BS ISO 7870-3:2020 pdf free.Acceptance control charts.
This document gives guidance on the uses of acceptance control charts and establishes generalprocedures for determining sample sizes, action limits and decision criteria.An acceptance controlchart should be used only when:
a) the within subgroup variation is in-control and the variation is estimated efficiently,b) a high level of process capability has been achieved.
An acceptance control chart is typically used when the process variable under study is normallydistributed; however, it can be applied to a non-normal distribution.The examples provided in thisdocument illustrate a variety of circumstances in which this technique has advantages; these examplesprovide details of the determination of the sample size, the action limits and the decision criteria.
The following documents are referred to in the text in such a way that some or all of their contentconstitutes requirements of this document. For dated references,only the edition cited applies. Forundated references, the latest edition of the referenced document (including any amendments) applies.
For the purposes of this document, the terms and definitions given in IlSO 3534-1,ISO 3534-2 and thefollowing apply.
Iln the pursuit of an acceptable product or service, there often is room for some latitude in the abilityto centre a process around its target level. The contribution to overall variation of such locationfactors is additional to the inherent random variability of individual elements around a given processlevel. ln most cases, some shifts in process level must be expected and can be tolerated. These shiftsusually result from an assignable cause that cannot be eliminated because of engineering or economicconsiderations. They often enter the system at infrequent or irregular intervals, but can rarely betreated as random components of variance.
There are several seemingly different approaches to treating these location factors contributingvariation beyond that of inherent variability.At one extreme is the approach in which all variabilitythat results in deviations from the target value must be minimized.Supporters of such an approachseek to improve the capability to maintain a process within tighter tolerance limits so that there isgreater potential for process or product quality improvement.
At the other extreme is the approach that if a high level of process capability has been achieved, it isnot only uneconomic and wasteful of resources, but it can also be counterproductive to try to improvethe capability of the process.This often is the result of the introduction of pressures which encourage“tampering”with the process (over-control) by people qualified to work on control aspects but notproduct or process quality improvement programmes.BS ISO 7870 pdf download.