Process Bottleneck and process starvation

A bottleneck is commonly referred to step in a process which limits the total capacity of the process. It is the step, workstation, or stage which causes work in progress to build-up because it cannot be processed at the same rate as the other steps or workstations or has the greatest cycle time in a one path process. Bottlenecks should be identified and addressed when planning capacity expansions or planning the capital expenditure budget. Potential process bottlenecks should be investigated in production planning, and new facility planning. This can be achieved through preventive risk thinking and other problem analysis tools.

A simple example of a bottleneck can be observed below in Fig1:

                        Fig1: Bottleneck in a process.

As can be seen in Fig 1, the bottle neck in the process is process step 2 because it has the longest cycle time among the different steps. Between process step 1 and process step 2 there is a WIP or work in progress buffer. This is where inventory accumulates because it cannot be processed at the same rate it is produced or supplied to this step.

Bottlenecks not only slow or limit the capacity of a process but also cause to other problems in a process which are:

-Processing Blocking: this occurs when there is no more room to store WIP or buffer stock before the bottleneck process. This will cause the production line to bank up and stop until the WIP is cleared or processed. In the example above process can become blocked when the WIP area cannot take any more material until process step 2 processes some.

-Process Starvation: this occurs when the steps after the bottleneck step are forced to stop or idle because of no material process until the bottleneck process can supply materials to this next step. In the example above process step 3 can become starved because its cycle time is less than the previous step (step2) and will be forced to idle while it waits for materials or WIP. This limits the capacity utilization of the whole process.

       More lean concepts and terms