Keywords: bottleneck, short-term bottleneck, log-term bottleneck, identifying bottlenecks
In production and project management, a bottleneck is one process in a chain of processes, such that its limited capacity reduces the capacity of the whole chain. The result of having a bottleneck are stalls in production, supply overstock, pressure from customers and low employee morale. There are both short and long-term bottlenecks. Short-term bottlenecks are temporary and are not normally a significant problem. An example of a short-term bottleneck would be a skilled employee taking a few days off. Long-term bottlenecks occur all the time and can cumulatively significantly slow down production. An example of a long-term bottleneck is when a machine is not efficient enough and as a result has a long queue.
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| Example illustration of a bottleneck in a manufacturing material flow |
An example is the lack of smelter and refinery supply which cause bottlenecks upstream.
Another example is in a surface-mount technology board assembly line with several pieces of equipment aligned. Usually the common sense is driven to set up and shift the bottleneck element towards the end of the process, inducing the better and faster machines to always keep the PCB supply flowing up, never allowing the slower ones to fully stop, a fact that would be heeded as a deleterious and significant overall drawback on the process.
Identifying bottlenecks
Almost every system has a bottleneck, even if it is a minor one, if every system was running at full capacity, at least one machine would be accumulating processes. Identifying bottlenecks is critical for improving efficiency in the production line because it allows you to determine the area where accumulation occurs. The machine or process that accumulates the longest queue is usually a bottleneck, however this isn't always the case. Bottlenecks can be found through: identifying the areas where accumulation occurs, evaluating the throughput, assessing whether each machine is being used at full capacity and finding the machine with the high wait time.
Accumulation
When input comes in faster than the speed of the process, accumulation starts to occur. This means that the machine either does not have enough capacity, is not being fully utilized (inefficient in use) or has an under-qualified operator. This method is not effective at identifying bottlenecks where the queues are at several process steps, as there are multiple processes with accumulation.
Throughput
Since the production line is directly linked to the output of the machines, it allows for the identifying of the main bottleneck in the manufacturing process. In changing each machines throughput, it will be possible to assess which machine affects the overall output the most, and hence determine the bottleneck in the chain of processes.
Full capacity
By using the utilization percentage of each production unit, it is possible to determine the machine which uses the highest percentage of its capacity. This machine is bottlenecking the other machines by 'forcing' them to operate at a lower capacity. However, if all machines in the chain of processes are running at a similar capacity level, increasing the capacity of the lowest machine will not create a significant improvement to the total output.
Wait times
In the case where several production units are already running at full capacity, tracking the down time of machines will allow you to identify which machine is being bottlenecked. Usually the machine prior the machine with the highest wait or down time in the chain of processes is a bottleneck. The result of this is a machine being under utilized. Read more...
