Vibration Reduction for Electric Grass Trimmer : Mitigating the Risk of Hand-Arm Vibration Syndrome

Kang, Wen Xuan (2024) Vibration Reduction for Electric Grass Trimmer : Mitigating the Risk of Hand-Arm Vibration Syndrome. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

This report investigates the vibration analysis and mitigation strategies for an electric grass trimmer, aiming to enhance operator health and safety in the landscaping industry. This study evaluates vibration characteristics at the front and rear handles using 1/3 octave band graphs and acceleration spectra. The electric grass trimmer used in this research can generate 2.857m/s² of vibration, and can only be used in 6 hours and 8 minutes before reach the exposure action value. The average amount of time spent on operating hand-held grass-cutting machines was 5.5 hours per day in Malaysia, which is 2 to 6 hours. Hence, posing a significant risk of developing Hand- Arm Vibration Syndrome (HAVS). The installation a Tuned Vibration Absorber (TVA) effectively lowers vibration levels at both handle locations. Specifically, the vibration level at the front handle decreases from 2.5671 m/s² to 2.158 m/s² (15.94%), while at the rear handle, it decreases from 2.857 m/s² to 2.2481 m/s² (21.31%). Extended trimmer operation, from 6 hours and 8 minutes to 9 hours and 54 minutes, reduces operator risk of hand-arm vibration syndrome (HAVS). By identifying vibration modes and mode shapes, experimental modal analysis contributes to a deeper understanding of the trimmer’s structural dynamics. The amplitude of the front handle (P27) at 221 Hz in the FRF curves decreased from 4.20 m/s² to 1.25 m/s² (70.24%), while for the rear handle (P1), it decreased from 2.93 m/s² to 1.31 m/s² (55.29%). These results demonstrate TVA’s efficient reduction of vibration magnitude at 221 Hz for the electric grass trimmer.