Bottleneck Analysis – What and When?

A bottleneck is any point where the output of one area is building up in another area nearby. It constrains the ability to process goods or services according to plan. Think of it as the weakest link. That part is simple. You may also hear them called “constraints,” like the Theory of Constraints. No matter what you or anyone else calls them, bottlenecks are problems that need to be resolved as quickly as possible. They work directly against the idea of Just in Time (JIT) and cause issues that result in needed parts storage and supply. In a nutshell, they mean someone isn’t getting what they need when or where they need it.

Left unchecked, the bottleneck will set a new Takt time for your process, whether you like it or not. Forget all the work that went into determining the Takt time, because the bottleneck, or constraint, will redefine it and take over.

In the worst situations where nothing is being done to fix a bottleneck, the ripple effects can reach the entire process all the way through to delivering the final product to the customer. At the very least, the people in immediate area will feel the effects. That can lead to other issues, like wasted time and a lack of engagement or confidence in the work. Once those sentiments take hold, they’re hard to change.

What is Bottleneck Analysis?

Now that we’ve painted a pretty grim picture of how a bottleneck can affect your production floor, let’s switch gears to focus on something that could help – bottleneck analysis. As you might guess, this is the process of investigating a bottleneck and determining how to smooth it out so the operators can get back into the flow of working efficiently. That’s better for everyone, including the end customers.

When to use bottleneck analysis

This is also an obvious answer. Use bottleneck analysis when you have a bottleneck. There are two main telltale symptoms that will indicate there’s a bottleneck somewhere. When these show up, it’s time to dig into what’s causing them.

1. People are standing around waiting for parts they need to do their jobs (demand is higher than capacity)
2. Piles of a certain part are waiting to be used (demand is lower than capacity)

Key tools in Bottleneck Analysis

Something needs to be done about bottlenecks, the sooner the better, and the next steps can be clearer than they might seem at first. Here a two tools to get you started.

Theory of constraints (TOC): A method for finding the constraint, testing it, and improving it.

1. Identify the constraint: Again, look for those signs, or talk with the person who raised the concern. The people closest to the bottleneck will have helpful information and may also have ideas for how to resolve whatever is causing it.
2. Exploit the constraint: Don’t let it stop for any reason. This will produce the effects consistently and make them easier to observe. Ideally, this step won’t take very long.
3. Subordinate to the constraint all other steps in the process: Let the constraint set the Takt time for the rest of the process. Observe what else needs to change in order to match that Takt time and evaluate what that means for the rest of the line.
4. Elevate the constraint: In this case, “elevate” means to improve the process at the constraint, or bottleneck. Do this as quickly as possible to reduce the number of mistakes.
5. Repeat the TOC process: Making improvements at one point in the process will probably cause a bottleneck at another point, so be ready to repeat this process until the whole line is improved. Clear communication channels, both from the project team to the other operators and vice versa can streamline how the improvements are identified and implemented. It can also prime everyone’s brain to notice when they may be seeing an effect of the bottleneck or improvements. Communication is key to reducing frustration and rumors.

DMAIC: A five step methodology that relies on data to improve a process.

1. Define your project.
2. Measure the process activities, effects of the bottleneck, and the process’s ability to meet the established specifications.
3. Analyze the data you’ve collected to find the root cause. (Helpful tools: Root Cause Analysis, Failure Mode and Effects Analysis, or a Multi-vari chart)
4. Improve the process by finding ways to remove the root cause, or causes. (Helpful tools: Design of Experiments and Kaizen events)
5. Control the improved process and monitor the performance, including tools like 5S and Poka-yokes.

Finding the bottleneck is just the first step in all of this, but it is critical. The chances of finding it sooner rather than later are better if you’ve already created a work environment built on trust and an honest interest in improvement. Once the improvements are made, remember to recognize the people who made them possible and the people who sustain them or who make further improvements.