Recently, there is a debate in my organization about Defective Parts Per Million (DPPM) computation.
Camp 1 – DPPM = (No of parts rejected / No of parts inspected) * 1,000,000
Camp 2 – DPPM = (No of parts rejected / No of parts received) * 1,000,000
We perform sampling inspection based on AQL.
Camp 1 insists they are correct and likewise for Camp 2. Which is correct or more appropriate to reflect supplier quality?
This is not an uncommon question. If you look at the standard, they define the % nonconforming as the number of parts nonconforming/number of parts inspected x 100. If you are looking at DPPM, instead of multiplying by 100, you put in 1,000,000. This means that by your definition, Camp 1 is correct. This is also what was intended by the creators of the sampling scheme.
Sr Performance Improvement Specialist
ASQ Fellow, CQE, CQA, CMQ/OE, CSSBB, CSSMBB
Fort Worth, TX
My customer wants to get ISO 9001:2015 certified. He refuses to create a first-article, in-process, and final-inspection report. He has a router sheet that has a tiny space for final inspection brief information and the operator’s initials; no inspection data is available.
In his quality manual and processes he addresses “Time Studies” and “Statistical Process Control” but he refuses to record his inspection data because this “complicates and delays” his production. I told him this is a weakness in his QMS but he says it’s not. Will this issue jeopardize his ISO certification?
I would ask how the organization could present objective evidence with the requirements of Clause 8.5.1 including – ‘shall implement production and service provision under controlled conditions.’
Do EHS procedure have to be managed under ISO 9001:2008 if the company is not ISO 14001 certified?
It depends – are the EHS procedures part of the QMS of the organization. If so, yes. Otherwise no.
Recently one of our business units had an ISO 9001: 2008 audit and during the audit they received a couple NCRs on welding as a special process.
One of the NCRs was “Some welders are not qualified prior to welding on product.”
As a matter of fact, our company has developed its own qualification program based on the our needs consisting of the following steps:
– The minimum requirement of least 2 years or more experience as a welder before starting the job.
– In class training for weld specifications, blue print reading, equipment, weld supplies, visual acceptance/ rejection criteria and equipotent TPM program conducted by our QE.
– Hands on exam – the result of this test is reviewed by a QE and weld supervisor without performing any bend test, pull test or other types of DT.
– Annual recert. program based on a written exam and weld coupons visual inspection results.
The CB auditor is asking us to send the coupons out to a certified lab for bend testing or having all the welders certified by AWS. Is that required per ISO 9001? As a side note, every time we design and develop a new model we conduct all types of crash tests, FEA and durability testing in design validation phase.
From George Hummel:
I would not accept the auditor’s comments. He/she is consulting.
From Charles Cianfrani:
No. It appears that the CB auditor is adding requirements. The organization has a process, and if it is effectively implemented that should be satisfactory evidence of conformity.
Regarding ISO 9001: 2008 (or 2015) auditing, I have always been trained that a work instruction when implemented as supporting the QMS can be audited as it is supporting the effectiveness of the QMS. I was recently told by a business owner that not only is that not true, he does not have to show me his work instruction. I would like to reply with a clear technical response. Can anyone share their view on this?
Thank you for your question. Of course you know you’re right. It sounds like you have a major nonconformance against Clause 5.1 on your hands.
A Fellow of the American Society for Quality
Devos Associates Inc.
ISO 9001:2015 clause 7.5.1b states the following :
The organization’s quality management system shall include: documented information determined by the organization as being necessary for the effectiveness of the quality management system/
Documented information includes both procedures and records see appendix A.3 (Documented information).
Since the work instructions are supporting the QMS, it is part part of the QMS, and can be audited as part of both the internal audit and external audit. It appears that part of the confusion may be caused by a lack of understanding of the new term “documented information.”
John G. Surak, PhD
– Providing food safety and quality solutions –
A member of Stratecon International Consultants
There has been some debate over using the MIL-STD-1916 acceptance sampling plan over the ANSI/ASQ Z1.4-2003 (R2013) sampling plans. The opinion is that the ANSI/ASQ Z1.4-2003 (R2013) is outdated and no longer an acceptable method of determining a qualification sample plan and the MIL-STD-1916 should be used in place of ANSI/ASQ Z1.4-2003 (R2013). Do you have information around this debate over which sampling plans are acceptable by the FDA?
FDA does not (and can not) tell you what sampling plan is to be used. The FDA requirement is that the plan be statistically valid. As long as you follow the regulation, you are meeting FDA requirements.
In medical device manufacturing the key point is to have the plan accept on zero defectives. This point is not FDA but legalese. It is based on past lawsuits. The plan “Zero Acceptance Number Sampling Plans” by Nicholas L. Squeglia (available from ASQ) has been widely adopted for this reason.
ANSI/ASQ Z1.4 in not outdated and continues to be widely used. It is the American National Standard Institute (ANSI) version of MIL-STD-105 which the government discontinued maintaining, allowing ANSI to maintain it along with many, many other MIL-STD’s as a government cost reduction.
MIL-STD-1916 can be used but it is not widely used because of its difficulty and practical use.
I am confused about the values used for AQLs. For example in Table II-A the AQL values range from 0.010 to 1000. Where do these values come from and what do they mean?
The table states, “AQLs, in Percent Nonconforming Items and Nonconformities per 100 Items .” At first I thought the values were percentages, but how can you have more than 100, as in 100%, as the values go up to 1000? Also how can there be more than 100 nonconformities per 100 items, unless one part can have multiple nonconformities?
Just looking for clarification on the AQL numbers, what they mean, and how to interpret them.
Let’s start with the definition of Acceptable Quality Level (AQL). From Z1.4, the AQL is the quality level that is the worst tolerable process average when a continuing series of lots is submitted for acceptance sampling. Although individual lots with quality as bad as the AQL can be accepted with fairly high probability, the designation of an AQL does not suggest that this is necessarily a desirable quality level. The AQL is a parameter of the sampling scheme and should not be confused with a process average which describes the operating level of a manufacturing process. It is expected that the product quality level will be less than the AQL to avoid excessive non-accepted lots.
The columns with percentages greater than 100% should not be included in the standard, but remain as indication of how to interpret lots where the entire sample is defective. It has some statistical relevance with use of the switching rules, but for the general practitioner, it should be ignored.
Hope this helps.
My question concerns the process performance metric DPMO (defects per million opportunities). I want to use this to quantify a particular supplier’s performance. My question is, is the number of defects referred to in the calculation the number of defects produced by the supplier (in which case it would involve data I don’t have access to), or is it the number of defects experienced by the customer (which is us)? I of course can count the number of defects we receive from the supplier, but if this metric is supposed to be based on the number of defects produced by an organization, I would have no way of knowing how many defects are produced by the supplier’s process, but contained within the supplier’s facility. My hope is to be able to characterize the supplier’s process performance in terms of sigma level.
The DPMO metric is not usually considered a point estimate of the true percent defective in the lot (either at the supplier or customer site). It is a relative performance metric used to equate the observed percent defective from a sample to defective units per million opportunities. If a supplier culls out all the defective units before shipping to you (i.e. perfect inspection system), your internal DPMO would be 0, even if the supplier DPMO is high. If your goal is to characterize the supplier’s process performance in terms of sigma level, you would need their data, as the data you collect internally is just an estimate for the average outgoing quality from the supplier and not their process performance.
Is there any criteria available for the frequency of document revision in ISO 9001 or ISO 13485? Some organization don’t revise the documents for a period of more than 2-3 years. The reason provided by the organization is that there were no changes during this period. Do ISO standards mandate the revision of documents within a certain time frame? Can we treat this as non-compliance, if the documents are not revised over a period of 2-3 years ?
There are no criteria nor a requirement for document revision in ISO 9001:2015, 7.5.
ISO 13485:2016, 4.2.4, states, “review, update as necessary and re-approve documents.” This leave the review to the discretion of the organization.
Thus, there is no mandatory review frequency and no non-conformance if documents are not revised within a determined time frame. ISO 13485 does require a review, however. But, the frequency of the review is not mandated.
There is a second part to 7.6 para “a” which reads; “where no such standards exist, the basis used for calibration or verification shall be recorded.” It is clear for shops that are complying to the ISO 9001:2008(E) we need to have measurement standards traceable to international or national measurement standards. My question has to do with cylindrical plug gages that are used at the machines to verify manufactured print dimensions. The pins/plug gages are not sent out at intervals for calibration however, they are compared to a traceable measurement standard before being issued to the manufacturing area. We consider these gages to be calibrated “as used ” and we do not record the intial actual size of the pins/plug gage but issue it only on the basis that the size was verified against a traceable measurement standard. Are we required per Para 7.6 to record the actual size of the pins/plug gages?
Thank you for your question. What you are describing is verifying prior to use, rather than calibration. If the rings or other standards being used to check these plug gauges each day are properly calibrated and traceable to national standards, you are compliant with ISO 9001:2015. If you are registered to AS 9100 or TS 16949, stricter requirements will apply and you may not be meeting those requirements for recording variable results of calibration.
Denis Devos, P.Eng
A Fellow of the American Society for Quality
Devos Associates Inc.