The objective of quality assurance and process control is to consistently and repeatedly meet the customers’ requirements. To this end there will be considerable investment in procuring the necessary equipment and materials, also in developing the correct manufacturing procedures. In recent times, it has been widely recognised that investment in operator’s skills and knowledge is also required. Many customer specifications will include training requirements for the qualification and requalification of operators. All other investment may be wasted if the operator doesn’t have the competence to undertake the activity correctly and, in most cases, verify the process outputs.

Shot peening is classified as a “special process” in manufacturing. This means that after processing, the parts cannot be non-destructively tested or inspected to prove that they conform to the requirements of the specification. Some aspects of the process are counter-intuitive and specific technical knowledge is important. So relying on “common sense” and general manufacturing knowledge is insufficient to achieve the required outcome. Specific training and qualification is generally recognised as vital to a successful outcome. Processors should, as a minimum, adhere to the training requirements laid-down by their customers. 

Proprietary customer specifications may include operator qualification requirements, either directly or indirectly by invoking the industry standard AMS 2430. The customer’s contractual requirements may also include holding Nadcap approval. The Nadcap audit criteria AC7117 gives requirements for operator qualification and requalification, so the operator’s standard of competence is being well defined by the customer. If there are no specified training requirements, then reference can be made to requirements available in these industry specifications.

The documents identified above are in the public domain and obtainable. AMS 2430 can be purchased from the SAE website and AC7117 is available by registration on the eAuditnet.com website. Good use can be made of external training providers with specialised knowledge of the process and training requirements. MFN Shot Peening training has three levels and is designed to satisfy all the specified and implied requirements for theoretical training. There is also a full day course for Rotary Flap Peening qualification to AMS 2590 and proprietary requirements. The courses have third-party acceptance from the Federal Aviation Administration (FAA) and include the option for a written test as proof of theoretical competence. The Rotary Flap Peening course also has individual assessment of practical skills as an element of the qualification.

The operator qualification requirements in these industry documents and the MFN training are broadly as follows.

The underlying theory and principles of how peening works.

Key process measurables: Intensity and Coverage.

The equipment and techniques for measuring and inspecting Intensity and Coverage.

Media types, selection and quality control.

How process variables will affect the Intensity and Coverage.

Developing and qualifying a peening process.

Workshop procedures and documentation.

Quality assurance and control of the process.

How to proceed when requirements have not been achieved.

These basic topics will be supplemented by associated modules to provide the necessary process knowledge for operators, supervisors, inspectors, auditors and support engineers. The three levels of the MFN training programme provide the appropriate level of understanding according to job responsibilities. Some proprietary customer specifications also break down the training requirements according to job function. The Rotary Flap Peening course includes a written test and individual practical assessments to validate the qualification, as is required by the specification.

Requalification.

It is very important that competence does not degrade over time and that no unacceptable practices gradually evolve, so there is a need to requalify operators, usually at no more than a twelve-month period. This annual requalification is the Nadcap AC7117 requirement and is included in many customer specifications. Some of these specifications specify the full training, as for initial qualification, others something less. The most common is to have an assessment by a qualified person of the operator undertaking a production job. The individual skills required for a conforming job can be witnessed and recorded. Along with a short written test to confirm process understanding, this then can be a signed-off requalification. A repeat of the MFN training can be used for the theoretical aspects; repeating the training every twelve months for this purpose can normally be provided at a discounted rate.

Details of MFN training can be found at www.mfn.li/workshop. On-site training can also be provided.

Standards Forum

by Paul Huyton,

MFN Course Director World Wide

more information at www.mfn.li/trainers