The effectiveness of handle insulated materials for reducing hand arm vibration among steel-plate polishing workers using air-angle grinders: A case study in an automotive part manufacturer, Chonburi province

Abstract

The use of metals is common in the automotive manufacturing industry as the main raw materials for various processes. These processes often involve the use of grinding and polishing machines, which can expose workers to vibrations that may have negative effects on their health. The main aim of this study is to investigate the levels of hand-arm vibrations experienced by workers using air-angle grinding machines to polish metal plates. The research seeks to develop a covering material for the handles, compare vibration measurements on the hand-arm before and after attachment of the covers, and assess the workers’ satisfaction levels post-attachment. To achieve these objectives, two different types of handle covers were designed and applied to the air-angle grinding machines used for polishing metal plates. Experiments were conducted with a sample group of 10 workers who met specific criteria. Vibration levels were measured before and after attaching the cover in the frequency range of 6.3-1250 Hz. along the X, Y, and Z axes. There search methodology involved the use of a questionnaire, Hand-arm meter, and the Wilcoxon Signed-Ranks test statistic to compare experimental results. The results showed a significant decrease in overall vibration acceleration after attaching both types of handle covers and grinding a 1 mm. thick steel plate for 2 minutes. The statistical significance level was P = 0.005. Before the experiment, the acceleration value was 4.97 m/s². After attaching material type 1, it decreased to 2.71 m/s², a reduction of 45.5%. Material type 2 resulted in a vibration level of 3.34 m/s², a reduction of 32.8%. Workers reported high satisfaction levels with material type 1, while material type 2 received a moderate rating. In the discussion, It was noted that although attaching the handle covers reduced vibration levels, they still exceed the standard threshold of 2.5 m/s² that necessitates action. It was suggested that different grip postures or handle thicknesses could potentially impact the level of hand-arm vibration exposure.