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Bottleneck / Capacity Constraint (Part 2)

Just remember: If something is not really a bottleneck, creating more capacity will not speed up your whole system. That point deserves some more attention.

If you speed up a non-bottleneck, the speed of your whole system will be unchanged!

Think of this like a team of horses pulling a stagecoach. You will go at the speed of the slowest horse. If you make one of the fastest horses quicker, you will still travel at the speed of the slowest horse!

Here are some basic rules when dealing with bottlenecks:

  1. NEVER starve a bottleneck. Do whatever you can to make sure bottlenecks do not stop production. The best way it so improve the upstream process to make it more reliable. A not-so-great way is to add a buffer in front of the bottleneck. While this violates lean principles, it can be an effective short-term measure. Just make sure you don’t let it become long-term. (Side note: I have rarely seen a short-term measure that did not become permanent.) Use buffers with caution.
  2. NEVER let a bottleneck wait for repairs. Pull your maintenance team off other projects if a bottleneck process goes down for maintenance issues. Bottlenecks don’t have the catch-up speed of other processes.
  3. Bottlenecks should be on your kaizen list. You should be spending a disproportionate amount of your productivity or delivery improvement effort on bottlenecks. Remember, though, quality should trump cost and delivery when selecting projects.
  4. Minimize setup time on bottlenecks. Keep in mind that this means to reduce setup time, not to do bigger batches of each product.
  5. Pace your line to the bottleneck. Use your bottleneck to determine if your operation can meet your customer demand.
  6. Don’t confuse external problems with a step being a bottleneck. Any process that is starved of raw materials will shut down. Make sure you are judging processes under normal production conditions.

From a job satisfaction standpoint, bottlenecks frequently cause rifts on a team. One station on an assembly line may be a bottleneck, and constantly fall behind, causing the whole team to stay late. Make sure you assess this problem and explain that the problem is the process and not the people.

The Goal’ by Eliyahu M. Goldratt gives a great deal more information on this subject. He refers to this as the Theory of Constraints. His teachings are told in a narrative that describes the efforts of a plant manager to turn his plant around, making it a very easy and enjoyable read.

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If you want to improve the output of the system, you can only do so by getting more through your bottlenecks.

Your first task is to identify these constraints. When your demand is well below the capacity of your bottleneck, it might be hard to find. Most people uncover their bottlenecks though, when demand rises past the point of the weak link can keep up.

A disproportionate amount of your management effort should be spent on your bottlenecks. Any improvements you make on a non-constraint will do nothing for your total output. Most managers can easily recognize that the system can be improved by increasing the capacity of the slow machine or process.

Season leaders, though, will see that variation on upstream processes can be just as harmful. That’s because fluctuations in the supply of components and raw materials shuts down a bottleneck just as quickly as a malfunction does.

  • A system can only produce as much as its bottleneck.
  • You will always have a weakest link. Once you strengthen it, the second weakest link takes the title.
  • Variation and intermittent problems can cause a bottleneck to migrate. These migrating constraints can be extremely challenging to resolve.
  • Use facts and data to be sure you correctly identify your bottleneck.

Which of the following statements is most true about your bottleneck?

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