Eliyahu M Goldratt’s Theory of Constraints (TOC) states that the bottleneck in a work system is the crucial constraint that must be scheduled first in order to achieve maximum system output. All efforts are to go toward scheduling the bottleneck work center, the capacity of which does not meet the demand placed on it and is less than the capacity of all other work centers. TOC uses five steps (Godratt, 1999, p. 3-6), including:
Identify the bottleneck. 2. Exploit the bottleneck, maximizing its throughput by streamlining or improving processes, equipment maintenance, training, anything necessary. 3. Subordinate the throughput of all other work centers to the bottleneck. 4. Elevate the status/condition of the bottleneck with additional equipment, staffing, work hours, etc. 5. Inertia is to be avoided. Begin again with Step #1, find the new bottleneck, and continue the 5 steps.
One scheduling alternative is to streamline and reduce the amount of setup time needed for the bottleneck. Another is to schedule its activity for additional hours per day and/or days per month. Further, breaks, lunchtime, and intermittent maintenance may be eliminated or rescheduled. Finally, work that does not need to go through the bottleneck can be eliminated by scheduling it to other work centers. MINPRT: Minimum Processing Time is the best scheduling rule to use in order to eliminate a bottleneck.
Applying this rule, each next-scheduled job is the one that has 2 the shortest processing time. Since all scheduled jobs are then the shortest jobs, more jobs are completed more quickly so that downstream work centers do not wait for work. Non-bottleneck work centers can be scheduled to include completing their setup after the bottleneck is set up, to use them fewer hours per day and/or days per month, and to schedule them for jobs that do not need to go through the bottleneck.
MINSOP: Minimum Slack time per Operation is a scheduling rule that can work well for non-bottlenecks. Using this rule, each next-scheduled job is the one that has the least slack (down) time so that production increases per hour. MINDD: Minimum Due Date may be the best option for non-bottlenecks and includes consistently scheduling the next job that is due first in order to meet due dates effectively. REFERENCES Goldratt, E. M. (December 1999). Theory of Constraints. Great Barrington, MA: North River Press.