Visual Inspection Reliability for Precision Manufactured Parts

Abstract

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.Method: 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 workloadintensive task, dominated by mental demand and effort.Conclusion: 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.Application: 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.

Challenge to Collect Empirical Data for Human Reliability Analysis—Illustrated by the Difficulties in Collecting Empirical Data on the Performance-Shaping Factor Complexity

“…Debugging: an analysis of Bug-location strategies [37] Generation of and location of erroneous line of code in programming Hitting the wall: errors in developing and code inspecting a "simple" spreadsheet model [38] Task is to build and code a spreadsheet model. Visual inspection reliability for precision manufactured parts [39] Visual inspection of manufactured parts used in nuclear weapons (accept or reject correct and defect parts). manipulated this).…”

The Role of Visual Inspection in the 21st Century

“…With the rise of human factors/ergonomics (HFE) came the study of not just how well people can perform visual inspection tasks, but how their roles in the system could be modeled to predict performance during systems design. Studies of industrial inspection were undertaken for a variety of products, combining detailed observations and interviews with measurements of defect detection performance, a tradition that continues today (See, 2015). The two theories most widely used in inspection are visual search theory and signal detection theory.…”

“…Visual inspection has been extensively researched since the early 20 th century to understand the factors that impact performance (See, 2012;See, 2015). The most frequent and consistent observation is the imperfection of human inspectors.…”

Application of hidden Markov models to eye tracking data analysis of visual quality inspection operations

“…Khasawneh et al (2003) attract attention to the inspection task during quality control, particularly the search portion and use of eye-tracking technology. See (2015) provides the first empirical data to address the reliability of visual inspection for precision manufactured parts. In a recent study, See et al (2017) summarize the factors influencing inspection performance and suggest to explore new research areas in terms of visual inspection by considering automated inspection.…”