Tag: inspection

Ever wonder what happens during a product quality inspection?

Pro QC’s Shenzhen, China office provides an on-site demonstration of in-process and pre-shipment quality inspections.


Comments and suggestions are always welcome and appreciated!  Our goal is to provide valuable content to those interested in learning more about quality related concepts and processes that we have over 20 years of experience providing.

Acceptance sampling isn’t scary

As it turns out, a significant number of people find the Pro QC site searching for sampling and sampling related terms such as ANSI Z1.4 or MIL-STD-105E  (no longer in use).  In speaking with organizations, I’ve also detected a certain level of fear regarding how to approach an acceptance sampling strategy.

Fear is unnecessary… In fact, sampling here is nothing more than a tool you’re going to use to provide a realistic (of course statistically relevant) assessment of quality and be able to ultimately determine whether or not product is meeting expectations without having to spend the time and money involved with a 100% inspection.  This is a good thing.

Some advice…

Get your specs straight – Before you even start to think about AQLs and defect classifications, go back and make sure you’ve really evaluated your product and have created detailed product specifications.  Once you have this information, go through each item and determine how you want to classify nonconformance (major, minor or critical).  At Pro QC, we use the following general guideline for defect classifications:

  • Critical – Any condition found which poses the possibility of causing injury or harm to, or otherwise endangering the life or safety of, the end user of the product or others in the immediate vicinity of its use.
  • Major – Any condition found adversely affecting the product’s marketability and sale-ability or adversely affecting its required form, fit or function and which is likely to result in the end user returning it to the source from which is was purchased for refund or replacement.
  • Minor – Any condition found which while possibly less than desirable to the end user of the product, does not adversely affect its marketability, sale-ability, form, fit or function and is unlikely to result in its return to the source from which is was purchased.

Special or General? – The ANSI Z1.4 tables show various sample sizes based on lot (batch)  sizes in relation to Special and General levels. Here, you’ll want to go through your spec and determine what would require higher levels (general) of sampling or lower (special).  For example, if you have an electronic product that requires functional testing (need to make sure it turns on maybe), special levels of testing makes sense because it may be considered destructive.  The same goes for drop-testing to determine the packaging integrity.  Time is an obvious important consideration, as it relates to not only cost but to shipment schedules as well.  An example might look like this:

  • Visual (cosmetic/workmanship) inspection – General Level 1
  • Drop-testing (Package integrity ISTA testing) – Special Level 3
  • Functional Testing – Special Level 1

Single or Double? – Pro QC uses ANSI Z1.4 single normal sampling as a standard, but we have had clients request double.  If you look at the tables, you’ll note the difference is simply the number you look at.  So, it goes back to time and cost, but you’re also considering your level of assurance with the supplier in general.  You can look at less with double if the product meets expectations, but you’ll be taking a 2nd full sample set if not.

Know your AQLs – Acceptable Quality Limits are simply “the worst tolerable process average in percentage or ratio, that is still considered acceptable: that is, it is at an acceptable quality level.” To figure out what works best, play around with the numbers… Plug in your average lot sizes and levels and go through the row of scenarios.  What are you comfortable with?  An example might look like this:

  • Major Defects 1.5
  • Minor Defects, 4.0
  • Critical Defects 0.10

Tweak it – Sampling strategy is something that can grow and evolve with your product. As you develop supplier relationships and analyze inspection feedback, you’ll be able to make adjustments as necessary.

Utilize the experts – Of course, a 3rd party quality assurance provider such as Pro QC, can provide you with expert advice and guidance or even evaluate your product and develop the specs/sampling for you.  That both relieves apprehension and leverages expertise.

Note: International and national equivalents of the ANSI Z1.4 2003 standard exist as ISO 2859, NF06-022, BS 6001 and DIN 40080.

Product Inspection Strategy

A frequent question account managers receive is how to employ an inspection strategy to identify issues early and continue to ensure that product meets specifications.  Most agree that the tangible and intangible costs associated with poor quality support a preemptive strategy. The answer isn’t necessarily a simple one due to the variances involved in product specific requirements.  But, a general method of attack is suggested here:


Inspection Plan Development
A good plan is only as good as its foundation, so a comprehensive and detailed product specification is critical to the success of the overall strategy.  Pro QC often assists clients with this documentation creation and also uses it internally to direct engineers on-site.  A good plan incorporates anything that will affect the salability and performance of the product.


First-Article Inspections
Pro QC inspects first-article samples prior to volume production.  That means the product specifications are being met and reengineering won’t be necessary at an inconvenient point of time in the future.


In-Process Inspections
These on-site inspections evaluate samples of your products selected during the manufacturing process.  It confirms the quality of your product and allows any necessary changes to be addressed early on.  Incorporating these inspections reduces rework time and costs.


Pre-Shipment Inspections
During a pre-shipment inspection, engineers verify that the finished goods confirm to your specifications.  A representative sample is chosen randomly from the lot using a sampling plan such as ANSI Z1.4. The criteria is used to determine sampling levels and accept/reject determinations.


Inspection schedules are dependent on factors such past performance, so costs associated with preventative action are also reduced as performance becomes predictable and/or stable.  Continuous improvement and consistent results means investing in quality throughout the process and avoiding associated risks and cost in the future.