What is Statistical Process Control (SPC) Six Sigma?
Six Sigma is a set of tools used by businesses for quality control and process improvement. The Six Sigma method is often used to remove defects and optimize processes by monitoring operations and then analyzing the data and statistics collected.
Statistical Process Control (SPC) is a subset of Six Sigma and is used to monitor operations in order to identify any abnormalities and suggest possible solutions. As every manufacturing process will have some level of variation, SPC aims to provide a way to measure whether the variation is normal – and therefore not impacting efficiency – or abnormal and requires action in order to optimize the process.
Statistical process control methods plot process data over time to create a control chart that measures the degree of variation expected in any manufacturing process, called ‘common cause variation’. Any variations exceeding this norm are called ‘special cause variations’ and are flagged for attention. Improvements to the process can cause variation and create more predictability and output consistency. In addition, special causes can be examined and incorporated if they bring about improvement or eradicated if they harm output.
SPC Best Practices
It is not necessary to have a deep understanding of statistics in order to use statistical process control methods. All that is needed is the ability to interpret the meaning of the control chart and understand how to use that information to optimize processes. Following are best practices to ensure that SPC technology is used wisely:
Don’t measure too many variables – Including too many variables in your monitoring and control charts will be overwhelming and not productive. Instead, choose a few primary focus points.
Foster employee engagement- SPC is a tool to identify areas of improvement, but. forcing its use on employees will only lead to resistance. Make sure you educate the team about the importance of SPC and engage them in the process.
SPC is not a punishment – To receive honest information and charting, employees can not experience SPC as a punitive measure. Make sure they know that the intention is to optimize operations and not to punish them for any inefficiencies that are identified. Employees must see the benefits of using SPC and feel it is an asset, not a threat.
Pros and Cons of SPC
Pros
- SPC can help identify which variations are common cause and do not need special attention and enables you to prioritize optimizing the correct factors.
- Feedback is almost instantaneous as the control chart is plotted in real-time, and the variation will quickly be defined as common or special cause variation.
- This immediate actionable feedback eliminates the need for guesswork and random adjustments to achieve reduced process variations.
Cons
- It can be expensive to put SPC in place as, in most cases, a specialist would need to be brought in to train all personnel on the charting methods.
- Personnel cooperation is essential for SPC to work, and sometimes this can be a limitation as its use can be seen as an extra burden by employees.
- Although SPC can identify and flag special causes, it can not identify the source of the problem or a solution. Additionally, SPC can not decide which factors to chart. A human must still take this decision, leaving room for subjective error when choosing key factors to monitor.
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As an end-to-end solution, factories can use Matics to implement statistical process control methods. The solution can monitor systems and collect the data needed to create the control charts and then can provide the real-time information needed to make sure that the actions taken are working to optimize operations.
