In a perfectly balanced plant. the output of Stage 1 provides the exact input requirement for Stage 2, the output of Stage 2 provides the exact input requirement for Stage 3, and so on. In practice, however. achieving such a "perfect'' design is usually both impossible and undesirable. One reason i-, that the best operating levels for each stage generally differ. For instance, Department I may operate most efficiently over a range of 90 to 110 units per month while Department 2. the next stage in the process. is most efficient at 75 to 85 units per month, and Department 3. the third stage. works best over a range of 150 to 200 units per month. Another reason is that variability in product demand and the processes themselves generally lead to imbalance except in automated production line.
which, in essence, are just one big machine There are various ways of dealing with imbalance. One is to add capacity to those stages that are bottlenecks This can be done by temporary measures as scheduling overtime leasing equipment or going outside the system and purchasing additional capacity through subcontracting A second way is through the use of buffer inventories in front of the bottleneck stage to assure that it always has something to work on. A third approach involves duplicating the facilities of that department that is the cause of the bottleneck (which, in essence, eliminates the bottleneck)