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SUBJECT: Lean Production/ Lean Manufacturing
ALPHANUMERIC IDENTIFIER: Supplied by Instructor (leave space for)
BRIEF DESCRIPTION:
A concept pioneered by Toyoda Kiichiro and Taiichi Ohno at Toyota in Japan, and largely
championed by James Womack in the United States, Lean Production a philosophy that
involves empowered teams on the production floor, enhanced communication across
operations, the vigilant elimination of waste, and tireless continuous improvement. Lean
production (as opposed to mass production) is believed to require half the human effort in
the factory, half the manufacturing space, half the investment tools, half the engineering
hours, and half the product development time (Womack, 1990). Other terminology commonly
used to describe lean production include: Lean Manufacturing, Toyota Production System,
and Just In Time Manufacturing. This document will use the term "Lean" to
describe the overall concept.
KEYWORDS: LEAN PRODUCTION MANUFACTURING TOYOTA TPS JIT
OVERVIEW:
In contrast to statistical process control (SPC), which defines acceptable defect
levels, Lean sets absolute, unachievable goals so that improvement must be continual.
Edwards (1983) boils the goals down to the "seven zeros", discussed below.
Included with each goal are Lean tools which can be used in striving toward the goals. Zero
Inventories, the main driver to all the goals, is the relentless crusade to banish muda
(or waste), especially waste in the form of inventory.
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Zero Defects: zero inventories are not possible without zero quality defects, as
defects require buffer inventories to avoid disrupting production. Poka-yoke (or foolproofing)
processes to prevent human error, visual management to make quality more
readily visible, real-time root-cause problem solving (or asking the five whys)
by teams of production workers on the floor, andon cord (enabling workers to stop
the line for defects), 100 percent check (with workers correcting their own errors)
and process control run by line workers, all help approach this goal.
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Zero (excess) Lot Size (or lot size of one): larger lot sizes require excess
inventories. This goal is enabled by working toward the next goal. Since in reality lot
size of one is sometimes impossible, kanban (visual card system for managing
inventory and production) and pull scheduling set to takt time (or frequency
of orders by the customer) aid in reducing lot sizes.
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Zero Setups: the key to reducing setup times is to separate internal setup
(steps which must be done with the machine stopped) from external setup (steps
which can be done off-line while the line is still running), and to minimize the internal
setup required. Jigs, fixtures, parallel machines, and uniform product design all
contribute to reaching this goal.
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Zero Breakdowns: a zero-WIP system cannot tolerate any machine breakdowns. Preventive
maintenance is the main tool involved, along with the Five S’s: Sort
(separate out everything unneeded to reduce clutter), Stabilize (clearly identify a
place for everything and keep everything in its place), Sweep (keep the workplace
clean), Standardize (define an on-going system to institutionalize the first three
S’s), and Sustain (instill self-discipline in everyone to adhere to the
system).
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Zero Handling: if parts are made just in time, no extra moves to and from storage
can be tolerated. Cross-trained teams in flexible work cells contribute to
this goal.
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Zero Lead Time: this means both cycle times and setup times must be reduced. Kaizen,
or continuous improvement, by empowered teams aids this and all the other goals.
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Zero Surging: to achieve smooth material flow, demand surges must also be smoothed. Final
assembly scheduling, which specifies daily or even hourly production schedules
requires smoothing aggregate production requirements by working with customers and
sequencing final assembly, product by product. Capacity buffers (time between
shifts, to accommodate overtime) can help deal with inevitable surges. Mixed model
production (producing several products on the same line) also aids in preventing
surges in demand on suppliers, as does close, cooperative relationships with the
suppliers.
Lean techniques can and should be applied to all operating systems and processes,
including manufacturing, product development, and purchasing activities. Lean is not a
rigorous manufacturing process or system, but more of a philosophy, or collection of
methods and slogans. Actually implementing them requires not simply applying the tools
identified above but also making very complex tradeoffs in the overall system, paying
excruciating attention to small details that are specific to each process, and being
extremely persistent over a very long time.
For example, Toyota reduced some setups from three hours in 1945 to three minutes in
1971 (Ohno, 1988), but only through 25 years of ingenious, incremental improvements,
specific to those processes.
As such, a simple Lean implementation instruction manual is impossible to produce.
It is clear that the early pioneers guarded their developments as a competitive
advantage. Ohno admits that the Japanese used deliberately confusing terms to describe JIT
concepts (Myers, 1990). Successful implementation of Lean requires 1) a never-ending
process with deliberate cultural change from Mass to Lean thinking, 2) enduring commitment
at all levels of the organization, 3) a leader who can make tough, technical tradeoffs
while rallying people around a clear, common vision 4) countless ingenious ideas from
everyone in the organization, and 5) an empowering organizational system that maximizes
each individual’s potential contributions.
REFERENCES:
- Monden, Yasuhiro. 1998. Toyota Production System: An Integrated Approach to
Just-In-Time. Engineering & Management Press.
- Cusumano, Michael A.; Nobeoka, Kentaro. 1998. Thinking Beyond Lean : How
Multi-Project Management Is Transforming Product Development at Toyota and Other Companies.
Simon & Schuster.
- Womack, James P. 1996. Lean Thinking. Simon & Schuster.
- Toyota Motor Company. 1995. The Toyota Production System. International Public
Affairs Division & Operations Management Consulting Division, October.
- Mishina, Kazuhiro; & Takeda Kazunori. 1995. Toyota Motor Manufacturing, USA, Inc.
Harvard Business School, September.
- Womack, James P.; Jones, Daniel T.; & Roos, Daniel. 1990. The Machine That
Changed the World – The Story of Lean Production. Harper Perennial.
- Myers, F.S. 1990. "Japan’s Henry Ford." Scientific American
262(5): 98.
- Ohno, T. 1988. Toyota Production System: Beyond Large-Scale Production.
Productivity Press.
- Imai, Masaaki. 1984. Kaizen – The Key to Japan’s Competitive Success.
McGraw-Hill Publishing Company.
- Edwards, J.N. 1983. "MRP and Kanban – American Style." APICS 26th
Conference Proceedings, pp. 586-603.
ACKNOWLEDGEMENT: This is a March 29, 1999 revision by Gene Goodson of
an assignment for OM742 contributed by Charlie Choi.
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