ISO 22514 PDF
May 30, 2020 | by admin
The international standard ISO has been withdrawn and replaced by the standard ISO. In order to avoid confusion regarding. TECHNICAL ISO/TR REPORT First edition Statistical methods in process management — Capability and performance. Buy UNI ISO STATISTICAL METHODS IN PROCESS MANAGEMENT – CAPABILITY AND PERFORMANCE – PART 2: PROCESS CAPABILITY.
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Process capability statistics for characteristics following a multivariate normal distribution. In these circumstances, itwill only be possible to compute a Cpk or a Ppk index. They present a special appeal to those engaged in minimizing process variation around a targetvalue.
ISO 22514-2:2013: Statistical methods in process management – Capability and performance – Part 2:
If attributes data are generated by a measurement system that evaluates a variables measurement as a passor fail judgement, care must be taken to minimize any measurement system variation. Statistical methods in process management – Capability and performance – Part 6: More importantly the proportions out-of-specification items are: The method isfirst to identify the appropriate family of distributions, secondly to estimate the parameters of the distribution ofthe family that best explain the data by some efficient estimation method and finally to express the quantiles interms of the parameters of that distribution.
Each member body interested in a subject for which a technical committee has beenestablished has the right to be represented on that committee.
It has become necessary to draw a firmdistinction between these since it has been observed in industry that companies have been deceived abouttheir true capability position due to inappropriate indices being calculated and published.
Process capability estimates and performance measures1 ScopeThis part of ISO 25214 process capability and performance measures that are commonly used. Note that the probability paper method directly estimates fairly extreme quantiles and that this can beinaccurate. The data from each cavitymight form a single normal distribution. If the process ismonitored using a control chart, the control chart will show an in control state.
The following are theconditions that will apply for performance: The lower the index, the greater the proportion of items produced out-of-specification.
This enables isk direct comparison to be made between the dimensional performance of a characteristic and its specified requirements in terms of both location and dispersion.
There are two types of standard deviation to consider. NOTE 4 For a normal distribution 2. For a normal distribution, this processinterval is represented by six standard deviations. The single important differencebetween performance and capability is that for performance there is no requirement for the process to be in astate of statistical control nor for the process to be controlled using a control chart.
If the occurrence of nonconformities per hundred is so low that the NHU is very much less than the value 1,consider the number of nonconformities per million instead, i. The proportion nonconformingdepends upon the distribution and the value of the index.
This situation gives a one-sided specification. Sometimes, too, the estimator St 225114 preferredto Sw because it has more tractable statistical properties e. It is important for the user of this part of ISO to appreciate that variations exist that will be of a short-term nature as well as those that will be of iao long-term nature and that capability determinations using only theshort-term variation might be greatly different to those which have used the long-term variability.
EXAMPLE 2 A model for the diameter of bolts as in Example 1 could be the class of normal distributions without attempting to specify a particular distribution. An example of this is shown in Figure 2.
NOTE 3 For a non-normal distribution 2. Care should be taken not to interpretindices on the basis of cut-off points that have been derived for the normal distribution and hence are onlyapplicable for that distribution. However, if a target ornominal value is given for the product characteristic or process parameter the following measures might beappropriate.
Figure 1On occasions, process capability is taken to account for extra sources of variation such as a multiple streamprocess, for example, output from a multi-cavity injection moulding press.
ISO Pages 1 – 50 – Text Version | FlipHTML5
Continual improvement leads to reductions in the costs of failure and assists in the drive for survival 222514 anincreasingly more competitive world. If a characteristic, in statistical control and stable, has a CpkU of 0,86 and a CpkL of 0,91, the proportion ofout-of-specification can be determined using the method given above as follows.
NOTE 2 The function relates to a theoretical distribution. Issues such 2251 these and those given earlier will influence the referenceinterval and it is important that they are stated in any capability assessment.
Create your own isl. Hence Sw should be used with extreme caution. Various types of probability paper may be useful to identify the appropriate family of distributions.
Additionally, the rate of occurrence of nonconformities can be computed as the nonconformities per hundredunits NHU: 225114 is often calculated fromstatistics taken from a control chart and this is shown in A. This part of ISO does not attempt to explainwhat is meant by inherent variation, why it exists, where it comes from nor how it affects a process. The work of preparing International Standards is normally carried out through ISOtechnical committees.
NOTE 3 Care should be exercised in using this measure as it may contain a component of variability due to specialcauses the value of which is not predictable.