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 either takes place at the end of the production line (e.g., inspecting a sampling of parts within a lot/batch or of a single part representative of a first production lot/batch (i.e., a First Article Inspection) or at a specific point in the process (i.e., in-process inspection).

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 the 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 can 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,

When scheduling an Inspector to visit a supplier for a “Source Inspection”, the following information should be provided to the Inspector:

1. Supplier contact name, phone number, and e-mail address
2. Purchase order number
3. Item number
4. Part number
5. Quantity of parts to be inspected (or a specified AQL or AOQL)
6. Date source inspection is required
7. Types of inspection required
   • In-Process
   • Final
   • Interim (i.e., a period of time between events)
   • First Article Inspection (FAI)

An Inspector will often choose to take portable measurement instruments, with a known calibration status, to the supplier site. If larger equipment is required, then the Inspector would need to either use or witness an employee, performing the measurements using the measuring instruments owned by the supplier. These arrangements should be made in advance.

In addition, when measurement instruments owned by the supplier are used for the source inspection, the Inspector “should” verify that the supplier has maintained their calibration status throughout the production lot/batch.