Statistical process control (SPC) is a method of quality control which uses statistical methods. SPC is applied in order to monitor and control the manufacturing process. Monitoring and controlling the process ensures that it operates at its full potential. At its full potential, the process can make as much conforming product as possible with a minimum of waste. SPC can be applied to any manufacturing process where the "conforming product" output can be measured.
Execution
To create a SPC report we must have some Name Value data to analyze, access the desired data by opening the NV list and selecting the NV to for the SPC report. If the data is not suitable for a SPC report then the system will default to a Pareto Chart of the data.
In the Name Value window slect the SPC tab to choose your desired X-Axis Units. X-Axis Units can be selected from the following options:
- Number (Default)
- Date
- Unique Identifier (UID)
- Lot
- Unique Identifier + Lot
Click the Report Icon to produce the SPC report
SPC Report
The SPC Report analyzes the data using two charts, a Run and a Control Chart Analysis Summary.
Run Chart Analysis
A Run Chart is a line graph of data points plotted in chronological order that helps detect special causes of variation.
- To study observed data for trends or patterns over a specified period of time
- To focus attention on vital changes in the process
- To track useful information for predicting trends or patterns
- To understand variation within the process
- To compare a performance measure before and after implementation of a solution to measure the impact
- To detect trends, shifts, and cycles in the process
Control Chart Analysis
A Control chart plots time-ordered data, just as run charts do, however, the difference is that statistically determined control limits are drawn on the plot. Note that the centerline calculation uses the mean and not the median.
Why use a Control Chart:
- Statistical control limits establish the process capability
- Statistical control lines are another way to separate common cause and special cause variation; points outside the statistical limits signal a special cause
- Can be used for almost any type of data collected over time
- Provides a common language for discussing process performance
- Track performance over time
- Evaluate progress after process changes/improvements
- Focus attention on detecting and monitoring process variation over time
Run Chart Configuration
The Run Chart report can be configured in the SPC tab section to display or hide the following sections:
- SPC Run Chart - The entire Run Chart plot and all subsequent sections can either be displayed or hidden
- SPC Run Pass/Fail Section
- SPC Run Analysis Summary
- SPC Run List of All Flags
Control Chart Configuration
The Control Chart report can be configured in the SPC tab section to display or hide the following sections:
- SPC Control Chart- The entire Control Chart plot and all subsequent sections can either be displayed or hidden
- SPC Control Pass/Fail Section
- SPC Control Analysis Summary
- SPC Control List of All Flags (Nelson Rules)
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