Manufacturing ERP Software
How to Use a Causal Chain, Part 1

How to Use a Causal Chain, Part 1

By Bob Sproull

In this new series, I will present and examine a problem-solving tool referred to as the causal chain. I have used the causal chain to solve many problems and will provide a pertinent example in this post.

Much of what I will discuss in this series is taken from my soon-to-be-published book, The Problem-Solving, Problem-Prevention, and Decision-Making Guide: Organized and Systematic Roadmaps for Managers..

Presenting a model to trace causes back to their root

When problems occur, we know that a chain of events has taken place to alter the performance of the process. We aren’t always certain as to what happened, so we need some kind of tool or technique to help us develop a theory as to what occurred. One of the most effective tools available for accomplishing this is the causal chain.

Causal chain diagrams show a stepwise evolution of problem causes. Each step represents an object in either a normal or abnormal state. The object is placed on the line to the far right of the chain with its status listed directly beneath it. So, in Figure 1, the object in distress is the press and its status is that it has stopped. Although we might use a cause-and-effect diagram to list the variety of reasons why the press stopped, that would not explain the causal mechanism that triggered the stoppage.

Causal Chain Diagram

Figure 1

The question that guides the causal chain process is, “Why?”

In Figure 1, we see that a press has stopped and we ask the question “Why?” The press stopped because the motor stopped. Why did the motor stop? Because the current has stopped flowing.

We continue asking “Why?” until we reach the end of our chain, and find that the press stopped because the motor stopped, because the current stopped, because the pressure switch opened, because the air pressure was too low, because the air compressor failed, because the oil level was too low, because of a gasket that failed. We have now developed a potential theory or model as to why the press stopped. In the process, we have identified objects or items (e.g. current, oil level, etc.) that we can test to prove or disprove our theory. Each step in the diagram is the cause of the next step, and the effect of the preceding step. That is, the information on the step to the left is always the cause of the information on the step to the right.

What if we have more than one potential cause? How do we handle that situation? The answer is simple: we create additional individual chains. Each chain we create represents a brief theory to prove or disprove as to how the core machine was malfunctioning.

Coming in the next post

In the next post, I will explore examples of multiple-chain causal diagrams.

Until next time.

Bob Sproull

The Problem-Solving, Problem-Prevention, and Decision-Making Guide: Organized and Systematic Roadmaps for Managers, Bob Sproull, Productivity Press, 2018

Bob Sproull

About the author

Bob Sproull has helped businesses across the manufacturing spectrum improve their operations for more than 40 years.

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