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Operator mental models in contemporary manufacturing: A comparison CNC lathe and EDM control
Abstract
Changes on the shop floor require machine operators to develop skills and expertise to perform tasks that have more cognitive complexity. The literature in human machine systems suggests that operators develop elaborate mental models that influence all aspects of their interaction with complex manufacturing systems. Research on the human factors issues in manufacturing is in its infancy, and none of this research has focused on operator mental models. Therefore, this research investigates the operator mental models when they control CNC lathe and EDM. The goal of this research is to identify and understand cognitive issues that may be used to improve the design of advanced manufacturing technology (AMT). This research consists of two sequential studies, study 1 on CNC lathe control and study 2 on EDM control. Study 1 required five experienced machinists to verbalize or "think aloud" while controlling a CNC lathe while study 2 required nine experienced tool makers to verbalize as they created a mold cavity using an EDM. Study 1 examined two VPA methods and found that concurrent VPA was better suited for shop floor activities than retrospective VPA. A hybrid approach with concurrent VPA as the primary method and retrospective VPA as the secondary methods was used in study 2. The verbal data was transcribed, segmented, encoded, and analyzed along with operator control behavior to derive mental models. These mental models for both tasks were compared and contrasted. The verbal protocol data was used to identify similarities and differences in operator control behavior for CNC lathe and EDM. Operators had elaborate mental models of part geometry and the manufacturing processes needed to achieve the desired shape. Operators used exploratory learning as their primary problem-solving strategy. Operators used rough and finish machining strategies to adjust the trade-off between input and output parameter setting in EDM only. During each machine tools automatic cycle, the operators demonstrated elaborate mental models of monitoring and trouble-shooting. This was especially important for EDM, where the operators were continually adjusting process parameters to maintain stable machining conditions. These core mental models were used to derive guiding principles for AMT user interface design. These principles were developed into concept for interface tools that need to be developed and studied further.
Subject Area
Industrial engineering|Occupational psychology
Recommended Citation
Batra, Sanjay, "Operator mental models in contemporary manufacturing: A comparison CNC lathe and EDM control" (1996). ETD collection for University of Nebraska-Lincoln. AAI9715952.
https://digitalcommons.unl.edu/dissertations/AAI9715952