SPC Definition: SPC stands for statistical process control. Statistical Process Control is a scientific visual method used to monitor, control and improve processes by eliminating special cause variation from manufacturing, service and financial processes. SPC is a key continuous improvement tool.
SPC is also a fundamental tool in six sigma methodology.
SPC Chart Described
The X bar is the top chart. The cross hairs represent the average over time. The most recent data is on the right hand side of the chart. There is a UC line and an LC line which stands for upper control limit and lower control limit. These limits are calculated based on the overall average of the chart and the average range. In the center of the X bar chart there is an mean line which is the average of all collected data.
The R chart is the bottom chart. The cross hairs represents the range of each data set. They correlate with the cross hairs on the top chart. There is an UC line (and sometimes a LC line) is dependent on the average range of the sample size.
The Y axis for the X bar chart is the average of the sample. The Y axis for the R chart is the number for the range of the sample.
Typically you sample 1 to 8 parts at a set frequency period. You then take the average of the sample size and plot it on the X bar chart. You plot the average in sequence, so the next point will be the furthest to the right. You then take the range of the sample size and plot that on the bottom R chart.
Discusses how to calculate the control limits
|SPC Training Video |
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Statistical Process Control (SPC) is a scientific visual method used to monitor, control and improve processes by eliminating special cause variation from manufacturing, service and financial processes. It is a key Six Sigma tool.
SPC directs the process champion when to make take action to adjust or investigate the process. Control chart SPC also prevents inappropriate or unnecessary process adjustments. SPC tells you when there is special cause variation or when the process is drifting. SPC can be used to catch machine wear, operator setup issues, raw material changes, and differences between similar machines. Overall, one uses SPC to prevent defects from occurring and tracks process improvement.
You will learn...
What is control chart SPC
Why use SPC
Process vs. product focus SPC
Types of SPC charts
Examples of control chart SPC uses
SPC and normal distribution
Making the SPC chart and the math behind SPC
Setting up the SPC charts
Interpreting the SPC charts
Special Cause Variation
SPC chart rules
Dynamic vs. Static Limits
Spec limits and process capability
Sampling frequency and sample size
Moving Range Chart and Calculations
For more details on the SPC course agenda, click here.
(Course created by Quality Assurance Solutions)
Control Limits and Specification Limits on a Control Chart
Discusses capability and control chart SPC with limits
Auditing SPC inspection
Learn how to audit a SPC inspection program.
SPC and Special Cause Variation
If you study SPC charts you see most of the data is close to the average with some of the data away from the average. The plotted points are random. Half of them are above the average and half of them are below the average. This is the expected look of a chart when the process is in control.
A SPC chart tells you when your process is out of control. Out of control means there is a special cause that was not there before. This could be an operator setup issue, wrong tooling, a change in raw materials or any unusual noise that can be investigated and eliminated.
By knowing the SPC definition and how to use the charts you improve your processes because it directs you to finding problems exactly when they occur. You can eliminate the noise before process significantly changes. This prevents defects from occurring and costing your company serious $$.
Walter Shewart invented the SPC definition in the 1930s. Before computers, people made SPC charts by hand. The charts were somewhat tedious but significantly helped companies. Due to computers, applying the SPC definition is now simple. Modern SPC Software creates the charts automatically, instantly imports data, and lets users to access charts from their desks.
Fortunately, I’ve used the best SPC Software in the USA and I used this software for 15 years. The software is the most popular real time enterprise SPC on the market.
- The software adds extensive value to improving your processes.
- The software centralizes the collected data all users have quick access to that data.
- With the software, you can automate data collection and input data from excel, minitab and databases.
- The software package works with any piece of measurement equipment that has digital output. This eliminates data entry errors and decrease data entry time.
- The software includes control charts, histograms and trend charts. You can review the charts one by one or compare several on the same page.
- The software makes advanced SPC charts such as moving average, moving range and cusum.
- The software lets users create custom reports.
- You can output an unlimited amount of statistics. Include these on your custom reports and charts.
- With the software you can create and save custom data filters and statistical filters. These filters let you examine data to fit your needs.
- You can save your favorite charts to desktops and easily review them as needed.
- You design how users enter data into the software. Users do not have to do any calculations. You can design the data entry module to conduct enhance calculations.
- The software stores and tracks all necessary traceabilities with each input. Quickly, you can conduct Anova studies with the tracabilities. This helps you eliminate special cause variation.
- With the software you can make and store multiple control charts with only one data entry session.
- The software monitors the data to quickly identify out of control processes. It can automatically send email to the processes champion. You define the SPC definition monitor rules for each characteristic.
- It allows you to set anchor points, make data notes, and use special characters for data markers.
- The software stores your specifications, allows dynamic and static control limits and provides statistical evaluations quickly.
- If data breaks any SPC definition rule, feedback can automatically be given to the operator for their action.
- You may publish real time data to the web for your customers or other facilities.
- The software provides dashboards for quick management review of the data.
|If you are interested in seeing a demo of this software for conducting real time SPC, histograms, pareto charts and capability studies please fill in the below form. |
The SPC Definition and SPC chart is a continous improvement tool and quite valuable to your quality assurance program.
Quality Assurance Solutions