What is Statistical Process Control (SPC)
SPC is method of measuring and controlling quality by monitoring the manufacturing process. Quality data is collected in the form of product or process measurements or readings from various machines or instrumentation. The data is collected and used to evaluate, monitor and control a process. SPC is an effective method to drive continuous improvement. By monitoring and controlling a process, we can assure that it operates at its fullest potential. One of the most comprehensive and valuable resources of information regarding SPC is the manual published by the Automotive Industry Action Group (AIAG).
Why Use Statistical Process Control (SPC)
Manufacturing companies today are facing ever increasing competition. At the same time raw material costs continue to increase. These are factors that companies, for the most part, cannot control. Therefore companies must concentrate on what they can control: their processes. Companies must strive for continuous improvement in quality, efficiency and cost reduction. Many companies still rely only on inspection after production to detect quality issues. The SPC process is implemented to move a company from detection based to prevention based quality controls. By monitoring the performance of a process in real time the operator can detect trends or changes in the process before they result in non-conforming product and scrap.
How to Use Statistical Process Control (SPC)
Before implementing SPC or any new quality system, the manufacturing process should be evaluated to determine the main areas of waste. Some examples of manufacturing process waste are rework, scrap and excessive inspection time. It would be most beneficial to apply the SPC tools to these areas first. During SPC, not all dimensions are monitored due to the expense, time and production delays that would incur. Prior to SPC implementation the key or critical characteristics of the design or process should be identified by a Cross Functional Team (CFT) during a print review or Design Failure Mode and Effects Analysis (DFMEA) exercise. Data would then be collected and monitored on these key or critical characteristics.
Benefits Of SPC
- Improve Data Collection, Analysis, and Reporting
- Reduce Scrap, Waste, and Risk
- Optimize Manufacturing Operations
- Increase Savings and Customer Satisfaction
Get More from Statistical Process Control
When it comes to real-time Statistical Process Control (SPC), most solutions begin—and end—with control charts. Although control charts are excellent shop-floor tools, you’ll need other analysis tools to extract maximum information from your data.
7 Quality Tools
- Cause-and-effect diagram (also called Ishikawa diagram or fishbone diagram)
- Check sheet
- Control chart
- Pareto chart
- Scatter diagram
The 7 Supplemental (7-SUPP) Tools
- Data stratification
- Defect maps
- Events logs
- Process flowcharts
- Progress centers
- Sample size determination