Tech Notes

Pareto Chart Analysis | Multi-Level Pareto Charts

Traditional Pareto charts visually display defect codes and causes in a simple, easily understood bar chart format. Because of their simplicity, Pareto charts have not been considered powerful analysis tools in manufacturing. That has changed with the exclusive ProFicient Multi-Level Pareto chart. Imagine displaying defect codes on a Pareto chart, but sorting and displaying them by shift, customer code, employee, lot number, part or any other descriptor that has been tagged to the data.

The ProFicient Multi-Level Pareto Chart is a robust and sophisticated attributes data analysis tool that transforms the stodgy traditional Pareto chart into a problem-solving and analysis powerhouse.

Traditional Single-Level Pareto Charts

Assume that a final visual inspection is being performed on an engine assembly. Defects are counted, categorized and entered. The result is a traditional single-level Pareto chart as found in Figure 1. The chart clearly shows that Incorrect Torque is the most prevalent defect.

To create a traditional Pareto chart with InfinityQS, go to the menu bar, click Chart | New, and make the appropriate selections in the Chart wizard. In the Chart Type window, choose "Pareto Chart" from the "CHART CATEGORIES" drop down list. Pareto charts can be created for Process Actions data or for Sampled Data.

Figure 1: Traditional Pareto Chart of Engine Defects


Multi-Level Pareto Charts

In addition to the PartProcess and Test names that are needed to create a chart within ProFicient, descriptors can optionally be tagged to any entered data. Once data is entered, the system allows sorting on any of the descriptors. In the example above, engineers might want to know which engine serial numbers(descriptor) had a specific type of defect.

To view the serial numbers by defect code, clickChart>Configuration>Processing. This brings up the Processing Options window found in Figure 2. In the "Major Category" tab, click "Defect Code." In the "Minor Category," tab, click "Descriptor." Next, select "Serial Number" (or your choice of descriptors) from the "Descriptors" portion of the window.

Figure 2: Pareto Chart Processing Options Window

The result is a Multi-Level Pareto chart as found in Figure 3. Optionally, the Processing Options window can be accessed by right-clicking on the Pareto chart and selecting "Processing" from the pop-up window.

Figure 3 shows how many "Incorrect Torque" defects occurred on specific engine serial numbers. Yellow bars represent the total number of defects for each defect code while blue bars show the amount from each individual serial number. When added, the number of defects from the blue bars makes up the total defects in the yellow bars above.

Multi-Level charts display a Pareto chart within a Pareto chart, allowing two-dimensional viewing of defects and their origin. Multi-Level Pareto charts provide significantly more information to users than traditional Pareto charts.

Figure 3: Multi-Level Pareto: Defect Code by Serial Number.


More on Multi-Level Pareto Charts

Engineers may want to know the type of defects found by serial number (the inverse of what is displayed in Figure 3). To do so, bring up the Processing Options window and in the "Major Category" tab, select "Descriptor" and "Serial Number." Then, in the "Minor Category" tab, select "Defect Code." The result is the Pareto chart found in Figure 4. This Pareto chart example contains the same data, but the orientation has been reversed such that the total number of defects for each serial number is shown on the yellow bars, while the blue bars represent the type and number of defects by engine.

Figure 4: Multi-Level Pareto Chart Example: Serial Number by Defect Code.


Using Factor Values in Pareto Charts

Values to the right of the blue and yellow bars represent the number of defects found times the factor value, representing the total amount of time required for rework. The resulting multi-level Pareto is re-ordered by the largest amount of rework time (long bars), to the smallest (short bars.).

Figure 6: Weighted Multi-Level Pareto Chart


ProFicient allows users to specify a factor value within Database Manager for each defect code. For example, a Timing Housing Leak might cost 2.10 hours of rework (see Figure 5). To use weighted values, bring up the Processing Options windowIn the "General Options" tab, click radial button, "Weighted (Count x Factor Value)" to create the Weighted Multi-Level Pareto chart found in Figure 6.
Figure 5: Factor Value for Weighted Pareto.

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