Z1.4 2008: AQL, Nonconformities, and Defects Explained

Pharmaceutical sampling

Q: My question is regarding the noncomformities per hundred units and percent nonconforming.  This topic is discussed in ANSI/ASQ Z1.4-2008 Sampling Procedures and Tables for Inspection by Attributes under sections 3.2 and 3.3 on page 2.  Regardless of the explanations provided, I find myself puzzled as to what the following numbers refer to in “Table II-A– Single sampling plans for normal inspection (Master table).”

Specifically, I am having problems understanding the following unit numbers just above the Acceptance and Rejection numbers (example, 0.010, 0.015, 0.025, 1000).  Do these represent percent noncomformities and if so,  does 0.010 = 0.01%, and conversely, how can 1000 = 1000%?

As you may see, I am very confused by these numbers, and I was hoping to have some light shed on this subject. Thank you for your answers in advance.

A: The numbers on the top of the table are just as the questioner stated: .0.010 = .01% defective.  That is the acceptable quality limit (AQL) number.  Generally, most companies want 1% or less, but as noted in the table, it does go up to 1000. It is extreme to think of something being more than 100%, but consider that it may be a minor or cosmetic defect that does not affect the function but just does not look good.  Scratch and dent sales are a common result of these higher numbers.

The AQL number is the worst quality level you would expect to find at this level.  The thing you have to remember is that these plans work best when the quality is very good or very bad.  If you are at the limit, you could end up taking more samples and spend a lot of time in tightened inspection.

Many people use percent nonconforming instead of percent defective, simply because of the connotation of “defective.” No one wants to say they shipped a defective product.  They may have shipped a nonconforming product that the customer could not use simply because their requirements were too strict, where another customer may be able to use the same thing because they have less stringent requirements.

Jim Bossert
SVP Process Design Manger, Process Optimization
Bank of America
ASQ Fellow, CQE, CQA, CMQ/OE, CSSBB, CMBB
Fort Worth, TX

For more on this topic, please visit ASQ’s website.

Does ISO 9001 Clause 7 Apply to Processes?

Manufacturing, inspection, exclusions

Q: Does clause 7 Product Realization in ISO 9001:2008 Quality management systems–Requirements apply to the design and development of manufacturing processes?

We have four facilities that are ISO 9001 certified under one certificate. One location designs the product, and the other facilities manufacture it. In the “design facility” we follow the requirements of clause 7. In the manufacturing facilities, we currently do not apply clause 7 for the process of developing the manufacturing processes.

A: ISO 9001 clause 7.3 is applicable to the design and development characteristics of a product.

ISO 9001:2008 clause 7.1 (Planning of Product Realization) and its reference to clause 4.1 (General Requirements) is more specific to product planning to ensure that the product quality objectives and the processes/resources are available to produce a product that will meet defined quality requirements as specified during design and development in clause 7.3.

Clause 7.1 requires that the planning process include identification of the inter-related processes (i.e., monitoring, inspection, product quality objectives, testing, records of conformity needed to verify the product requirements have been achieved.

The bottom line:  the product characteristics, quality objectives and inter-related processes must be documented.  If this is not fully achieved in the design and development process (clause 7.3), it must be included in the product planning process (clause 7.1). Please see clause 4.1.

Please keep in mind that your company’s ISO registrar will require evidence of conformity (records/documentation) to verify the requirements of clauses 4.1, 7.1 and 7.3 have been met.

Bill Aston
ASQ Senior Member
Managing Director of Aston Technical Consulting Services
Kingwood, TX
www.astontechconsult.com

For more on this topic, please visit ASQ’s website.

ISO 9001 7.1 Product Realization

Suppliers, supplier management

Q: Our company, certified to ISO 9001:2008 Quality management systems–Requirements, is experiencing quite a bit of supplier non-conformance.

An option we are interested in is to have a set of manufacturing drawings for our suppliers and a set of inspection drawings. Either the manufacturing set would require tighter tolerance than the inspection set, or the inspection set would have looser tolerances than the manufacturing set.

What would the criteria be to introduce this theory into our procedures?

A: I suggest that you consider the point of ISO 9001:2008 Quality management systems–Requirements, clause 7.1, regarding the development of product objectives. Your planned approach is similar to what is intended by this clause.

The organization should set its product requirements during the product planning stage. Product requirements should be based upon design inputs, outputs, verifications and validations. This provides the essential measurements (tolerances) required for the product to function as designed or intended.

The requirements sent to suppliers, or to the shop floor, should be within the design tolerances or criteria, but not necessarily the same. However, in the event that inspection or a supplier identifies/provides a product that is outside the drawing requirements, it would be up to the engineer or the designer to decide if the product still meets the design criteria. If so, the product would be disposition “accept as is” and would still function as planned.

If repetitious non-conformance is encountered and the product is still within the design criteria, then changes to the supplier and inspection criteria should be considered to prevent continued non-conformance. If the non-conformance does not meet the product requirement or the design criteria, corrective action should be taken with the supplier.

Bill Aston
ASQ Senior Member
Managing Director of Aston Technical Consulting Services
Kingwood, TX
www.astontechconsult.com

For more on this topic, please visit ASQ’s website.