THEORY OF CONSTRAINTS
It is a problem solving process which focuses on the elimination or streamlining of weakest link in the chain of processes. Usually the weakest link is constraining itself. The beauty of theory of constraints lies in a fundamental, stated as, Overall process cannot be improved without entertaining the weakest link first.
It includes five step methodology to deal with encountered situation,
Drum-Buffer-Rope Approach
In 1997 Goldartt went one step further by drilling third step (Adjust) down to the basic niches as a below subjected approach.
It is defined as To avoid long lead times & excess WIP, all system processes should be slowed down (via rope) to the speed of the slowest process (the drum) , and the amount of WIP (buffer: length of rope) is determined by the performance or capability of individual processes.
Consider a squad of soldiers walking in single file as an analogy for a string of production processes. As the first soldier moves forward, he received unprocessed material, the fresh ground. Following that soldier, remaining squared move over the ground (once fresher) to transform into a desired output.
Thus, individual processes are moving over the fixed material rather than the other way around.
In this system, the constraint will be slowest soldier. As the later process cannot be performed until formal ones are done, similarly a process step which is resulting in a slow output must be tackled ASAP.
TOC & Business Measures
Cited from the Donald & Kubiak work, The TOC as described by Goldratt has significant impact on three key interdependent operating measures of a business.
Throughput– The rate at which entire system generate money via sales.
Inventory– The money the system invest in things it intends to sell
Operating Expense– The money the system spends in transforming inventory to throughput.
All the three key measure are directly & indirectly proportional to each other (shown as arrow direction)