Experimental study of cognitive aspects affecting human performance in manual assembly

This full factorial experimental study aimed to investigate different ways of presenting material and information at the workstation while using mixed assembly mode with product variants. The experimental set up annotated an assembly line involving 36 subjects (19 women and 17 men) partly assembling a pedal car. The material presentation factor involved the use of a material rack compared to using an unstructured kit as well as a structured kit. The information presentation factor involved using a text and number instruction compared to a photograph instruction, and situations with and without component variation were considered. Both quantitative and qualitative results were obtained, including time and errors as dependant measures, and workload ratings as well as a questionnaire as support measurements. Among the results it was found that assembly times and workload ratings were lower when using a kit, whereas using a material rack resulted in perceived decreased workflow and increased stress and frustration. Moreover, assembly times and workload ratings were lower when using photographs, whereas using text and numbers increased mental workload. The results could be useful when planning work places and production systems in order to obtain a better workflow and an increased human performance.