Visual Inspection Reliability for Precision Manufactured Parts.
OBJECTIVE
Sandia National Laboratories conducted an experiment for the National Nuclear Security Administration to determine the reliability of visual inspection of precision manufactured parts used in nuclear weapons.


BACKGROUND
Visual inspection has been extensively researched since the early 20th century; however, the reliability of visual inspection for nuclear weapons parts has not been addressed. In addition, the efficacy of using inspector confidence ratings to guide multiple inspections in an effort to improve overall performance accuracy is unknown. Further, the workload associated with inspection has not been documented, and newer measures of stress have not been applied.


METHODS
Eighty-two inspectors in the U.S. Nuclear Security Enterprise inspected 140 parts for eight different defects.


RESULTS
Inspectors correctly rejected 85% of defective items and incorrectly rejected 35% of acceptable parts. Use of a phased inspection approach based on inspector confidence ratings was not an effective or efficient technique to improve the overall accuracy of the process. Results did verify that inspection is a workload-intensive task, dominated by mental demand and effort.


CONCLUSIONS
Hits for Nuclear Security Enterprise inspection were not vastly superior to the industry average of 80%, and they were achieved at the expense of a high scrap rate not typically observed during visual inspection tasks.


CONCLUSIONS
This study provides the first empirical data to address the reliability of visual inspection for precision manufactured parts used in nuclear weapons. Results enhance current understanding of the process of visual inspection and can be applied to improve reliability for precision manufactured parts.
Sandia National Laboratories, Albuquerque, New Mexico jesee@sandia.gov.
Judi E
JE
See
D000328:Adult; D001288:Attention / Q000502:physiology; D003625:Data Collection; D006801:Humans; D008420:Manufactured Materials / Q000592:standards*; D066192:Manufacturing Industry / Q000592:standards* / Q000706:statistics & numerical data*; D008875:Middle Aged; D015203:Reproducibility of Results; D013647:Task Performance and Analysis; D014796:Visual Perception / Q000502:physiology; D016526:Workload / Q000592:standards* / Q000706:statistics & numerical data*; D055815:Young Adult
human error analysis; mental workload; reliability issues; signal detection theory; stress; visual inspection