As the name itself suggests, a bottleneck resource is an obstacle to smooth flow in a process.
Consider this process made of five resources R1 to R5.
Resources can be machines, test equipment, ovens, paint shops, and so on. Each resource has its own processing capacity and in a process made of heterogeneous resources, chances are that every capacity is different.
In the diagram* the resource capacity is the aperture of its drain, not the storage capacity which is inventories’ or buffers’ capacity.
*this diagram’s credit goes to Philip Marris, founder and owner of Marris Consulting. A similar diagram is printed on the cover of Philip’s book, one I learned a lot with. Philip and I meet periodically for a chat in Paris, France.
Human resources can be bottlenecks too.
Consider the flow (blue liquid). The global performance (liquid throughput) of the process is limited by the least capacity within the process, which is obviously R3.
The bottleneck betrays itself with huge accumulation in front of it (raw material, parts, crates, orders, files…) and low throughput letting the next resources in the process waiting most of the time.
R4 and R5 could let much more flow through them but they keep being starved by the limited output of R3. R1 and R2 also have bigger capacities than R3 and there is no choice than to store their output in front of R3, or stop R1 and R2 until R3 caught up.
A bottleneck resource is a real bottleneck when its capacity is, in average, lower or equal to customer’s demand. A true bottleneck runs 24 hours 7 days a week and still cannot supply what is required. Conversely a non-bottleneck has excess capacity in regard of demand.
A bottleneck is usually very expensive and/or difficult to get. If this is not the case, the solution is obvious: buy additional capacity!
As a true bottleneck cannot be duplicated that easily, its capacity has to be used very wisely. As the bottleneck resource’s capacity constrains the whole process, this resource is very precious and none of its scarce capacity must be wasted.
The Theory of Constraints (ToC) proposes rules to manage such peculiar resources.
These rules can be found here:
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