Effect of Product Structure on Manual Assembly Performance

Using Maynard's description, an assembly task may be divided into various task elements like reach, select, grasp, move, position, and assemble (Ghosh and Helander, 1985). Activities such as “reach” and “move” are governed by biomechanics of body motions including human factors principles such as Fitt's law. This research investigated the effect of the structure of the assembly and the type of assembly instructions on performance. Two different product structures were used — a vertical assembly, built bottom-up, and a hierarchical assembly, consisting of several subassemblies. Two different instruction strategies were used: 1. top-down sequential instructions 2. No Instructions. The research showed that vertical products were easier for manual assembly, when provided with instructions. For all three dependant measures, there was no interaction effect between the two factors, namely product structure and instructions. Average time for completion was significant for both factors i.e. product structures ( F (1, 20) = 4.417, p < 0.0485) and instructions ( F (1, 20) = 5.886, p < 0.0248). However, time for learning was significant only for product structure factor ( F (1, 20) = 5.239, p < 0.033). Also, trials to learn was significant only for product structure factor ( F (1, 20) = 4.449, p < 0.047).