QMT Features: August 2014
Measuring the progress of a new Nadcap Task Group
In the January/February 2013 issue of QMT, a new Nadcap Task Group for Measurement and Inspection was introduced. In this update, we take a closer look at this activity and why it matters


Measurement and inspection processes are used throughout the aerospace industry to verify compliance to the specification. It is the same in other industries where precision engineering is critical to ensuring output that meets the requirement. In aerospace, product not meeting the requirements detailed in the specification is a major contributor to quality issues. Failure to accurately identify deviations can lead to product performance degradation; reduced life; in-service issues; sub-optimal product competitiveness; manufacturing and/or assembly problems; and increase in production costs or lead time. Ultimately, this can even lead to part failure which is unacceptable for critical industries such as aerospace where the consequences can be catastrophic. 

Ensuring the effectiveness of measurement and inspection processes involves a number of activities, such as calibration, product definition and interpretation of requirements; inspection planning and feature coverage; equipment and measurement process validation; and not least, staff competencies. Nadcap data across a number of different audit areas indicates that personnel change has a significant impact on operations – ensuring consistently excellent staff performance should not be overlooked when evaluating improvement opportunities.
Despite the controls facilitated by supplier contracts and international standards, few of these processes are audited at a detailed industry-wide level. The aerospace industry determined that, while standards such as AS9100 cover some of the processes, they are not audited in sufficient detail to demonstrate full control. Instead, there is reliance on the supply chain to self-regulate and provide technically detailed processes with little or no oversight from the customers. 
This has been shown to result in several potential issues. For example, a coordinate measurement machine (CMM) was being used to measure the features of an aerospace component. Inspectors reviewed the output of a CMM and detected an incorrectly programmed feature tolerance (0.01 instead of 0.001). Failure to implement a robust CMM program validation process can lead to non-conforming parts being shipped to the customer so this generated a number of questions that required investigation, such as: 
  • Is the correct datum system set?
  • Has the drawing been interpreted correctly?
  • Has the CMM been programmed correctly?
  • Has the CMM been calibrated? 
  • Has the CMM stylus been qualified correctly? 
  • Are the results in error real or are they due to poor measurement?
Aother example relates to equipment validation. A micrometer was being used to measure a shaft diameter. The shaft had a diameter tolerance requirement of 50mm +/- 0.020mm. No gauge Repeatability and Reproducibility (R&R) study was performed to confirm that the micrometer was fit for purpose. When this study was carried out, it indicated a very high gauge R&R of 132%, raising doubt over the conformance of historically delivered product. Failure to verify equipment capability before use or to conduct an in-service check of historically manufactured components can also lead to defective product being sent to the customer.The criticality of measurement and inspection processes, combined with the lack of effective oversight, led the aerospace industry to identify Nadcap as the way forward. With a history of supporting industry collaboration to ensure effective oversight of critical processes, the Nadcap program had both the expertise and the infrastructure to support this effort. In October 2012, the Nadcap Management Council approved Measurement & Inspection as a formal Nadcap Task Group, chaired by Rolls-Royce plc, with active participation from others such as Airbus, The Boeing Company, GE Aviation and SAFRAN.Since then, the first checklists have been released. As Nadcap is not an engineering standards organisation, the audit criteria are based on industry standards and company-specific requirements as appropriate, but do not create additional requirements. The core checklist AC7130 - Nadcap Audit Criteria for Measurement & Inspection Accreditation Program covers quality systems; calibration; software; competencies; visual acuity; environments; validation; and planning. AC7130/1 - Nadcap Audit Criteria for Measurement & Inspection Coordinate Measurement Machines (CMM) was also  released in late 2013. This year, the Task Group is working to develop and issue additional checklists focused on Airflow Testing and Laser Trackers, as well as to identify and contract with auditors qualified to conduct these audits. Further checklists regarding Articulated Arms, Manual Gauges and Non-Contact Fringe Projection are being considered for future development.For more information on this activity, or to find out how to get involved, please contact James Bennett, Senior Staff Engineer at jbennett@p-r-i.orgwww.p-r-i-.org
  
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