Monday, February 17, 2014

Positive and Negative of Lean Production

Lean production is aimed at the elimination of waste in every area of production including customer relations, product design, supplier networks and factory management. Its goal is to incorporate less human effort, less inventory, less time to develop products, and less space to become highly responsive to customer demand while producing top quality products in the most efficient and economical manner possible.
Lean manufacturing has been adoptted in more and more manufactures since its success of Toyota's TPS system. the shift from traditional manufacturing to a more systematic and integrated lean production is not a easy move for many companies to change in both way of "flow" and the culture of the organization. The slow process for companies to adopt lean manufacturing has proved there are still chanllenges and difficulties to be overcome in order to transform into a successful lean production approach.
The article of Edward J. Phillips disscussed the prons and cons of a company when adopting the lean production especially during the transform of cellular production.
1. Shorter lead time (for low to medium lot quantities) from order taking to shipping.
2. Much reduced (and preferably eliminated) work-in-process (WIP) inventories outside the cell.
3. Potential large space savings as a result of reduced WIP.
4. Tendency to have higher quality output (out-of-spec problems are discovered much sooner, before the "pipeline" is full).
5. Better cell "team" communications.
6. Fosters a beneficial employee "ownership" and "we can do" attitude.
7. Supports a demand "pull" operation. Yields much better material control and schedule control compared to traditional MRP-based "push" scheduling systems.
8. Much reduced risk of scrap generation caused by engineering changes or obsolescence.
1. Lower equipment utilization for "non-bottleneck" cell operations, unless multi-functional equipment is employed.
2. If there is no equipment redundancy within the cell, the whole cell may shut down when one piece of equipment goes down.
3. Loss of dedicated or centralized expertise for cells where one operator must operate several different pieces of equipment.
4. If demand falls and production output is below the planned cell capacity, per unit manufacturing costs tend to be higher with some cells. This occurs when a good labor balance cannot be achieved at the lower output level.
5. Any small subsequent changes in the production process or sequence can have major changes on the cell layout and cell efficiency. There sometimes is more flexibility when using traditional departmentalized layouts.
6. Some multi-product cells are not suitable for higher volume orders where they may become a bottleneck to scheduling other parts.

The writer has visited more than a few plants where the transition to lean manufacturing and cross trained cell teams has been curtailed or stopped altogether. there are some lessons is worth to be noted to avoid the same failure:
1. Need for support by shop-floor operators
2. Inappropriate production systems 
3. Fear of underused equipment due to archaic business models
4. Loss of interest due to poor initial implementation
When balancing the positives against the negatives, the lean approach benefits far outweigh the negatives for most companies. Just because there are negatives and costs associated with converting to cells is no reason or excuse not to make the conversion.


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