by R.T. “Chris” Christensen

Maintenance is the second bottleneck. What do I mean by that? And if maintenance is the second bottleneck, then just what is the first bottleneck? To understand the questions, we need to go back and determine just what a bottleneck is and why we have two of them.

By definition, a bottleneck is a function within the organization that serves as a pinch point in the flow of work. This can be a piece of equipment or manpower or, in some cases, even you. A bottleneck is, in essence, the most heavily loaded piece of equipment or person in your operation.

A bottleneck is a constraint that restricts the flow within the organization. That restriction can best be defined as an allocation of time. By this, I am saying that the bottleneck is a time constraint; what we have done is given more work to one area than there is available time to get the job done. That’s why we hear people say that there is just not enough time in the day to get the job done. We gave them too much to do and have overloaded their 24-hour clock.

While I am working to develop a clock stretcher, I have not been successful up to this point. Therefore, by definition, there are only, and exactly, 24 hours in a day. So then, when we say that we don’t have enough time to get the job done, what we are really saying is we have more work to get done than there are available hours.

From a production point of view, a bottleneck is the machine or workstation that has the highest amount of hours scheduled to be completed. Usually, we begin to overload a worksite when we approach around an 80 percent workload. The other 20 percent of the time is consumed in setup, scheduling problems, material problems, operator problems, container shortages and a myriad of other unplanned and non-forecastable problems that can crop up on the shop floor.

This then begs this question: Are bottleneck operations good or bad? Most people say they are bad. I feel differently.

I like bottlenecks to the extent that this means we are selling our products and have a lot of stuff to build. But how do you schedule the bottleneck in the overall shop sequence? It’s simple. You sequence the highest-loaded machine first and then the second-highest-loaded machine and so on down, prioritizing the schedule sequence based on load. Production control schedulers do this task.

From the maintenance side, you too have a bottleneck. This is the person or the craft or the piece of equipment that has the highest amount of work orders ahead of it. By random mix of the type of work orders, you just might have a heavy workload for your electricians for the next month and then this could shift from the electricians to the millwrights, and so on. In maintenance, your bottleneck can, and does, shift over time based on the mix of work to be done. This can also be seasonable. The clue here is to watch for the shift in your own bottleneck and schedule accordingly.

Now if you look at your operation, it is obvious that the most important use of time is in the production of something that you can sell. It is the value-added use of your 24-hour clock. That is what production control does. It schedules the value-added use of the 24-hour clock. It schedules the bottleneck. But what about your bottleneck?

Because there is only one clock, there can only be one person who can schedule the allocation of the time. It’s a fact of life. Production control must schedule the machine bottleneck, but it must also fit your maintenance bottleneck into the 24-hour clock to get the best use of the clock. Value-added use of the clock is the first scheduling priority in bottleneck scheduling. Maintenance scheduling is the sequencing of the second bottleneck into that same 24-hour clock. Your task then is to work closely with production control in the allocation of the work to get both bottlenecks scheduled together.

Value-added activities need top priority, but your second-level bottleneck needs to be completed, too. Without maintenance on the bottleneck, the equipment will not be able to produce value-added product. Therefore, maintenance must also be scheduled and completed so that the equipment is available for scheduling the production of value-added parts.

Do you work closely with production control in the scheduling of the maintenance 24-hour clock? If not, you really should.

R.T. "Chris" Christensen is the director of the University of Wisconsin School of Business' operations management program. If you have a question, contact Coach Christensen by phone at or e-mail . 

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