A “Source Inspection“ is different from a “Supplier Audit” (or Product Audit) because it is an “inspection” (not an audit). Unlike a Supplier/Product Audit (which follows a product through its entire production process – verifying that requirements have been met), a Source Inspection takes place at the end of the production line and usually involves a much larger sampling of finished products (based on the AQL or AOQL selected).

The AQL is the “Acceptance Quality Limit”… which is defined as the “quality level that is the worst tolerable process average” (Ref. ISO 2859-1:1999, sec. 3.1.26). The AQL is normally based on sampling tables contained in either ASQ/ANSI Z1.4 or Z1.9 Standard. The AOQL is the “Average Outgoing Quality Limit” and is typically based on tables contained in the book ”Zero Acceptance Number Sampling Plans“, (Fifth Edition) by Nicholas L. Squeglia.

The most practical difference between choosing an AQL or AOQL is that the ASQ/ANSI Z1.4 & Z1.9 Standards allow a certain number of defective products to be identified in the sample, and the entire lot/batch still be accepted. In contrast, when using the sampling approach described in the book ”Zero Acceptance Number Sampling Plans“, if a single defect is found, then the entire lot/batch must be rejected and undergo a 100% inspection.

A “Source Inspection” typically involves verifying:

• that the product characteristics comply with those specified on an Engineering drawing (along with any specifications invoked), and could also include non-destructive testing.
• the raw material certifications (e.g., Certificate of Analysis, Material Test Reports) supports that the material used complies with the requirements for the finished product.
• that any “Special Processes” are supported by certificates from the processing operation (whether in-house or outsourced). The Aerospace industry usually requires those special processes to be Nadcap accredited.

A “Source Inspection” is similar to an AS 9102 First Article Inspection (FAI)… except that, unlike a FAI, the “Source Inspection” report would include the results of all of the products inspected (i.e., included in the sample).

A Source Inspection “may” replace the Receiving Inspection performed by the customer.

(e.g., from multiple shifts and multiple workers). So the likelihood of a nonconformity being identified during a Source Inspection is greater than what might be found during a Supplier/Product audit.

While the Supplier/Product Audit may seem similar to a Source Inspection, the major difference between the two is that if a nonconformity is found during a Source Inspection, then it is up to the company (supplier) to figure out the source/cause of the nonconformity. However,