Use of Ergonomics as a Quality Improvement Tool in a Manual Assembly Task

Abstract

This study attempted to identify a direct relationship between the design characteristics of a manually-assembled product, exposure to work-related ergonomic risk factors, and improvement in product quality. The study considered (a) Accessibility (ease of approach) and Guidance (ease of alignment and positioning) as Design Variables, (b) Shoulder Abduction, Trunk Lateral Flexion, Rate-Normalized Percentage of Maximal Voluntary Contraction (%MVC) of the Wrist Flexors, Wrist Extensors, and Deltoids, and Frequency of Attachment as Ergonomics Variables, and (c) Percentage of Attachment Too Loose, Too Tight, and Misaligned as Quality Variables. Postural data, surface EMG data, and quality data were collected from 10 participants performing four 10-min repetitive manual assembly tasks with plastic threaded nuts, bolts, flat parts, and open-box parts. Unobstructed accessibility of manually-assembled parts was associated with decreased exposure to awkward trunk posture, decreased activity of the wrist flexors and extensors, increased frequency of repetitive motion, and a decrease in the tendency to attach parts too loosely. Accessibility had no effect on misalignment defects as measured. Part guidance decreased the number of parts attached too tightly and aided in increasing the rate of assembly of parts when there was unobstructed access to parts.

Ergonomics and quality in paced assembly lines

“…Specifically, Eklund's quality deficiencies were caused by excessive physical demand, designs that made assembly difficult, and psychologically demanding tasks (Drury, 2000). In a laboratory study at University of Utah, Wick and Bloswick (1998) had 10 participants assemble components under different detailed component design conditions. The conditions that allowed the best body postures also produced the best quality.…”