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Bottlenecks / Capacity Constraints (+MP3)

The term ‘bottleneck’ (capacity constraint) comes from the area at the top of the bottle that limits the flow coming out. It doesn’t matter how big the rest of the bottle is—liquid will only flow out as fast as the size of the neck will allow.

A system is only as fast as its bottleneck process

A system is only as fast as its bottleneck process.

That is stating the obvious, but the concept holds true in any production environment, whether in the office, or on the manufacturing floor. There is one process, station, step, etc. that is the limiting factor that will prevent greater throughput. This is the rate limiting step that determines your capacity.

The power of knowing your bottleneck is considerable. It lets you increase your flow by improving one process, rather than your whole value stream. The reverse is also true. If you have a bottleneck, nothing you do anywhere else in the value stream will improve your throughput.

Keep in mind that the bottleneck may be unknown if demand is less than the capability of the slowest process.

Bottlenecks come in a great many forms. It may be the long cooking time in a bread oven. It may be the limited capacity on a truck that transports product around a corporate campus. It may be the approval process for a capital purchase.

Regardless of where your bottleneck it, if you want to increase the output of your whole system, you have to increase the capacity of your bottleneck.

This is an area where continuous improvement efforts shine. A machine that acts as a bottleneck may have a variety of different approaches that can resolve the issue.

  1. Six Sigma can help resolve quality problems, if there is a low yield (percentage of good parts) that is contributing to the problem. Imagine you need 80 units per day from a machine, that has an 80% yield and the capacity to make 100 total parts per day. It will produce 80 good parts and 20 defects. If demand rises to 90 per day, the machine becomes a bottleneck. You can reach your goal by buying another machine or improving yield to 90%. Which sounds less expensive?
  2. Setup reduction can make the machine available for a greater portion of the day.
  3. Lean efforts can improve the efficiency of that machine or process. Or it can improve an upstream process that feed it.
  4. Total Productive Maintenance can help resolve maintenance issues that slow production.

Here’s the frustrating thing about bottlenecks–once you resolve the issues around a bottleneck, and raise your production rates to meet demand, guess what happens: you will strain the next slowest process, creating a brand new bottleneck!

Even if your new bottleneck can meet the higher demand, you will ALWAYS have a bottleneck. There is always going to be a slowest step. Your demand may be below the capacity of the slowest process, but if demand rises, the bottleneck will be exposed.

On occasion, a bottleneck will jump around if the capacities of a few processes are similar. Normal variations in processes can make a bottleneck appear to jump back and forth between your slowest procedures. These situations tend to be a little tricky to resolve, as there is no clear culprit that is slowing down the works. Just go about the procedures below on the machines you most suspect of being bottlenecks.

Visit part 2 to continue reading about bottlenecks.

  • Never let a bottleneck starve. Because it is your slowest step in a process, it doesn’t have catch-up speed to get your system back on track.
  • Be careful about moving bottlenecks. With excessive variation and intermittent problems, bottlenecks may shift between various machines or processes.
  • Don’t guess at your bottlenecks. Use facts and data to determine where it actually is.

If you are working at a bottleneck operation, expect a higher level of scrutiny. That’s because the pace of the whole system is dependent upon you keeping your bottleneck operating. You are essentially operating without a safety net, so you will have no way to get back on track if you fall behind.

Pay special attention to maintenance issues that can cause you to lose production time. Also make sure that any signals you have upstream operations are sent properly. 


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