Statistical process control (SPC) is a method for ensuring that processes are predictable. It is a set of methods using simple statistical tools that are applicable by personnel at all levels to detect whether the process is under control.
Statistical Process Control charts enable your employees to distinguish signal from noise, so that they can work on the most critical issues to stabilize processes and improve overall process capability.
Scope And Deliverables
Prior to improving a process, it’s important to ensure that your current process is as good as it’ll ever be. That means you first need to make it completely predictable, by understanding all of the special causes of variation.
A statistical process control chart is a run chart of a sequence of quantitative data that enables you to separate signal from noise, so that you can respond to real problems. Common cause variation plots as an irregular pattern, mostly within the control limits. Any observations outside the limits, or patterns within, suggest (signal) a special-cause.
When a point falls outside of the limits established for a given control chart, those responsible for the underlying process are expected to determine whether a special cause has occurred. If one has, then that cause should be eliminated if possible.
Types of charts
There are many different types of control charts that can be used, each of which is appropriate for a specific situation or application. SatiStar’s consultants will help ensure that your people are using the correct type of chart for their process. Some common types of charts include:
- Individuals/ moving-range chart (ImR chart or XmR chart)
- XbarR chart (Shewhart chart)
- Averages as individuals chart
- Three-way chart
- EWMA chart (Exponentially-Weighted Moving Average chart)
- CUSUM chart (Cumulative Sum chart)
While these are the most common, there are many other types of control charts that may be applicable to your processes.
Common-cause variation is characterised by:
- Phenomena constantly active within the system;
- Variation predictable probabilistically;
- Irregular variation within an historical experience base; and
- Lack of significance in individual high or low values.
Common-cause variation is the noise within the system.
Special-cause variation is characterised by:
- New, unanticipated, emergent or previously neglected phenomena within the system;
- Variation inherently unpredictable, even probabilistically;
- Variation outside the historical experience base; and
- Evidence of some inherent change in the system or our knowledge of it.
Special-cause variation always arrives as a surprise. It is the signal within a system.
A Control Chart is primarily used to establish that a process is stable and predictable. The question answered by a Control chart is “has my process changed?”
The Process Capability Study answers the question, “is my process good enough to meet customer requirements?”
What We Will Do
The outcome for any SPC effort is to rapidly improve the output of processes. We’ll begin by spending time with your leadership team investigating and identifying potential opportunities for improvement to your processes – based on those issues that they care about most. We then collect actual process data, which is used during the subsequent SPC implementation work.
Employees are then given the mandate to identify and achieve statistically significant reductions in process variation, or step changes in process average performance. A critical requirement is that they must deliver this within a very short time period, usually a few days!
- Determine key process output measures for critical processes, beginning with those that affect your customers.
- Collect and analyze relevant process data.
- Determine which type of control chart is the most appropriate, and set up the charts.
- Train relevant employees in the use of their charts.
- Guide employees in how to interpret the data and use it to rapidly improve their processes by:
- Centering the process on target.
- Eliminating special causes variation.
- Understanding how to reduce common causes of variation.
- Moving the process to new and better levels of performance.
- Guide your leadership team on how to ensure that the rapid process improvements are achieved and sustained.
What We Need You To Do
- Commit to implementing an SPC program.
- Assign key personnel to become internal SPC experts.
- Enroll the relevant part of the entire organization in the effort.
- Provide access to relevant process areas.
- Ensure that requested data is provided in a timely manner.
- Set up and conduct periodic follow up to ensure appropriate leadership of the effort.
- Measure and track overall progress.
WHAT PEOPLE ARE SAYING
SatiStar's Experience Makes The Difference!