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Unit 4: Process Selection and Facility Layout

Disadvantages include the following: Notes
1. Reduced manufacturing flexibility.
2. Unless the forecasting system in place is extremely accurate, it also has the potential to
increase machine downtime (since machines are dedicated to cells and may not be used all
the time).
3. There is also the risk that the Cells that may become out-of-date as products and processes
change, and the disruption and cost of changing to cells can be significant.
4. There is increased operator responsibility, and therefore behavioural aspects of
management become crucial.

4.9 Combination Layout

With increasing pressure on manufacturing flexibility to meet customer needs, there has been a
move towards new forms of assembly lines, e.g., mixed model lines. A mixed-model line
produces several items belonging to the same family, such as the different models of cars
manufactured by Maruti Udyog Ltd. In contrast, a single-model line produces one model with
no variations; mixed-model production enables a plant to achieve both high-volume production
and product variety.

This approach is also used by JIT manufacturers such as Toyota; its objective is to meet the
demand for a variety of products and to avoid building high inventories. Mixed-model balancing
is carried out by Toyota Motor Corporation by averaging the production per day in the monthly
production schedule classified by specifications, and dividing by the number of working days.
The production sequence during each day, the cycle time of each different specification vehicle
is calculated. To have all specification vehicles appear at their own cycle time, different
specification vehicles are ordered to follow each other.
This does complicate scheduling and increase the need for good communication about the
specific parts to be produced at each station. Care must be taken to alternate models so as not to
overload some stations for too long. Despite these difficulties, the mixed-model line may be the
only reasonable choice when product plants call for many customers' options, as volumes may
not be high enough to justify a separate line for each model.

4.10 Other Service Layouts

Warehouse or Storage Layout

Warehousing was supposed to disappear with Lean Manufacturing. This has rarely occurred but
the nature of warehousing often does change from storage-dominance to transaction dominance.
In addition, the trend to overseas sourcing has increased the need for warehousing and its
importance in the supply chain.

Warehousing buffers inbound shipments from suppliers and outbound orders to customers.
Customers usually order in patterns that are not compatible with the capabilities of the warehouse
suppliers. The amount of storage depends on the disparity between incoming and outbound
shipment patterns.
One key to effective design is the relative dominance of picking or storage activity. These two
warehouse functions have opposing requirements.

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