A Bottleneck is a term used about the step in a process that limits the output of the overall process, or the work in a production cell that have the longest cycle time.
Bottleneck Analysis for Capacity Planning
Bottleneck Analysis, which is one of the lean tools, should be done when planning a capacity expansion, as the process step which is the bottleneck need to be addressed first. Only improving the capacity to other process steps will not increase the overall process throughput, as they still will be limited by the bottleneck process step.
Problems with Bottlenecks
A bottleneck gives other problems as well, in addition to limiting the capacity or throughput of a process as discussed above.
Process Blocking: Process blocking can appear if the process prior to the bottleneck start filling up a buffer, as the following process can’t cope with the output quickly enough. If there no longer is space in the buffer, all upstream processes are forced to stop as a result. When this happens it is called process blocking.
Process Starvation: Process starvation is another problem bottlenecks can give, this is the scenario where the processes after the bottleneck are forced to stop when they don’t get material quickly enough.
Bottlenecks are usually easy to spot, as work piles up just before the bottleneck, and workers or processes after the bottleneck stand idle part of the time. E.g. the capacity of the line might be 200 parts an hour, but your bottleneck might only handle 50 parts an hour.
Maximize Bottleneck Capacity
Start with looking for ways to get more out of your bottleneck without adding any additional expenses. E.g. changing time of maintenance if it is due to machine downtime, or change the location of the input parts if they are inconveniently placed for the operator and slowing him down.
Amend Non Bottlenecks
When the bottleneck has been maximized, the other processes can be adjusted to that for a steady and smooth process flow. By reducing the speed of the upstream processes, it will reduce or eliminate the buffer zone and extra material handling which will free up staff. Matching the downstream with the bottleneck output will avoid waiting time.
When the other improvements don’t get the capacity your business requires, the bottleneck has to be increased. This is done by adding an additional machine, worker and so forth. But as this adds large on-going expenses to your business, it should only be considered after maximising the bottleneck doesn’t give the required capacity.
Monitor the Process
After implementations have been done, the process need to be reviewed for similar problems like materials piling up as seen in the beginning.
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