Optimization of the operating parameters of a grass trimming machine.

Hand-arm vibration syndrome (HAVS) is very common among the workers operating power tools and doing similar nature of work for long hours. Grass trimming is one of the operations that involves use of vibrating cutter, and results in hand-arm vibration among workers. In this study, the influence of several operating parameters (length of nylon cutting thread, engine speed and handle material) is investigated in terms of HAV. Data are analyzed via orthogonal array, main effect, signal-to-noise (S/N) ratio, and analysis of variance to determine the appropriate operating parameter levels to minimize HAV. Operating parameters under investigation are found to be influential in controlling HAV generation during grass trimming operation. Experiments are carried out for measuring hand-arm vibration using tri-axial accelerometer conforming the effectiveness of this approach. Results show that 100mm length of nylon thread, 3000+/-400rpm of engine speed and ABS handle material combination results in minimum HAV (HARM) of magnitude 2.76m/s(2). Through this study not only the optimal operating parameter levels for GTM are obtained, but also the main process parameters that affect the HAV are determined. The optimum HAV obtained through appropriate level selection of operating parameters, significantly reduces the occurrence of HAVS among the grass trimmers.