Lean Problem Solving Tools

February 1, 2006
By Darren Dolcemascolo

While most people associate lean with tools and principles such as value stream mapping, one-piece flow, kanban, 5S, total productive maintenance, and kaizen events; few people think about the more mundane aspects of lean. Problem solving is one of the keys to successful lean implementation through worker empowerment.

Let's look at what problem solving is about. We'll begin by asking the question: "What is a problem?"

A good definition of a problem is a variation from a recognized standard. In other words, you need to know how things “ought to be” before you can recognize a possible cause for them not being that way.

After a problem has been recognized, a formal problem solving process should be applied. We will cover two of the most basic tools for problem solving: The Five Why's and The Fishbone Diagram.

The Five Why's

The 5 Whys is a technique that doesn't involve data segmentation, hypothesis testing, regression or other advanced statistical tools, and in many cases can be completed without a data collection plan. By repeatedly asking the question "Why" at least five times, you can peel away the layers of symptoms which can lead to the root cause of a problem.

Here is a simple example of applying the 5 Why's to determine the root cause of a problem. Let's suppose that you received a large number of customer returns for a particular product. Let's attack this problem using the five why's:

1. Why are the customers returning the product?

Answer: 90% of the returns are for dents in the control panel.

2. Why are there dents in the control panel?

Answer: The control panels are inspected as part of the shipping process. Thus, they must be damaged during shipping.

3. Why are they damaged in shipment?

Answer: Because they are not packed to the packaging specification.

4. Why are they not being packed per the packaging spec?

Answer: Because shipping does not have the packaging spec.

5. Why doesn't shipping have the packaging spec?

Answer: Because it is not part of the normal product release process to furnish shipping with any specifications.

Using the five why's in this case revealed that a flaw in the product release process resulted in customers' returning of a product.

The Fishbone Diagram / Cause and Effect Diagram

The Cause and Effect Diagram or Fishbone Diagram is a graphical tool for identifying the relationship between a problem and its potential causes. One of the most effective ways of constructing such a diagram is to brainstorm potential causes in a team environment. For example, a cause and effect diagram might be used to determine possible causes of a recurring defect in a manufacturing process.

The Fishbone diagram is drawn to resemble the skeleton of a fish, with the issue (problem or process condition) on the right side. The major cause categories are written in the boxes on the left side of Cause and Effect Diagram. Summarize the major causes under the categories. These categories are usually Methods, Machines, Materials, and People. Sometimes, other categories such as Measurements and/or Environment are added.

Cause and Effect

Under each category, identify potential causes for the problem relating to the category. For example, if the fact that incorrect parts are being delivered to the assembly is a potential cause for the problem being addressed, that would be listed as a branch under "Materials."

Both Fishbone Diagrams and the Five Why's are simple, very useful methods for problem solving. One of the first steps to creating a lean culture is to turn every employee into a problem solver. This should begin with teaching the use of "The Five Why's" on a regular basis.

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