How do you use Pareto charts to prioritize quality issues in production engineering?

1 What is a Pareto chart?

A Pareto chart is a type of bar chart that shows the frequency or impact of different factors or categories on a quality problem. The bars are arranged in descending order from left to right, and a cumulative line is added to show the percentage of the total effect. The chart is based on the Pareto principle, which states that 80% of the results come from 20% of the causes. By using a Pareto chart, you can easily identify the most significant factors that contribute to your quality problem and focus your improvement efforts on them.

2 How to create a Pareto chart?

To create a Pareto chart, you must begin by defining your quality problem and the unit of measurement. For instance, you might want to reduce the number of defects or the amount of scrap in your production line. Then, collect data on the possible causes or categories of your quality problem. This could be done through a check sheet or a fishbone diagram to list the sources of defects or scrap in your process. Summarize the data and calculate the frequency or impact of each cause or category. After sorting the data in descending order and calculating the cumulative percentage of the total frequency or impact, draw a bar chart with the causes or categories on the x-axis and the frequency or impact on the y-axis. Additionally, add a line chart with the cumulative percentage on the secondary y-axis. Finally, draw a vertical line at 80% of the cumulative percentage to separate the vital few causes from the trivial many.

3 How to interpret a Pareto chart?

To interpret a Pareto chart, you need to look at the shape and position of the bars and the line. The bars that are on the left side of the chart and above the 80% line are the most important causes or categories of your quality problem. These are the ones that you should prioritize and address first. The bars that are on the right side of the chart and below the 80% line are the less important causes or categories of your quality problem. These are the ones that you can ignore or deal with later. The Pareto chart helps you visualize the relative importance and impact of each cause or category, and guides you to make data-driven decisions.

4 How to use a Pareto chart for improvement?

Once you have identified and prioritized the most important causes or categories of your quality problem, you can use a Pareto chart to plan and monitor your improvement actions. To do so, set a target for reducing the frequency or impact of your quality problem, such as reducing defects by 50% or scrap by 20%. Next, select and implement improvement actions that address the vital few causes or categories, such as using the 5 Whys technique or a root cause analysis. Then, collect and update the data on the frequency or impact of each cause or category after implementing the improvement actions. Redraw the Pareto chart with the updated data and compare it with the previous chart to show the improvement results. Finally, evaluate the effectiveness of your improvement actions and adjust them if necessary with a cost-benefit analysis or return on investment calculation.

5 What are the benefits and limitations of Pareto charts?

Pareto charts have several advantages for production engineering, such as helping to identify and prioritize quality issues, as well as communicating and presenting quality problems and improvement actions. Additionally, they can be used to measure and monitor quality improvement progress and results objectively and quantitatively. However, Pareto charts also have some limitations. Accurate and reliable data collection and analysis can be time-consuming and costly. Furthermore, they do not show the causal relationships or interactions between the causes or categories of your quality problem, nor do they provide solutions or recommendations for your quality issue.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?