Workers’ Eye Movements During the Manufacturing of VaRTM Preforms

Abstract

Many companies are currently researching VaRTM molding method for practical application in the composite material industry, such as in wind-powered power generating equipment, boats and ships, and aircrafts because it can produce moldings with complicated shapes or large sizes, does not require a large amount of business investments, and can make molding cost efficient. However, it is difficult discovering the optimal conditions for molding, as VaRTM molding requires perform manufacturing process which makes the fiber base material fit into a three-dimensional shape by applying pressure and heat. It is said that the accuracy of the preform affects the mechanical properties of the molding product. In recent years, despite continued investigations into the automated manufacturing of preforms, the majority of preforms are still manufactured by the hands of workers, causing the accuracy of the preform to be dependent on the ability of the worker. In this research, we made three subjects with varying number of years’ experience create preforms and produce a VaRTM molding. Conducting an interlaminar shear strength test on the molding products revealed that they had a higher intensity in order of the most years of experience to least. In order to identify the reason why the accuracy in creating a preform is dependent on the ability of the worker, we informed all of the subjects of the work process beforehand, made them use the same tools and fiber base materials, and investigated the differences in manufacturing method and manufacturing techniques caused by the workers’ number of years of experience. Differences were observed in the expert and non-experts from an overall image of the subjects when working, such as how they handled the tools (iron), their posture when layering, how they exerted strength into layering, etc. We also measured the subjects’ eye movements, focusing on where they were looking. Rather than analyzing the amount of time and the movements of their entire bodies in each work process, instead, we focused on the movements of their line of sight when working. Thus, we compared where each of the subjects was watching and the order in which they watched them. Furthermore, as well as the movement of their line of sight, we also focused on how they moved their hands when conducting the work and investigated the coordination of all of the subjects when working. Based on the fact that there were differences in the accuracy of the preforms, it is clear that manufacturing preforms is not a general concept in which the technique is handed down. While optimizing the creation of systems, work instruction manuals and tools which produce exactly the same accuracy, regardless of the worker manufacturing the preform, we will continue to conduct research that leads to the development of automated production technology.