Goldratt's Theory of Constraints
A. 9 OPT principles (optimized production technology)
- Balance flow, not capacity.
- Utilization of a non-bottleneck is determined by some other constraint
in the system, not by its own potential.
- Utilization and activation are not synonymous a. utilization refers
to running the resource in accordance with the rate at the bottleneck.
b. activation is running the machine whether it is contributing to throughput
- An hour lost at a bottleneck is an hour lost for the entire system.
- An hour saved at a non-bottleneck is a mirage. (just adds to excess
- Bottlenecks govern both throughput and inventory.
- The transfer batch size may not, and many times should not be equal
to the process batch size.
- The process batch should be variable, not fixed.
- Schedules should be established by looking at all the constraints simultaneously.
Lead times are a function of the schedule, do not assume they are fixed.
B. OPT scheduling procedure - 3 steps
- Identify the bottlenecks
- Schedule and operate to see that the bottlenecks are fully utilized.
- Schedule the non-bottleneck operations to keep bottlenecks supplied
and yet hold WIP inventory low.
-OPT is a computer program similar to MRP used to schedule operations
and control inventory. It seems to be especially useful when product mix
and level of demand vary considerably.
C. Theory of Constraints
1. Three kinds of constraints
- internal resource constraints
- market constraints
- policy constraints
2. The 5 step procedure for continuous improvement is:
1). Identify the constraint (s)
2). Decide how to exploit the constraint
3). Subordinate everything else to the constraint
4). Elevate the constraint
5). WARNING: If in step 4 the constraint is eliminated, do not let inertia
become the new constraint.