VOL. 24 March ISSUE YEAR 2023

Standards Forum

in Vol. 24 - March Issue - Year 2023
Up-Issued Shot Peening Specifications

SAE AMS2432 Rev E.
A five-year review of Aerospace Material Specification AMS2432 for Shot Peening, Computer Monitored has recently been completed and is now issued by the SAE at Rev. E. AMS2430 for Automated Shot Peening remains an integral part of AMS2432 and must continue to be used in conjunction. The changes incorporated are varied and, in some cases, may require modifications to existing computer-controlled plant. For example, the frequency with which the process monitoring computer must check for out of tolerance conditions is now specified. Also the specified shutdown tolerances and limits have been changed but not necessarily tightened, however, the out of tolerance process condition shutdown delay has been loosened slightly. An in-depth review of any computer-controlled equipment, operated to the requirements of AMS2432, would be prudent to ensure continued compliance. Assessing the control tolerances could also prove beneficial to production efficiency. Media control remains principally with AMS2430, however, there are now specific references to control within AMS2432, and to prevent cross contamination between media type and hardness. A potentially significant change is that peening media shape may now be controlled offline, however, size control remains an in-line requirement. In conclusion, the revision drives further improvement in the control of the process but not through the tightening of controls. It appears to be a fine tuning to improve the efficiency of the process, while still maintaining high standards.
The AMS2430 specification should be approaching the 5-year review deadline, and for those who have a vested interest in the process, input can be given either via the SAE website, and the details of which are given on the AMS specifications. Input can also be achieved by attending the review meetings. The development of specifications benefits hugely from input not only from a Cognizant Engineering Organization (CEO) but also the shot peening contractors who process significant aerospace components to the AMS specifications. A wealth of experience is held within the subcontract organizations providing shot peening services especially those that contract for a large variety of CEOs. It is therefore potentially of great benefit to the specification enhancement process when subcontractors become involved in the development process.
NADCAP - Surface Enhancement AC7117. 
AC7117 is now at revision D and the subset of checklists is now at revision C. Work continues with the development of the family of Nadcap shot peening checklists, and there are a number of changes and a review of these changes, sooner rather than later, might prove beneficial, depending on who your subscriber customers are. The most significant is that AC7117 now includes detailed instructions relating to the number of Job Audits required, in relation to the number of and type of machines being employed under the various shot peening disciplines. These criteria apply to all the disciplines covered by the checklists, including peen forming, automated peening, manual peening, etc. These changes are very likely to result in a day or possibly even two, and being added to the original duration of the audit, this though, will depend on the size of the facility. For large facilities, there could be more than one or two days added. Many of the changes to the checklists are clarifications, achieved by the rewording of the requirements. Various questions relating to mechanical cleaning after peening have been added, and these are OEM specific and should be reviewed to confirm applicability. There are also other new OEM specific questions added. OEM specific questions are incorporated since the AC7117 family of checklists do not specifically cover key areas of importance to some of the subscribers to the Nadcap process. The original intention to have an all-encompassing checklist that satisfied all subscriber requirements has not been achieved. The Auditor’s handbook has also been updated in line with the revised checklists.
As with the development of AMS specifications, it is worth mentioning that to design a balanced, productive shot peening Nadcap auditing process, it is beneficial that those providing the shot peening services are involved with the checklist development process. The Nadcap Checklist development process is not restricted to the subscribers, and representatives from the Shot Peening shops are welcome to attend the meetings. The meetings are held in various locations 3 times a year. During the meetings, discussions are held regarding auditor performance and auditee-based issues. At these times, access is restricted to subscribers only, which often presents the opportunity to meet other peening shop representatives. A major benefit of attending the meetings is the opportunity to understand changes to the requirements, which are planned to be flowed down in future renditions of the checklists before they become live. This gives shot peening service providers the opportunity to get ahead by making changes (which can be significant) before they become formal requirements.

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MFN Contributing Editor

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