Experiment on influencing factors of cutting force of blades of trim tool for longan branch

In order to reduce cutting force of blade and improve cutting quality of mechanical pruning machinery, using "Shixia" branch as experimental material, cutting test was conducted in the accurate micro-controlled electronic universal testing machine with a self-made cutting device. An investigation was undertaken to study the effect of branch diameter, cutting speed, cutting gap, blade bevel angle and edge curve on the peak cutting force of moving blade. Average value of the peak cutting force was increased from 0.67 to 4.13 kN as the branch diameter was increased from 10.58 to 29.43 mm. When the cutting speed was increased from 20 to 500 mm/min, average value of the peak cutting force was decreased from 2.19 to 1.76 kN. Average value of the peak cutting force was decreased linearly as the cutting gap was increased from 0.05 to 0.5 mm and then slowly increased as the cutting gap was increased from 0.7 to 2 mm. As the blade bevel angle was increased from 5° to 30°, average value of the peak cutting force was increased from 1.88 to 3.26 kN. Cylindrical curve edge blade was the most force-saving with cutting off branch of the same diameter. The relevant changing trends of the peak cutting force and cutting parameters were analyzed with statistical software. The results showed that there was an significantly positive power function correlation between the peak cutting force and branch diameter, significantly negative logarithm function correlation between the peak cutting force and cutting speed, two polynomial function correlation between the peak cutting force and cutting gap and significantly positive exponential function correlation between the peak cutting force and blade bevel angle. Factors and levels of the orthogonal experiment were selected based on the single-factor test. Cutting speed, cutting gap and blade bevel angle were selected to perform the orthogonal experiment with the peak cutting force of moving blade as the test index. The orthogonal experiment results showed that the optimal combined parameters were as follows: cutting speed of 500 mm/min, cutting gap of 0.9 mm and blade bevel angle of 10°, at these conditions, the minimum cutting force for cutting off branch was 1.58 kN. These results indicate that the optimization of cutting speed, cutting gap and blade bevel angle will result in significant force saving and increasing efficiency of mechanical pruning machinery.