Ergonomic and technical aspects in the redesign of material supply systems: Big boxes vs. narrow bins

Abstract

This paper presents a design stage comparison of an existing ‘big box’ material supply strategy common in Swedish manufacturing to a proposed ‘narrow bin’ approach common in Japanese production systems. Performance times, walking distances, layout space requirements were evaluated for 6 workstations using ‘big boxes’ of parts along the line. Biomechanical loading on spine and shoulder was estimated for one of the workstations. Comparisons were made to simulated layouts with the ‘narrow bin’ approach. The use of narrow bin supply yielded significant reductions in rack lengths (−81%), Material Areas (−61%), Walking Distances (−61%), Indirect Work (−24%), and Cycle times (−8%). Peak and cumulative spinal load estimates showed reductions from 29% to 65% with similar load reductions in shoulders and hands. The ‘narrow bin’ strategy also has implications for the material re-supply system, enables the use of flexible racking and can reduce lift-truck use. Work intensification may increase risks if time-gains are used only to increase direct assembly work repetitions. It is concluded that the narrow bin supply strategy has potential to both improve productivity and reduce risk characteristics of the system. Further field testing is required. Relevance to industry: Supplying materials in smaller narrower bins poses a potential ‘win-win’ design tactic with decreased operator risks and improved performance in final assembly when compared to ‘big box’ supply strategies. The final choice of strategy requires a context-specific assessment