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Introduction to cellular manufacturing
Original text on www.freequality.org
In today’s
business world, competitiveness defines an industry leader. The drive toward maximum efficiency is
constantly at the forefront of such companies’ objectives. Managers across the country are striving to
adopt lean manufacturing practices to help address worries about their bottom
line. Cellular Manufacturing is one
staple of lean manufacturing.
Cellular
Manufacturing is an approach that helps build a variety of products with as
little waste as possible. A cell is a
group of workstations, machine tools, or equipment arranged to create a smooth
flow so families of parts can be processed progressively from one workstation
to another without waiting for a batch to be completed or requiring additional
handling between operations. Put
simply, cellular manufacturing groups together machinery and a small team of
staff, directed by a team leader, so all the work on a product or part can be
accomplished in the same cell eliminating resources that do not add value to
the product.
How
to incorporate cellular manufacturing
The
implementation process of shedding the traditional manufacturing processes and
embracing the drastically different cellular manufacturing techniques can be a
daunting task. Management must deal
with many issues including: cell design
and set up, team design and placement, employee training, teamwork training, as
well as other company functional issues.
A project team should be put together that consists of management and
production employees to handle these changes.
Cell Design
and Setup should be
executed to facilitate the movement of the product through its production cycle
and should also be able to produce other similar products as well. The cells are arranged in a manner that
minimizes material movement and are generally set up in a “U” shaped
configuration.
Team Design
and Placement is a
crucial part of the process. Employees
must work together in cell teams and are led by a team leader. This team leader becomes a source of support
for the cell and is oftentimes responsible for the overall quality of the
product that leaves his/her cell.
Employee
Training must also
accompany the change to cellular manufacturing. In cellular manufacturing workers generally operate more that
one machine within a cell which requires additional training for each employee
creating a more highly skilled workforce. This cross-training allows one
employee to become proficient with his/her machines and while also creating the
ability to operating other machines within the cell when such needs arise.
Teamwork
Training should generate
camaraderie within each cell and stimulate group related troubleshooting. Employees within each team are empowered to
employ ideas or processes that would allow continuous improvement within the
cell, thus reducing lead times, removing waste and improving the overall
quality of the product.
Other issues that must be addressed include changes in
purchasing, production planning and control, and cost accounting
practices. Arranging people and
equipment into cells help companies meet two goals of lean manufacturing: one-piece flow and high variety
production. These concepts dramatically
change the amount of inventories needed over a certain period of time.
·
One-piece
flow is driven by the needs of the customer and exists when products move
through a process one unit at a time thus eliminating batch processing. The goals of once-piece flow are to produce
one unit at a time continuously without unplanned interruptions and without lengthy
queue times.
·
High-variety
production is also driven by the needs of the customer who expect customization
as well as specific quantities delivered at specific times. Cellular manufacturing provides companies
the flexibility to give customers the variety they demand by grouping similar
products into families that can be processed within the same cell and in the
same sequence. This eliminates the need
to produce products in large lots by significantly shortening the time required
for changeover between products.
Benefits
of cellular manufacturing
Cellular
manufacturing creates the ability to incorporate one-piece flow production
which produces multiple time and monetary benefits. First, it reduces material handling and transit times. By having the machinery to complete a
certain process grouped together in a cell, the product spends more time on the
machinery and less time in transit between machines. Unlike batch processing, materials do not accumulate at a certain
location to be worked or moved. This
allows the operator the ability (in most cases) to move the unfinished product
to the next station without the need of specialized equipment to move what
would be, in a batch process, a larger load, farther distances.
With decreased
material handling and transit time, accompanied by virtually eliminating queue
times associated with batch processing, comes shortened part-cycle times. In other words, the time it to produce one
unit of a particular product resulting in shorter delivery dates for the
customer.
Also associated
with one-piece flow are reduced work-in process inventories. With a continuous and balanced flow of
product through the cell, no major buildup of material occurs between
workstations eliminating the need of excess space to store in-process
goods. This also allows workstations
and/or machinery to be moved closer together.
Less WIP is easier to manage and allows the manufacture to operate with
shorter lead times.
Another benefit
of cellular manufacturing is based on the capability to produce families of
similar products within each cell.
Adjustments required to setup machinery should not be significant for
each family product. Reduced change
over times will enable more frequent product line changes and items can be
produced and delivered in smaller lots sizes without significant cost
implications.
In addition to
the aforementioned production benefits, there are also numerous benefits that
are associated with the employees and their involvement in each cell. First, a cell on average employs a small
number of workers that produce the complete part or product. Workers become multifunctional and are
responsible for operating and maintaining numerous pieces of equipment and or
workstations. They are also able to
cover other workstations within the cell when required to do so.
In terms of
worker productivity, the ability to deal with a product from start to finish
creates a sense of responsibility and an increased feeling of teamwork. A common purpose is created and gives ”ownership”
to the production teams. Feedback on
quality and efficiency is also generated from the teams building continuous
improvement within the cells and adjusting quality issues right away and not
after an entire batch has been produced.
An
example of cellular manufacturing in use
Tribon Bearin
Company, a manufacture of discrete carbon composite parts and shapes, had been
plagued by such problems as erratic product flow, high work in process
inventories, poor quality and accountability.
To make matters worse, their key customer, General Electric Aircraft
Engines, was due to audit the Tribon’s inventory turns and scrap rates for its
supplier rating system. Tribon was a
traditional manufacturing facility and its operations were highly
compartmentalized which created transfer waste and also distrust and bad
feelings distrust and bad feelings between front-line management and production
floor workforce.
After being
acquired by DuPont, DuPont Tribon Composites or DTC, decided to implement
cellular manufacturing in its production process. Two years later, the plant had installed and implemented six
workcells. Within three years, the
plant’s fixed cost productivity improved by 100 percent and on-time delivery
increased by more than 75 percent.
Constrained by
the layout of the building, DTC, built a new plant designed with specifications
to implement manufacturing cells and allow room for expansion. Within a week of the move, DTC was able to
accept a 50 percent growth in orders due to the current cellular manufacturing
setup.
Efforts were made
to provide cross training whenever possible.
The plant has instituted a skill rating system to guarantee that
employees become sufficiently skilled.
Ninety percent of the plant floor personnel are now able to perform any
job on the production floor adding flexibility.
Product quality
has been the biggest benefit from the switch to cellular manufacturing. Quality planning, team members inspecting
their own work, and a sense of ownership for the items they produce has
decreased the scrap rate of the Tribraid product, which accounts for one-third
of DTC’s sales, from 20 percent to approximately five percent. Inspection is completed after every stage in
the production process, eliminating the need for end-of-line inspections.
Before the switch
to cellular manufacturing, the Tribon plant had total annual revenue of $10.6
million and employed 106 individuals.
DTC installed its last cell in 1998 and in the year 2001, it had
revenues of $31 million generated from its 11 workcells and 140 employees. It is also a winner of the GE Supplier
Excellence award from GE Aircraft Engines.
Where
to get more information on Cellular Manufacturing
The Handbook
of Cellular Manufacturing Systems, Shahrukh A. Irani (Editor), published by John Wiley & Sons, Inc.
Reorganizing
the Factory: Competing through Cellular
Manufacturing, Nancy Hyer
and Urban Wemmerlov, published by Productivity Press, Inc.