ERGONOMIC BASEDMODIFICATION OF HAND GRINDER TO IMPROVE PHYSIOLOGICAL RESPONSES, AND TO INCREASE PRODUCTIVITY AND USER SATISFACTION

Hand grinder is one of the tools used in manufacturing jobs, particularly for metal processing. Grinding is usually performed in the finishing process of a product, such as removing the ridges of welded joint. This tool has two main parts, namely the grinding disc and the electrical power motor for driving its spindle. Based on the work sampling in the several manufacturing shops, workers spent 20% of eight hours working time for grinding process. Observations and interview with several operators found some problems in the using of hand grinders such as fatigue and musculoskeletal complaints due to not ergonomic shape, size, vibration, and noise. This study aimed to improve a hand grinder design through ergonomic assessment. Twenty two parameters of assessment were identified by a questionnaire to 16 samples of hand grinder users. By considering those parameters and using the Microsoft Visual Basic 6.0, the ergonomic assessment software was created. The recommendations from the ergonomic assessment suggest that the hand grinders be modified by equipping them with two dumping covered handles. To determine the effects of the modification to the hand grinders, furthermore, the improved hand grinders were applied in the experimental research used treatment by subject design. Variables in the research were user physiological responses regard to musculoskeletal complaints, fatigue, energy expenditure, productivity and satisfaction. The research was conducted in March until August 2012 with 16 participated samples. The samples in the research were randomly selected from the students of Industrial Engineering Department of Atma Jaya Yogyakarta University. The data were analyzed statistically for descriptive analysis, normality test by Shapiro-Wilk, and the compare means analysis by t-paired test and Wilcoxon with significance level of 5%. The results of data analysis showed that the use of the modified hand grinder being yielded better results: 19.6% decrease in musculoskeletal complaints (p = 0.001), 17.7% decrease in fatigue (p = 0.004), 20.9% decrease in energy expenditure (p= 0.017), 15.97% increase in productivity (p=0.041) and 29.9% increase in satisfaction (p = 0.001). Empirically, it can be concluded that ergonomic based modification of hand grinders able to improve physiological responses in terms of musculoskeletal complaints, fatigue, energy expenditure, and increase productivity and user satisfaction.