In production and project management, a bottleneck is a 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.^[1] 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.^[2]

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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 strategy is to set up and shift the bottleneck element towards the end of the process, inducing the better and faster machines to always keep the printed circuit board (PCB) supply flowing up, never allowing the slower ones to fully stop; a strategy that could result in a deleterious (or damaging) and significant, overall drawback in the process.

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.^[3] 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.^[4][5]

The consequences of having bottlenecks in production are possible stalls in production, supply overstock, fall in employee morale, and loss of customers. Bottlenecks can result in the overloading of a machine. Overloading a machine can lead to the machinery getting damaged or worn out, and the result of this would be potential stretches of downtime in the long term.

Once the bottleneck has been identified, assessing the degree of the bottleneck is crucial for determining how to manage the bottleneck. The bottleneck could be either minor or severe. Minor bottlenecks may not need to be immediately addressed, whereas severe bottlenecks should be dealt with immediately. There are several ways to eliminate bottlenecks. Some means of doing so are: Adding resources to the bottleneck operation (more people),^[8] minimising downtime,^[9] eliminating non-value activities, investing in more machinery which completes the same action, and optimising the bottlenecks operation.^[10][11] Other sources similarly suggest that once the bottleneck has been identified it is best to ensure it is well maintained,^[12] to provide a constant buffer stock upstream of the bottleneck, to reduce time wasted in set ups and changeovers, and to train more operators for the bottlenecked machines.^[13][14] These are further explained below. Having production scheduled to optimise efficiency, is another means of effectively utilising the bottlenecked machine. This minimises the possibility that the production quota will not be met. Scheduling also reduces the number of situations where production is halted due to a lack of personnel, due to increased organisation and greater planned out production. It also allows for the full advantage of the time available to be taken, as pockets of time can be found to keep the machine running for as many hours as possible in a week.^[15]

Preventing bottlenecks would be ideal to avoid having to manage and resolve them in the future. There are ways to work around them when planning the production environment. Giving employees free rein over minor decision making, will allow them to make the decision they feel is most efficient, and being operators of the machine, their experience will allow them to become specialised in the use of the machine over time.^[18] Cross-training employees will increase adaptability in the production line and therefore reduce potential downtime in the future. Hiring high performance employees will reduce the possibility for bottlenecks to be formed by underperforming employees who are inefficient at using their assigned machinery.^[19] Planning for a higher potential output when designing the production environment is crucial in the long run, for occurrences of larger orders when there is need to run all the machinery. Having all the machinery running at full capacity is not always ideal, due to situations where malfunctions occur and production is halted. Having inspiring leaders who have a strong understanding of how to keep production running smoothly, will allow greater control of all the different processes in the chain of production. Taking into account the layout of the different processes, can also increase efficiency as it minimises delay caused in the transportation stage. The use of a proper layout can reduce the overhead of machines and can reduce material handling time.^[20]

Establishment of standardized exchanged protocols, can minimise the potential for future bottlenecks to occur through minimising down time. This increases efficiency by reducing any potential confusion between different sectors and hence reduces the possibility for delays of the arrival of raw materials.^[21]

A static bottleneck is where no random or unexpected fluctuations (such as those that would happen during either a changeover or a breakdown of the system) occur. A static system does not change in behavior and hence the system stays constant. Finding a bottleneck in a static system is very simple, it is simply the machine or process with the longest constant cycle time. Static systems do not exist in reality as no matter what, there will always be a slight fluctuation in cycle time. This is because there is no way to prevent all fluctuations from occurring to slow the system down. An example of this could be a power shortage or a natural disaster.^[22] The behavior of any system is vulnerable to any random event and hence all systems are dynamic. Dynamic systems can be divided into two main groups: Stable and unstable. The significant difference in the context of dynamic systems, is that the bottlenecks can shift. The speed of which a bottleneck shifts depending on the buffer between the processes.^[22] Bottlenecks shift when the location of the work center in the production area changes, and this leads to control problems due to the significant delay in output. Shifting bottlenecks are a result of inevitable, unexpected events, for which no planning is possible.^[23]

The steps suggested to avoid or prevent shifting bottlenecks are:

Step 1) Re-evaluate the maximum load of every machine, process or work center when accepting a new order.

Step 2) Find the bottleneck in the system and identify its surplus capacity.

Step 3) Fill the bottlenecks surplus capacity.

Step 4) Find out the release time of the material as a result of the new bottlenecks scheduling.

Through following these steps, the order production will be completed in the shortest possible time frame.^[24]

• Critical path method
• Theory of constraints