What is Statistical Process Control...
Information & Training | SPC and Statistical Methods for Process Improvement.Statistical Process Control (SPC) has been in use since 1924 when a young engineer Walter Shewhart developed his first control chart at Bell Laboratories. SPC is the use of statistical techniques, e.g. collecting and analyzing data, so as to understand how a process is performing and using the knowledge gained to control the process to ensure the correct output is achieved.
The analysis of data gather from a process can provide a comprehensive insight into how the process actually operates. Is there variation in the outputs of the process? What is causing the variation? Is the level of variation acceptable? Are some process outputs un-acceptable due to the variation experienced within the process?
Statistical Process Control will create a focus and understanding on the reasons why the outputs of a process are changing over time. Analysis of the SPC data will identify the causes of process change and therefore solutions to address can be implemented.
The basis of Statistical Process Control is that there is an inherent level of variation in all processes. This variation may or may not be a problem. If the variation is at a level where there is no impact on the outputs of a process then the process is effectively stable and well in control. If however, the variation within the process results in un-acceptable outputs, then the process needs to be analyzed, the causes of variation identified and understood and the level of variation reduced, to that each and every the process output is acceptable.
There are three elements to SPC when applied to a process, namely:
Statistical investigation – Identifying a range of data to be recorded, structuring the data into a useful understandable format, analyzing the data to develop an understanding of how a process is operating, obtaining fact based conclusions using a scientific / mathematical approach to data analysis, making process changes based on the information and confirming the effectiveness of the changes in achieving desired process outputs.
Applying to a Process – the whole combination of manpower, machines, materials, methods, measurement and environment, working together to produce output.
Achieving the desired level of Control – making the process under investigation behave in a predictable consistent manner on an on-going basis.
Definition of Statistical Process Control.SPC is the use of statistical techniques to analyze a process, in order to develop an understanding of the level and reasons for variation within the process, with the objective of maintaining or reducing the process variation to within acceptable limits.
There are a wide range of statistical tools and techniques which can be applied to process improvement, such as Pareto charts, Histograms, Scatter diagrams, Run charts, etc.. The technique most synonymous with statistical process control is the SPC Control Chart or Shewhart Chart.
Information & Training.
SPC & Statistical Methods for Process Improvement.
- Process Capability. Variability Reduction. Statistical Process Control.
- Pre-Control. R&R Studies.
- Process capability indices Cp, Cpk, Cpm, Capability ratio.
- Performance indices Pp and Ppk.
- Variable Control Charts.
- Attribute Charts.
- Pareto Charts.
- Individual – X Charts.
- Histograms / Process Capability Analysis.
- Scatter Diagrams.
- Etc. … Etc. …
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