Research Of Cutting Force For Reciprocating Knife Bush Harvester

Harvesting rich bush resources efficiently in our country, can supply sufficient raw material for the development of biomass energy, and also play a role in prevention of land desertification. Bush harvest machine in China is facing the problem of single species, low efficiency and poor targeting, which can't meet large area of bush harvesting requirement. In this paper, a bush reciprocating single blade cutting test equipment had made. Many tests had done with the self-made equipment in one-factor or multi-factor ways to study the influence of blade angle, sliding cutting angle, crank speed, bush moisture and bush diameter on the cutting force, which will lay the foundation for the development of efficient reciprocating bush cutter to meet the requirement of large area of bush utility.The test equipment is powered by hydraulic system, designed on the principle of slider-crank mechanism, adopted the structure of one-fixed-one-moving blade, and takes the advantages of virtual instrument. It can cut off single bush specimen and receive the size of cutting fore. Therefore, the relation between bush cutting force and test factors such as blade angle, sliding cutting angle, crank speed, bush moisture and diameter can be studied by the test.The results show that:the impact of cutter factor to cutting force in descending order is crank speed, sliding cutting angle, blade angle. There is a critical value and an optimal value in crank speed. The cutting is failed when the crank speed is under the critical value. There is little effect on the cutting force by continue improving the crank speed when it's above the optimal value. And the cutting force is significantly reduced by increasing the crank speed when it's between the two values. Both of values are proportional with bush diameter, and appropriate crank speed range of the large diameter bush is between 100r/min to 120r/min. The cutting force is proportional with blade angle, but the significant level is small. The blade strength is the major consideration on blade angle because the blade is easily damaged or even broken during the cutting process when the blade is small. When the blade comes to more than 45°, it is tough to cut and the cutting force is little increasing. Sliding cutting angle can enhance cutting force, but also let it down, which needs to take the diameter and crank speed into account. The appropriate range of sliding cutting angle for cutting bush is between 0°to 25°, and it should be decreased with the increase of bush diameter, otherwise, the bush specimen will slide toward outside during the cutting process, which would increase the cutting force, or even lead to fail in cutting off. Enhancing the crank speed will restrain the bush sliding and give full play to the sliding mechanism, which helps reduce the cutting force. The appropriate sliding cutting angle range of bush with large diameter is between 0°to 5°, and it comes to smaller when the diameter is larger. Diameter has significantly impaction on the cutting force, and the relation is Quadratic positive correlation. At last, the relation between moisture and cutting force is negative linear correlation.