Predicting tool operator capacity to react against torque within acceptable handle deflection limits in automotive...

Area of Science:

• Ergonomics and Human Factors
• Occupational Health and Safety
• Mechanical Engineering

Background:

• Threaded fastener tools are prevalent in auto assembly.
• Assessing tool handle deflection is crucial for operator safety and comfort.
• Existing psychophysical limits for tool handle deflection require validation through biodynamic modeling.

Purpose of the Study:

• To predict the proportion of tool operators capable of maintaining established threaded fastener tool handle deflection limits.
• To identify specific tool, task, and workstation parameters influencing tool handle deflection.
• To evaluate the effectiveness of a biodynamic tool operator model in identifying and resolving stressful tool installations.

Main Methods:

• A biodynamic tool operator model was developed and utilized.
• Parameters including tool geometry, speed, torque, mass moments of inertia, fastener torque, joint properties, and workstation distances were collected.
• Tool mass moments of inertia were measured using a novel rotating system device.
• Handle deflection was predicted for 35 tools across 69 installations in an auto assembly plant.

Main Results:

• Handle deflection exceeded established limits for six out of 69 evaluated jobs.
• The biodynamic model accurately predicted these exceedances.
• Modifications in tool speed and operator positioning successfully brought the problematic jobs within acceptable deflection limits, as predicted by the model.

Conclusions:

• Biodynamic tool operator models are effective tools for identifying stressful tool installations.
• These models can predict the efficacy of interventions aimed at improving ergonomic conditions.
• The study highlights the importance of considering tool, task, and workstation interactions in ensuring operator capacity and safety.