Z 1.4 Inspection Levels

Pharmaceutical sampling

Question

I am using a reduced switching rule and I don’t understand the meaning of the numbers in the first box. Total noncomforming less than limit number? What’s my limit number?Does production stability mean capability? Would I use 1.33?  The table has an arrow to reduced, so would I move to the next box?

Answer

The ANSI/ASQ Z1.4 standard has three inspection levels: normal, reduced and tightened inspection.  Initially you start at normal inspection, and can move to either tightened or reduced inspection depending on how lots are dispositioned.  Based on Figure 1 of the standard, the determination to move amongst the levels can be ascertained.  When you get to the reduced inspection level (Table II-C), you need to read the footnote (†).  It states “If the acceptance number has been exceeded, but the rejection number has not been reached, accept the lot, but reinstate normal inspection.”

A stable process or production is less about a capability index, and more about the control chart of the data showing a stable process.  In other words, the process is stable over time.

Steven Walfish

For more information about inspection, please view the resources found here.

Confidence Levels

 

Data review, data analysis, data migration

Question

I would like to confirm if ASQ Z1.4-2008 attribute tables are calculated based on 95% confidence level? I am using Table II-A, on page 11.

Answer

ANSI/ASQ Z1.4 tables are not technically calculated based on a 95% confidence level.  The technical definition of AQL is the quality level that is the worst tolerable process average when a continuing series of lots is submitted for acceptance sampling.  Some interpret it to mean if a lot has AQL percent defective or less, a lot would have a high probability of being accepted based on the sampling plan.  The standard does not specify the probability of acceptance explicitly.  The operating characteristic curve (OC Curve and the tables define the AQL as the percent defective that has a 95% probability of acceptance.  So though it is not a 95% confidence level, it is a 95% probability of acceptance.

Steven Walfish

For more information about AQL, please view the resources here.

Zero Acceptance Number Sampling Plans

Airplane, aerospace, AS9100

Question

Regarding Nicholas Squeglia’s Zero Acceptance Number Sampling Plans, in the 4th edition for lot size 151-280 (1% AQL), a sample size of 20 is provided.  However, in the 5th edition, for the same lot size 151-280 and AQL of 1%, the sample size is 29. Which is correct – a sample size of 20 or 29?

Answer

In the 5th edition of Nicolas Squeglia’s book, he mentions on page xii the rationale of the change in sample sizes.  From  the 5th edition, “in the early 2000’s, a large aerospace manufacturer was given permission by ASQ to reproduce the c=0 sampling table.  They modified the table by changing several sample sizes, and for convenience it was therefore originally decided to carry those modifications into the fifth edition.”

Table 1a is the original tables (4th edition and previous) which has the sample size of 29.  Use this table unless otherwise specified by contract.

Table 1b is the modified table which has a sample size of 20.

Thanks

Steven Walfish

Calibration Questions

Automotive inspection, TS 16949, IATF 16949

Question

I work at a hydraulic cylinder manufacturer. The company has homemade thread and ring gages in house that we are using for production that are not sent out for calibration but have a homemade master that is used to check them with once a year which does not get sent out either. I have been here 6 months and am thinking these gages and masters are a violation of ISO. Am I correct?

Answer

The short answer is yes. The intent of ISO 9001:2015’s subclause 7.1.5 is to ensure that your company determines and provides suitable resources to ensure valid and reliable monitoring and measuring results, when evaluating the conformity of your products; and 7.1.5.2’s that is to ensure that your company provides measurement traceability when it is a requirement or when your company determines it to be necessary to have confidence in the validity of the measurement results. It seems that your practice for controlling the homemade thread and ring gages cannot fully fulfill those purposes. This is how I would address the situation:

  1. Assign a unique identifier to each homemade thread and ring gage. Maybe you can do that through your Document Control process.
  2. Ensure that those gages are protected from deterioration or damage when they are not in use.
  3. Have the homemade master measured by a service able to provide you with reliable certified measurements. That will make that gauge traceable to national or international standards. It will also allow you to demonstrate that the piece is fit for its intended purpose.  That means, you will be able to use this piece as the standard during the in-house calibration of the rest of the gages.
  4. Conduct an “in-house calibration” of each gage you use in production. You will need to issue an in-house calibration certificate for each one of those pieces, indicating on those documents how you achieve traceability to NIST or equivalent. If possible, identify the error for each one of those individual measurements you perform during calibration. Do not forget to include a statement indicating that the gauge was found suitable/unsuitable for use. That will demonstrate that each gage is fit for its intended purpose.
  5. Include ALL the gages in your calibration program. Make them subject to all the applicable provisions of your Quality System.

This approach will allow you to demonstrate that your thread and ring gages are properly controlled and maintained. If controlling those gages has not been an issue in the past, there is no guarantee that the situation will remain the same in the future. That is managing risk 😉

Aura Stewart

For more information about calibration, please see the resources here.

Aerospace Surveillance Audits

Airplane, aerospace, AS9100

Question

In reference to AS9104/1 clause 8.2.2.f “Auditing of the entire AQMS standard on all shifts is required for initial and recertification audits. For surveillance audits, the planning shall include coverage of multiple shifts, when the audit plan activities occur across multiple shifts.”

The identified process is “Production” but shift one conducts assembly and shift two kits parts for assembly. Since “Production” spans both shifts but “activities” are distinct on each shift, do you have to audit both shifts during every surveillance audit?
Answer

It would be required that Production be audited on both shifts when it is planned for surveillance audits.  For example, if the acquire business, design & development, and procure parts/materials were audited in Annual Surveillance #1 and production and procure parts/materials were audited in Surveillance #2, then second shift would only require to be audited during Surveillance #2.

Buddy Cressionnie

Learn more about the AS9100 standards here.

Sampling Foils, Films, and Labels

Manufacturing, inspection, exclusions

Question

My question is about sampling aluminium foils, films used in packaging and sticker labels received in rolls which are wound around a core. I can decide to chose the number of rolls to sample from using the tables given in Z1.4, but how should I decide on the amount of stickers and aluminium foil and film to be sampled? I ask this question since it is practically impossible to sample from within a wound roll.
Answer

The ANSI Z1.4 and Z1.9 standards might be applicable when all units do not have the same probability of being selected.  Since you cannot sample units closer to the core, and defects would never be detected unless they occur at the end of the roll, I would recommend a different strategy, either using a vision system (100% inspection) or in process inspection.

If you want to use the standard, the sample size should be based on the number of samples, not the number of rolls.  For example, a roll with 5000 labels would be an N=5000 not N=1.

Steven Walfish

Learn more about visual inspection here.

ANSI Z1.4 Reduced Inspection

Question

If you have Ac=0 and Re=2 what do you do for 1? I have not used the reduced sampling before, so am curious what should be done in this instance.

Answer

If you review the footnotes for Table II-C of ANSI Z1.4, you will see that there is a note (†) that states: If the acceptance number has been exceeded , but the rejection number has not been reached, accept the lot, but reinstate normal inspection (see 10.1.4).  So in your case, with a single reject, you would accept and reinstate normal inspection.

Steven Walfish

ISO Requirements or Good Documentation Practices?

 

Calibration

Question

Are these standard for ISO or just good documentation practices?

1. All entries, except IPQA, should be made with blue ball pen in clear and legible handwriting.
2. IPQA entries shall be done in black ball pen.
Answer

I can sense what it is happening at the place where this question originated. In the past, I saw a company where the person in charge of the Quality System was saying “this is a ISO requirement” to enforce what in this person’s opinion was a best practice. Nobody questioned those statements because “it is an ISO requirement”. So, the answer to the question is, those are best practices, not ISO requirements. Please see below the ISO 9001:2015’s clause pertaining to this question.

7.5.3 Control of documented information

7.5.3.1 Documented information required by the quality management system and by this International Standard shall be controlled to ensure:

  1. a)       it is available and suitable for use, where and when it is needed;
  2. b)       it is adequately protected (e.g. from loss of confidentiality, improper use, or loss of integrity).

7.5.3.2 For the control of documented information, the organization shall address the following activities, as applicable:

  1. a)       distribution, access, retrieval and use;
  2. b)       storage and preservation, including preservation of legibility;
  3. c)       control of changes (e.g. version control);
  4. d)       retention and disposition.

Documented information of external origin determined by the organization to be necessary for the planning and operation of the quality management system shall be identified as appropriate, and be controlled.

Documented information retained as evidence of conformity shall be protected from unintended alterations.

NOTE  Access can imply a decision regarding the permission to view the documented information only, or the permission and authority to view and change the documented information.

As you can see, no reference to any ink color whatsoever. Legal documentation tends to be completed by using blue ink to differentiate originals from Xerox copies. However, today’s technology allows us to have color copies.

Regards,

Aura Stewart

ISO 9001: 2015 Clause 8.4.3

Mr. Pareto Head and Supply Chain comic strip

Question

It’s not clear to me who an external provider may be. Could it be an electrical contractor, a lunch truck, a caterer, or other similar? That thinking is tremendously different than just the traditional “supplier” which is what this company has using been for many years. So there’s that concern. Also, advising our external providers what equipment to use, how to use it and how to train their people? Is that really what’s said here? That would require tremendous knowledge in our organization that most likely is not here. What exactly is being said here? I’m a little confused how to address this requirement. Finally, section (e): we must communicate to the external provider how we are going to measure them? Can it be done through email, or phone, or what is a common method for meeting the requirement? Thanks much.

Answer

Who is an external provider?

ISO 9001:2015, 8.4.1 states, the organization shall determine the controls to be applied to externally provided processes, products and services when:

  1. products and services from external providers are intended for incorporation into the organization’s own products and services;
  2. products and services are provided directly to the customer(s) by external providers on behalf of the organization;
  3. a process, or part of a process, is provided by an external provider as a result of a decision by the organization.
    1. Refers to a product that becomes part of your product; for example, a bolt incorporated into a seat assembly. You purchase these.
    2. Refers to a product that is “dropped shipped” to a customer. Think of an Amazon purchase where the product comes from a second party under the Amazon logo.
    3. Refers to a process that is outsourced as a result of the organization’s decision to have the process managed externally. For example, the heat treating of a part where the part needs to be heat treated but the organization does not have that process internally.

Therefore, an electrical contractor, a lunch truck, etc. are not included since they are outside the scope of the QMS.

Secondly, “advising our external providers,” refers to the type and extent of control.  Will you perform 100% incoming verification, or require material certifications, or require certification to a quality management standard? In certain instances, you may want to specify the equipment or training an external provider must implement.  For example, for outsourced welding, your requirement might be that welders are certified by the American Welding Society or your calibration company be accredited to ISO 17025.

How will you measure an external provider?  It can be on-time delivery, responsiveness to requests, PPM targets.  Communicating the measurement (8.4.3 e) is related to 8.4.1, “retain documented information of these activities and any necessary actions arising from the evaluations”.  Therefore, a record must be retained.

George Hummel