When discussing quality assurance standards, the focus is usually on the general requirement that the organization shall establish, implement and maintain a quality management system and continually improve its effectiveness. The process for this is the classic Plan-Do-Check-Act, which embodies a culture of planning, monitoring and improving organizational performance. The "Check" element in this process includes monitoring and measuring the processes or product against the policies, objectives and product requirements, and then recording the results. The monitoring and measuring of the product is a Quality Control activity, usually referred to as product inspection. Inspection and inspectors are key elements in engineering companies and existed even before mandated quality assurance standards became commonplace. There is a risk that in focussing on planning and documentation aspect of Quality Management, we can understate the importance of good inspection. Planned and documented quality systems, procedures and instructions are essential, and accreditation may be required by most customers; but customers buy the parts, not the quality system. A conforming part is the objective of the quality system and it is vitally important that we undertake the necessary quality control to verify that parts conform at all stages of the manufacturing or maintenance process. This is particularly relevant when we are using special manufacturing process; i.e. those that we cannot verify by final inspection. Special processes include but are not limited to shot peening, heat treatment, chemical processing and non-conventional machining processes. Inadequate inspection is often a major non-conformance during special process audits and, if undetected, can lead to part failure with the resulting consequences and potential liability for the processor.
The most widely used quality standard ISO9001:2008 makes an explicit requirement to determine inspection requirements for the part at the planning stage of manufacturing and how the inspection results are to be recorded (paragraph 7.1). The aerospace version of this standard, AS9100C, includes this and adds more specific detail in the following paragraphs:
7.1 & 7.3 The planning and design stages must consider how the parts are to be inspected.
7.4.2 Purchasing information for materials or parts shall specify inspection requirements at both supplier and receiver ends (at dispatch and reception of the goods respectively) as appropriate.
7.5.1 Production work instructions must include inspection documents, evidence that inspections have been done, and defined inspection points within the production process.
Aerospace maintenance standard AS9110 also includes these specific requirements.
A first article inspection report (FAIR) is often required when parts are manufactured by a supplier for the first time. This is to validate all the production processes and it requires a fully conforming part along with all the supporting documentation, including inspection and test results. Where some of these inspections are subsequently established in the normal production processes, they must be carried out to the same procedure and standard of accuracy as in the FAIR. A customer may issue their own requirements for the format of a FAIR, but there is also a standard compiled by the International Aerospace Quality Group (IAQG), AS9102.
Special processes in the aerospace, transportation and medical industries are often audited using the Nadcap checklists, which are compiled by representatives from the major end-users, auditors and specialists in the relevant industries. For example, shot peening is audited to the audit criteria AC7117 series of checklists. There is a checklist for common requirements and individual checklists for various peening techniques - automated, computer controlled, forming, flap peening and manual peening. These checklists scrutinise all aspects of the relevant operations including inspection processes and verify their effectiveness. An auditor may observe the supplier's inspection of a part and then re-inspect the part himself. In this way, the competence of inspection is examined, and any failure would normally be a major non-conformance as it has direct effect on the quality of the product.
The competence of the inspector is vital. Even if procedures and documents all conform, the effectiveness of the process is determined by the inspector's capability to detect any flaw or deviation from the requirements. Inspectors must be trained by an experienced person who has proven capability and the qualifications to inspect should be documented. Inspectors usually have a different stamp to authorize documents than do an operator. If the operator is also qualified to inspect, then this must be clearly documented and a secondary or final inspection by another qualified person is recommended. The inspector's competence should be assessed by practical inspection tests and reassessed, normally within twelve months of the previous assessment.
Quality management has progressed significantly over the years, with better written standards, more competent auditors, and greater quality awareness in the workforce and management. But deviations can and do occur; effective in-process inspection is essential to provide confidence in process quality and final inspection is the safety net to prevent non-conforming parts from escaping.

For questions contact paul@mfn.li

Standards Forum
by Paul Huyton,
MFN Course Director World Wide
more information at www.mfn.li/trainers