What it means
Traditional factories group machines by function, so all the drills sit in one area and all the presses in another. Each job travels long distances, waits in queues and builds up piles of unfinished goods.
A manufacturing cell, by contrast, places the machines needed for a product family side by side in process order. Cellular manufacturing is closely tied to lean production, a method that aims to remove waste.
In a cell, workers are cross-trained, parts move in small batches or one at a time, and problems show up immediately because the next station is only a step away. This reduces work in progress (WIP), which is the value of partly finished goods sitting on the factory floor.
The financial benefits show up in several places. Lower WIP releases cash that was tied up in inventory, shorter lead times allow faster delivery and reduce stock holding costs, and fewer defects reduce scrap and rework.
Floor space is also freed because there is less queuing material. Cells work best where products are similar enough to share the same sequence of operations, and where volumes are high enough to justify dedicated machines.
They are less suitable for very varied or low-volume work. A cell is only as fast as its slowest step, called the bottleneck, so balancing the work between stations is essential.
Setting up a cell has costs, including moving equipment, retraining staff and sometimes buying duplicate machines. A business case should compare those costs with the savings in inventory, labour and space.
The best cells keep improving after launch, using regular reviews to shorten the slowest step. People are central to success.
Cross-trained operators who can run several machines, and who are encouraged to stop and fix problems, are what turn a good layout into a better business.
In practice
Real-world examples.
Example
A furniture maker arranges saws, sanders and assembly benches into a cell for table legs. A leg now moves from raw timber to finished part in two hours instead of three days. The workshop no longer needs a large area for stacks of half-finished parts.
Example
An electronics assembler creates a cell for one family of circuit boards. Workers are cross-trained, so when one station slows down, a colleague helps and the flow continues. Output per worker rises because less time is lost waiting for material.
Example
A medical device manufacturer sets up a cell for a high-volume product line. Quality checks are built into each step, and defects are caught immediately rather than at the end of the line. Scrap costs fall because faulty parts are not passed along.
Formula
Calculation
Cell output per shift = Available minutes per shift / Bottleneck cycle time
Inventory carrying saving = Reduction in WIP units x Unit cost x Carrying cost rate
A cell has three stations with cycle times of 4, 6 and 5 minutes. The slowest is 6 minutes, so with 480 available minutes per shift the output is 480 / 6 = 80 units. Before the cell, the process held 600 units of WIP, and afterwards it holds 120, a reduction of 480 units. At a unit cost of $50 and a carrying cost rate of 20% a year, the saving is 480 x $50 x 0.20 = $4,800 a year.Case study
Seen in the real world.
Ashford Metalworks is an illustrative, fictional manufacturer of brackets and fittings. Its old layout sent each batch through five separate departments, and the average order took nine days to complete.
The operations manager grouped the cutting, bending, drilling and finishing machines for its three best-selling brackets into a cell. After the change, lead time fell from nine days to two, and work in progress fell by about 70%.
In this illustrative story, the finance director valued the released inventory and the freed floor space, and found that the cost of moving the machines was recovered in under a year. The business case succeeded because it measured cash tied up in stock as well as labour hours.
Watch out
Common mistakes.
- Treating a cell as a cosmetic change in layout, when it also needs cross-trained staff and a pull system for work.
- Ignoring the bottleneck, which sets the pace of the whole cell no matter how fast the other stations are.
- Counting only labour savings in the business case and overlooking inventory, space and quality benefits.
Questions
People also ask.
What products suit manufacturing cells?
Families of similar products with the same sequence of operations and enough volume to keep the cell busy.
How do cells help cash flow?
They reduce work in progress and shorten production time, which frees cash that would otherwise be tied up in inventory.
Do cells need new machines?
Not always, but sometimes duplicate machines are needed so that each cell is self-contained.
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