AS9100 7.1.5.2 Measurement Traceability

Airplane, aerospace, AS9100

Question

Can a manufacturer use “reference only” M&M equipment to accomplish in-process checks as long as these items are verified later on by “Inspection” using calibrated and/or verified equipment?

Would all of the measurements have to be verified by properly calibrated equipment?

Answer

The practice of using “reference-only” devices for in-process measures is not noncompliant with the standard.  The formal inspections to accept product would require use of calibrated equipment.

In clause 7.1.5.1, the standard clearly states “the organization shall determine and provide the resources needed to ensure valid and reliable results when monitoring or measuring is used to verify the conformity of products and services to requirements.”  And in clause 7.1.5.2, “hen measurement traceability is a requirement, or is considered by the organization to be an essential part of providing confidence in the validity of measurement results…”

Users and auditors should look at formal inspections steps and final buy-off to determine if any nonconformities were escapes from in-process measurements being conducted without calibrated devices.  Customer complaints can also be analyzed to see if any escapes were a result of failed in-process inspections.  If so, then the organization did not properly determine and provide the appropriate resources.

Buddy Cressionnie

Buddy has written extensively about this standard. ASQ members have access to his articles here.

Z1.4 Inspection Requirements

Automotive inspection, TS 16949, IATF 16949

Question

Our customers require that we follow the ANSI Z1.4 standard for attribute sampling plans; however, it is not feasible to wait until lots are completed to perform inspections. Lots can be large and run for many days and waiting until lot completion to determine the sample size, based on the finished lot size, is too late because we will have missed our chance to correct any production issues that may result in defective parts. Another limitation is a lack of space to stage product while waiting for the final inspection of the completed production lots. Product is made as orders are received, and not typically stored as inventory, so our on-time delivery demands also hinder our ability to hold product for final inspections of completed production lots. Therefore, we are seeking guidance on a practical way to implement a in-process inspection during production that follows the ANSI Z1.4 standard.

Answer

Yes, you can sample as you produce to get to the sample size.  It is important that you keep track of your accept/reject items.  Since you know how long you are running the product, you can project the approximate lot size to get the sample size.  Work with your scheduler before the product starts so you can take samples early and continue on in the process.

In addition, if you have material changes as the product is running, I am sure that you are sampling then to make sure everything is set correctly, you can use those samples also.  As an example, let’s say your product is running 4 days and based on the projected lot size, you have a sample of 28 to take, you could take 7 samples each day spaced throughout the day or you take 10 samples the first day, 7 the second day, 6 the third day and 5 the last day of production.  You need to figure the right sequence that fits your history of the product.

Jim Bossert

Purchase a copy of Z1.4 here.

AQL Calculation Explanation

Reporting, best practices, non-compliance reporting

Question

Regarding part of your answer to a post found here, you state:

“The calculation of AQL is not dependent on lot size. In other words, a sample size of 315 gives a minimum AQL of 0.04, so a larger sample is required to estimate an AQL of 0.01.”

Can you explain for the non-statistical folks like me people how that math works? Specifically, I am wondering what the minimum sample size would be for an AQL of 0.25, when using Special Inspection level S2? Would it be a minimum of 50, no mater what the lot size is?

Answer

Acceptance sampling procedures were developed during the early 1920s at Western Electric Company and later formalized at Bell Telephone Laboratories where terms like producer’s risk and consumer’s risk were established.  Later, during World War II, sampling plans such as MIL-STD-105 were developed by Harold F. Dodge and others working with the Army Quartermaster Corps (Dodge, 1967).

Two special features were employed in order to gain agreement with the large body of military suppliers.  One was the use of the AQL as opposed to the RQL in presenting the plans.  The goal at the time was to focus on rewarding suppliers for production whose quality levels were considered good.  RQLs were recognized but not often brought to the surface during discussions. Also, at that time, the term “AQL” was deliberately vague or inexact.  It was a close approximation, not an exact probability statement.

The other feature was the practice of increasing sample sizes with increased lot sizes.  As noted in Section 3, in most situations, the lot size does not factor in plan construction (based on the binomial).  For many, however, this lacks intuitive appeal.  Therefore, in the development of MIL-STD-105 and its derivatives a deliberate increase in sample sizes for higher lot sizes was introduced, with corresponding increases in acceptance numbers for similar AQLs.  Clearly, this practice resulted in over-sampling and consequent increased inspection costs.  Government operatives believed that the increased sampling cost was of small consequence relative to the power to persuade.

For the binomial distribution you solve for the AQL that gives a high probability of passing.  Usually this probability is set at 95%.  For example if you have a sample size of 80 units with an accept/reject of 1, an AQL of 0.65% would have a 90% probability of passing the sampling plan.

You can use Excel to solve this with the function

=BINOMDIST(1,80,0.0065,1)

Hope this helps,

Steven Walfish

Click here for more about these standards.

Sampling Plan Review?

Chart, graph, sampling, plan, calculation, z1.4

Question

When following ANSI/ASQ Z1.4-2003 (R2018), if a product has been placed in a “reduced” sampling plan based on the previous 10 lots results, is it a requirement to convert back to a “normal” sampling plan on an annual basis, or should that decision remain based on supplier performance? I have been told that we should revert to normal sampling each year, but I do not see that in the AQL inspection manual.

Answer

The standard does not require annual (or periodic) review of the sampling plan.  The switching rules are time invariant, and reflects just the normal flow of lots, which can span more than a year.  Unless the supplier requires a change in the inspection level, the standard is silent on resetting to the normal level annually.

Steven Walfish

Click here for more on these standards.

7.1.5.2 AS9100 D

Airplane, aerospace, AS9100

Question

Section 7.1.5.2 of AS9100D States that “the organization shall establish, implement, and maintain a process for the recall of monitoring and measuring equipment requiring calibration or verification.”

Are calibration and verification both referring to the checking of equipment to make sure that it is suitable for it’s purpose, or is verification referring to the measurements taken on product? More specifically, does this require the organization to be able to identify which piece of measurement equipment made which measurements? In other words, if I have two micrometers that are both in a system that recalls them periodically for calibration, have I satisfied the requirements of 7.1.5.2 even if I don’t record which micrometer makes which measurements during it’s daily use?

Answer

The calibration or verification both refer to the monitoring and measurement equipment.  The AS9100D additional text is consistent with the ISO 9001:2015 by referring to calibration or verification.  The monitoring and measurement equipment could require verification as meeting requirements instead of a calibration.  If monitoring and measurement equipment is found to be out-of-tolerance and there is a product conformity impact, then it is very helpful if the organization has identified which instrument was used for which job.  Otherwise, the recall of product or alerting customers is much broader since the impact is not understood.  There is not specifically an AS9100D requirement to record which monitoring and measuring equipment was used but it is a good practice.

Buddy Cressionnie

ASQ Members: read the latest about AS9100D here.

Z 1.4 AQL Levels

Food safety testing, lab, standards

Question

I need help understanding the AQL values in the tables of ASQ Z1.4. They are defined in paragraph 4.5 as percentages or ratios, but there are some values that are less than 1 and greater than 100. How should these values be interpreted?  Since this standard is for attribute data, is there a standard for variable data?

Answer

A percentage can be from 0 to more than 100% depending on what the ratio represents.  First we need to define AQL.  Section 4.2 states “The AQL is the quality level that is the worst tolerable process average when a continuing series of lots is submitted for acceptance sampling.”  Therefore, an AQL of 0.65% means that on average we can accept 65 defects per 10,000 units in a lot.  The sampling plans with percentages greater than 100% are carried over from the MIL-STD-105 and are considered to be antiquated and not used any longer.

The ANSI standard for variable data sampling plans is ANSI/ASQ Z1.9.  It is based on probability of being outside the acceptance region.

Steven Walfish

Looking for the latest copy of the Z standards?  They are available here.

AS9100 D and ISO 9001: 2015

Airplane, aerospace, AS9100

Question

Is there a document that compares the requirements of AS9100 D against the requirements of ISO 9001:2015?

I am looking to update our system to AS9100 D, and have the standard, however it would be helpful to have a document to help identify the gap between the two.

Answer

ISO 9001:2015 is embedded in AS9100D as the baseline.  If you look at AS9100D text…the regular text is ISO 9001:2015 text and the bold-italics text are the additional Aviation, Space & Defense text.  So what you are looking for regarding the additional requirements is the bold-italics text.

I hope this is helpful.

Buddy Cressionnie
9100 Americas Leader

Escalation Process and ISO 9001: 2015

Chart, graph, sampling, plan, calculation, z1.4

Question

I have created a project and problem escalation pyramid to help associates understand when and who is involved when a project or process issue needs escalation. I would like to know what clause in ISO:9001-2015 this would fall into?

Answer

Thank you for your question.

It sounds like you have created an escalation process for when outcomes don’t meet requirements.  In this case it sounds like ISO 9001 Clause 8.7 “Control of Nonconforming Outputs” would apply.   If the escalation process is specific to something like an engineering design process, then Clause 8.3.2 “Design and Development Planning” and/or Clause 8.3.4 “Design and Development Controls” could apply.

Also, in a general sense, if a process issue needs escalation, it’s part of the plan-do-check-act cycle described under Clause 4.4 “Quality Management System and its Processes”.

I hope you were able to find these references useful.

Denis Devos

A Fellow of the American Society for Quality
Devos Associates Inc.
(519) 476-8951
www.DevosAssociates.com

ISO 9001: 2015 and “Effectiveness”

Control chart, data, analysis

Question

ISO 9001:2015 references measurement of “effectiveness” throughout the standard. My question is what methods/techniques are typically used to measure “effectiveness”? Is it purely a quantitative analysis of metrics, or does it also involve subjective evaluation that may not be driven by statistics or metrics? Also, is it expected that effectiveness be measured for each process/procedure?

Answer

Thank you for your question.

Let’s begin with the definition of effectiveness from ISO 9000:2015.

Effectiveness is “the extent to which planned activities are realized and planned results are achieved.”  This definition requires that you know what the expected outcome (or objective/target) you want for a given task, project or process.  The first step is to know what you want to achieve, and then ask yourself what would be the best means to determine the extent to which that objective was met?

Yes, it is expected that effectiveness be (suitably) measured for each process. This is at the heart of the Plan-Do-Check-Act cycle.  Also, please read ISO 9001 Clause 4.1 and Clause 0.3.

As far as quantitative vs. qualitative metrics are concerned, you will have to decide what best measures the outcome of the process.  Also consider the cost of data collection.  Often, easy-to-collect qualitative data can suffice.   And don’t be deterred if quantitative data cannot be obtained.  As Dr. Deming so wisely stated: “Sometimes we have to settle for inexact measures of exactly the right things”.

Denis Devos

A Fellow of the American Society for Quality
Devos Associates Inc.
(519) 476-8951
www.DevosAssociates.com

ISO 9001: 2015 and Vendor Certification

Suppliers, supplier management

Question

We are ISO 9001:2015 certified and have a sole source vendor who is considering dropping their ISO certification. What is the best course of action to retain this vendor if they drop their ISO?

Answer

Thank you for your question.

Unless you are in an industry where you are required to have your suppliers registered to ISO 9001, (for example, the automotive industry under IATF 16949), or you have specific customer contracts which require this,  the choice is entirely yours whether or not your suppliers are registered to ISO 9001.

If your company wants to press the issue and require ISO 9001 as a condition for this supplier to continue to do business with you, be prepared for them to give you up as a customer.   If however, this is a valued supplier with a history of strong performance, you don’t want to dismiss a valued supplier partner.   If you decide to keep them, simply change your purchasing procedure to allow yourself the latitude for management to approve and use suppliers without ISO 9001 certification.

Denis Devos

A Fellow of the American Society for Quality
Devos Associates Inc.
(519) 476-8951
www.DevosAssociates.com