Type IV Relationship:

In this relationship, both non-bottleneck and the bottleneck resources supply directly in the market:

The bottleneck resource, whose rate is lesser than the market demand, is used at its 100% capacity. The non-bottleneck resource may be utilized at 100% only when the market demand enhance; otherwise it shall remain under-utilized.

Though all of the four relationships, following guidelines come out:

a. Use bottleneck at 100% capacity.

b. Underutilise non-bottleneck to remove the inventory pile-up.

c. The level of utilization of non-bottleneck is determined by the capacity of bottleneck and not by its own capacity. In the last (IV) relationship, this is driven by market demand.

d. Enforcing idle time on non-bottleneck and tolerating a sure level of inventory pile-up should have an optimal trade-off.

e. Throughput of the plant is restricted by the capacity output of the bottleneck resource (which is the constraint).

Thus, these rules suggest that the non-bottleneck must not produce more than the absorption capacity of bottleneck resources, otherwise there shall be enhance in inventory pile-up and the increasing in operating expenses. Hence, underutilisation of non-bottleneck is the only prudent strategy.