "Internal" or "External"
- Internal set-up activities, such as mounting a die or
changing the ink cartridge on a photocopier, are
activities that can be performed only while the
equipment or process is stopped.
- External setup activities, such as collecting all bolts
needed to mount a die or unpackaging an ink cartridge
from its carton, are those that can be done while the
equipment is operating.
- By making sure external set-up activities were done
while the process was operating Shingo cut set-up time
more than in half.
- Changing Internal Set-up to External Set-up
- Shingo was observing a large side-planer used to machine diesel
engine beds: much time was spent,"... centering and dimensioning the
engine bed ... on the planar table itself."
- The planar had to be shut down while this was done, so it was
treated as an internal set-up activity.
- By adding second table, this could be done as external set-up
- Procedure for Reducing Set-up Times (SMED)
- Reported cases: Toyota Motor Company bolt-making machine set-up
reduced from 8 hours to 1 minute. Set-up for a boring machine at
Mitsubishi Heavy Industries reduced from 24 hours to under 3
- SMED follows a simple five step procedure:
1. Observe and analyze in detail how the set-up is currently
2. Eliminate any unnecessary tasks.
3. Of the activities currently performed, separate internal set-up
activities from external set-up activities, and perform external
activities while the process is operating.
4. Wherever possible convert internal set-up activities to external.
5. Simplify and streamline all activities.
1. Observe and Analyze the Existing Process
- An essential feature of set-up time reduction is understanding
how the set-up is currently being performed.
- Create activity charts, worker-machine charts, and set-up work-sheets
- Worker-machine chart tracks what worker(s) and
machine/process are doing simultaneously. Can
see whether machine idleness is being created by
poor sequencing of worker's activities
- Videotape set-ups
- Invaluable in showing workers what they are
currently doing and how the set-up can be
2. Evaluate Each Task and Try to Eliminate as Many as Possible
- Using the activity charts and worker-machine charts and
set-up worksheet, analyze each task that is performed.
Try to eliminate as many tasks as possible using a five
why's or value/process analysis approach (e.g., why is
this task being done? What does it contribute to the set-up? Could it be done as part of another task?).
- This evaluation/elimination is repeated during each of
the following steps
3. Separate Internal Set-up Activities from External Activities and
Perform External Activities while the Process/Machine is
- Many set-up tasks that are performed while production is
stopped are really external activities that could easily be
performed while the machine/process is operating.
- Make sure all external set-up activities are performed while the
process is operating, either perform external activities for a set-up while production on the previous job/batch is occurring or
after production of the new product/batch has begun (e.g.,
replacing materials in storage).
- Make a written set-up plan that sequences when each
of the activities are to be performed. Clearly highlight
the external activities.
- The plan should list any parts, tools, and fixtures
needed, and any numerical values of any settings
or dimensions for the machines or fixtures.
- Make a checklist of all the items (parts, fixtures, tools)
needed for each set-up/changeover. Then create a
"part-holder" box (or set-up kit) that will hold the parts
and tools needed, with the list attached, so the worker
can check off parts as she gathers them before the set-up.
- Prepare and test parts and tools, transport parts and tools
to the machine, bring necessary materials to the machine
and transport materials removed from the machine as
- Test parts before stopping the process: One of the
biggest wastes of set-up time results from not
discovering a part needed for the set-up is defective until
the internal set-up is being performed; by checking and
testing parts during the external phase, these delays are
- Store parts, fixtures, and tool so they are easy to find and
easy to remove and replace. Store materials needed for a
set-up as close together and near the machine as
- Improve the coordination of material transport so
materials are moved while machines are running. Let
machine operators transport their own materials.
- Moving and pre-positioning materials as an external
activity may involve more total work than transporting
materials as part of the internal set-up activities, but if it
converts internal to external work then there may still be
a net improvement in productivity.
4. Redesign Internal Set-up Activities to Convert Them to External
- Activities that appear to be internal activities can sometimes be
converted to external activities by changing work methods,
adding work aids, adding extra tables, vats, or containers,
preheating or precooling, materials, or using container liners.
- Heating/Cooling of molds or heating/cooling/mixing of
- Rather than doing all of the heating/cooling or
mixing of materials as part of the internal set-up,
which is common, preheating or precooling of
materials can often be done external to the set-up
so that final heating/cooling during the internal
set-up phase requires less time. Frequently waste
heat from other operations can be used to do this
which results in an energy saving as well.
- Cleaning activities
- Have two or more sets of tools or processing
vessels; the dirty or contaminated ones can be
replaced with clean ones quickly during internal
set-up, and then the dirty ones can be cleaned after
production has restarted. For fluid vessel cleaning,
rather than having two separate vessels, a lower
cost solution is often to use plastic vessel liners
which can quickly be exchanged.
5. Simplify and Streamline Activities
- The primary focus should be on reducing the time to perform
internal set-up activities because this will reduce production
- The best way to reduce set-up activity times is by task
simplification and task elimination.
1. External set-ups time can be reduced through better tool
and material storage and transport.
- Have tools stored neatly in racks
- Each worker/work-station could have its own tools
- Each worker/work-station could have its own
2. Dies and other parts that must be changed during set-ups
should be standardized in size and shape.
- Dies or tools can be inserted and removed like
"cassettes" in a cassette player without having the
calibrate and align the die or tool.
3. Use the same standard components and fasteners for each set-up
- This way the fasteners stay with the machine, and they
simply have to be loosened and re-tightened for each
set-up, rather than removed, replaced, transported and
- Ideally use only one type of fastener (e.g. bolts) so only
one tool is needed and fasteners cannot be mixed up.
4. Use fasteners that can be loosened and tightened with a single
turn, rather than those that require turning the fastener several
revolutions. Use fasteners and attachments that can be installed
with a single tool.
5. Reduce or eliminate adjustments by using fixed settings and
markings on dies, tables, and guide bars. Every set-up can be
pre-marked so that tools and dies do not have to be measured
each time; the "mark-points" on the dies and tools simply have
to be matched with those on a table or guide bar.
6. Have two or more workers doing the internal set-up in parallel.
For example, if adjustments have to be made by going back and
forth between the front and back of a machine, the walking can
be eliminated by having two workers do this.
- Generalization of SMED Techniques
- Can be used for any changeover, including changing a printer
cartridge in a printer or a worn blade or drill bit in a machine), for
performing many maintenance and repair jobs, or for changing from
serving one customer to another customer in a service system.
- Benefits of Quick Set-ups
- Quick set-up methods result in simpler, more structured set-up
procedures. This produces many benefits other than the obvious cost
- Can make products in smaller batches, which reduces WIP and
finished product inventories.
- Simpler set-ups require less skilled workers (operators can do
set-ups instead of set-up specialists). Production workers are
not left idle while set-up specialists do the set-up. Set-up
specialists can focus on the more difficult set-ups.
- Simpler, structured set-ups usually produce less start-up scrap
- Simpler, structured set-ups result in fewer mistakes that can
cause defects. Trial-and-error adjustments are eliminated.
- Production Flexibility
- Can switch among products more quicker to adjust to changes
in demand mix
- Quicker set-ups effectively create additional capacity at no
cost; eliminates need for more equipment, workers, and
- Shorter set-up times and smaller lot sizes reduces the
throughput time. Can compete on speed more effectively.
- Process Variability
- Structured, simpler set-ups have less variability in set-up time,
as well as less average time. We have seen how variability
wastes capacity and creates inventories.
Page Owner: Joseph Martinich (Joseph.Martinich@umsl.edu)
Last Modified: February 5, 1999