Misplaced Pages

Process capability: Difference between revisions

Article snapshot taken from Wikipedia with creative commons attribution-sharealike license. Give it a read and then ask your questions in the chat. We can research this topic together.
Browse history interactively← Previous editContent deleted Content addedVisualWikitext
Revision as of 08:08, 17 February 2008 editHanvanloon (talk | contribs)175 editsm Addition of ISO 15504 information and references← Previous edit Latest revision as of 23:41, 6 June 2024 edit undoSafariScribe (talk | contribs)Extended confirmed users, Page movers, IP block exemptions, New page reviewers, Pending changes reviewers, Rollbackers77,178 edits Changing short description from "Unique combination of tools, materials, methods, and people engaged in producing a measurable output" to "Workability and cooperation in producing a measurable output"Tag: Shortdesc helper 
(147 intermediate revisions by 80 users not shown)
Line 1: Line 1:
{{Short description|Workability and cooperation in producing a measurable output}}
A '''process''' is a unique combination of tools, materials, methods, and people engaged in producing a measurable output; for example a manufacturing line for machine parts. All processes have inherent ] which can be evaluated by statistical methods.
{{About|the quantifiable measure of a process|software process capability|Capability Maturity Model|and|ISO/IEC 15504}}


The '''Process Capability''' is a measureable property of a process to the specification. The output of this measurement is usually illustrated by a ] and calculations that predict how many parts will be produced out of specification. The '''process capability''' is a measurable property of a ] to the specification, expressed as a ] (e.g., C<SUB>pk</SUB> or C<SUB>pm</SUB>) or as a ] (e.g., P<SUB>pk</SUB> or P<SUB>pm</SUB>). The output of this measurement is often illustrated by a ] and calculations that predict how many parts will be produced out of specification (OOS).


Two parts of process capability are:
'''Process capability''' is also defined as the capability of a process to meet its purpose as managed by an organization's management and process definition structures ].
# Measure the variability of the output of a process, and
⚫ # Compare that variability with a proposed specification or product tolerance


== Capabilities ==
⚫ Two parts of process capability are: 1) Measure the variability of a process, and 2) Compare that variability with a proposed specification or product tolerance.
⚫ The input of a process usually has at least one or more measurable characteristics that are used to specify outputs. These can be analyzed statistically; where the output data shows a ] the process can be described by the process ] (average) and the ].


⚫ A process needs to be established with appropriate ]s in place. A ] analysis is used to determine whether the process is "in statistical control" If the process is not in statistical control then capability has no meaning. Therefore, the process capability involves only ] and not ].
===Measure the Process===


⚫ A batch of data needs to be obtained from the measured output of the process. The more data that is included the more precise the result, however an estimate can be achieved with as few as 17 data points. This should include the normal variety of production conditions, materials, and people in the process. With a manufactured product, it is common to include at least three different production runs, including start-ups.
⚫ The output of a process usually has at least one or more measurable characteristics that are used to specify outputs. These can be analyzed statistically, where the output data shows a ] the process can be described by the process mean (average) and the standard deviation.


⚫ The process mean (average) and standard deviation are calculated. With a normal distribution, the "tails" can extend well beyond plus and minus three standard deviations, but this interval should contain about 99.73% of production output. Therefore, for a normal distribution of data the process capability is often described as the relationship between six standard deviations and the required specification.
⚫ A process needs to be established with appropriate ]s in place. A ] analysis is used to determine whether the process is "in statistical control". If the process is not in statistical control then capability has no meaning. Therefore the process capability involves only ] and not ].


⚫ ==Capability study==
⚫ A batch of data needs to be obtained from the measured output of the process. The more data that is included the more precise the result, however an estimate can be achieved with as few as 17 data points. This should include the normal variety of production conditions, materials, and people in the process. With a manufactured product, it is common to include at least three different production runs, including start-ups.
⚫ The output of a process is expected to meet customer requirements, ]s, or ]s. Engineers can conduct a process capability study to determine the extent to which the process can meet these expectations.


⚫ The ability of a process to meet specifications can be expressed as a single number using a ] or it can be assessed using ]s. Either case requires running the process to obtain enough measurable output so that engineering is confident that the process is stable and so that the process mean and variability can be reliably estimated. ] defines techniques to properly differentiate between stable processes, processes that are drifting (experiencing a long-term change in the mean of the output), and processes that are growing more variable. ] are only meaningful for processes that are stable (in a state of ]).
⚫ The process mean (average) and standard deviation are calculated. With a normal distribution, the "tails" can extend well beyond plus and minus three standard deviations, but this interval should contain about 99.73% of production output. Therefore for a normal distribution of data the process capability is often described as the relationship between six standard deviations and the required specification.

⚫ ===Capability study===
⚫ The output of a process is expected to meet customer requirements, ]s, or product ]s. Engineering can conduct a process capability study to determine the extent to which the process can meet these expectations.

⚫ The ability of a process to meet specifications can be expressed as a single number using a ] or it can be assessed using ]s. Either case requires running the process to obtain enough measurable output so that engineering is confident that the process is stable and so that the process mean and variability can be reliably estimated. ] defines techniques to properly differentiate between stable processes, processes that are drifting (experiencing a long-term change in the mean of the output), and processes that are growing more variable. ] are only meaningful for processes that are stable (in a state of ]).

For Information Technology, ] specifies a process capability measurement framework for assessing process capability. This measurement framework consists of 6 levels of process capability from none (Capability Level 0) to optimizing processes (CL 5). The measurement framework has been generalized so that it can be applied to non IT processes. There are currently two process reference models covering software and systems. In the next 2-3 years, IT services and enterprise wide processes will be added. The ] in its latest version (CMMi continuous) also follows this approach. The referenced Process Assessment books describe this in greater detail.


== See also == == See also ==
*]
⚫ *]
⚫ *]
⚫ *]
*] *]
⚫ *] (CAPA)
*]
*] *]
⚫ *]
⚫ *] (CAPA)
⚫ *]
⚫ *]
*] *]

*]
⚫ ==References==
*]
⚫ * ], "Quality Engineering Handbook", 2003, {{ISBN|0-8247-4614-7}}
*]
⚫ * Bothe, D. R., "Measuring Process Capability", 2001, {{ISBN|0-07-006652-3}}
⚫ * Godfrey, A. B., "Juran's Quality Handbook", 1999, {{ISBN|007034003X}}
⚫ * ASTM E2281 Standard Practice for Process and Measurement Capability Indices


== External links == == External links ==
* * at ]/]
* * by ]
* - www.SiliconFarEast.com
* - download "Lean6" to analyze capability and track variability


{{Six Sigma Tools|state=collapsed}}
⚫ ==References==
{{Authority control}}
⚫ * Pyzdek, T, "Quality Engineering Handbook", 2003, ISBN 0824746147
⚫ * Bothe, D. R., "Measuring Process Capability", 2001, ISBN 0070066523
⚫ * Godfrey, A. B., "Juran's Quality Handbook", 1999, ISBN 007034003
⚫ * ASTM E2281 Standard Practice for Process and Measurement Capability Indices
* Process Assessment and ISO 15504 ISBN 13 9-780387-300481
* Process Assessment and Improvement ISBN 13 9-780387-300443


] ]
] ]
]
]
]

Latest revision as of 23:41, 6 June 2024

Workability and cooperation in producing a measurable output This article is about the quantifiable measure of a process. For software process capability, see Capability Maturity Model and ISO/IEC 15504.

The process capability is a measurable property of a process to the specification, expressed as a process capability index (e.g., Cpk or Cpm) or as a process performance index (e.g., Ppk or Ppm). The output of this measurement is often illustrated by a histogram and calculations that predict how many parts will be produced out of specification (OOS).

Two parts of process capability are:

  1. Measure the variability of the output of a process, and
  2. Compare that variability with a proposed specification or product tolerance

Capabilities

The input of a process usually has at least one or more measurable characteristics that are used to specify outputs. These can be analyzed statistically; where the output data shows a normal distribution the process can be described by the process mean (average) and the standard deviation.

A process needs to be established with appropriate process controls in place. A control chart analysis is used to determine whether the process is "in statistical control" If the process is not in statistical control then capability has no meaning. Therefore, the process capability involves only common cause variation and not special cause variation.

A batch of data needs to be obtained from the measured output of the process. The more data that is included the more precise the result, however an estimate can be achieved with as few as 17 data points. This should include the normal variety of production conditions, materials, and people in the process. With a manufactured product, it is common to include at least three different production runs, including start-ups.

The process mean (average) and standard deviation are calculated. With a normal distribution, the "tails" can extend well beyond plus and minus three standard deviations, but this interval should contain about 99.73% of production output. Therefore, for a normal distribution of data the process capability is often described as the relationship between six standard deviations and the required specification.

Capability study

The output of a process is expected to meet customer requirements, specifications, or engineering tolerances. Engineers can conduct a process capability study to determine the extent to which the process can meet these expectations.

The ability of a process to meet specifications can be expressed as a single number using a process capability index or it can be assessed using control charts. Either case requires running the process to obtain enough measurable output so that engineering is confident that the process is stable and so that the process mean and variability can be reliably estimated. Statistical process control defines techniques to properly differentiate between stable processes, processes that are drifting (experiencing a long-term change in the mean of the output), and processes that are growing more variable. Process capability indices are only meaningful for processes that are stable (in a state of statistical control).

See also

References

External links

Six Sigma tools
Define phase
Measure phase
Analyse phase
Improve phase
Control phase
DMAIC
Categories: