Design And Experimental Study On Coal And Rock Cutting Tester

Coal and rock cutting was an important part of the mechanized mining.The reliability of the whole coal mining machine and productivity will be directly affected by the coal shearer drum and roadheader cutting head and cutting performance.Under an engineering background of mining machinery coal and rock cutting, design and experimental study on coal and rock cutting tester were studied in this paper. On the basis of designing tester mechanical systems, hydraulic systems, measurement and control systems, under random variation of the cutting force, the stability analysis of cylinder speed based on the AMESim simulation and experiment were studied; coal and rock cutting experiments were conducted on the tester, the magnitude of cutting force, specific energy, cutting debris particle size fractionation and cutting load spectrum analysis under different cutting speed and depth were researched. The main conclusions of this paper were listed as follows:(1).In the design of mechanical systems, the cutting depth could be adjusted in the range of 0-20 mm, and cutting space 0-200 mm. In the design of hydraulic system, the speed of the hydraulic cylinder was unlikely affected by the cutting force under random variation and precise speed control in the range 0-0.3m/s was achieved. In the design of measurement and control systems, on the basis of achieving precise control of the cutting speed, the three-dimensional cutting forces and cylinder displacement(velocity) were measured, the pressure of the hydraulic system, accumulator outlet and the clamping cylinder of moving beam were monitored.(2).Based on AMESim, the simulation analysis of hydraulic system were researched, when the loading was null, sinusoidal and random variation, under the same system pressure, the speed of the hydraulic cylinder was stable. Under the same system pressure, the speed of hydraulic cylinder was increased with the opening of proportional valve. When the loading was sinusoidal variation, and oil source of the system was pump, the cylinder speed, system pressure and outlet pressure of accumulator were relatively stable.When oil source of system were the accumulator and pump, also,the proportional valve opening degree was smaller, the system pressure and the outlet pressure of accumulator were decreased with time, however, the system could provide a flow rate which was greater than the theoretical flow of proportional valve, and the cylinder speed was stable; when the proportional valve opening degree was larger, the lower system pressure was insufficient to provide adequate flow of accumulator, the hydraulic cylinder speed was decreased with time.(3).Under no-loading and cutting experiment condition on the tester, the hydraulic system was researched,and the conclusions were as follows: in the hydraulic system of coal and rock cutting tester, the hydraulic cylinder speed could be precisely controlled through a given voltage signal on proportional valve; the simulation and experimental results were showed the speed of the hydraulic cylinder was stable when the cutting force under random variation, the dynamic response of the entire hydraulic system was better and able to meet the requirements of coal rock cutting test.(4).Under the condition of cutting depth 5mm, cutting angle 45°and cutting space 100 mm,the cutting experiments of different cutting speeds were conducted, the three-dimensional mean cutting forces were changed unsignificantly with cutting speeds; the total mass of debris were increased with the cutting speed,also, the quality of each block range at the proportion of the total mass debris was basically same; the cutting specific energy were increased at first and then decreased with cutting speeds, under the lowest cutting energy rate, there was a cutting speed v = 0.158m/s, which could produce optimum cutting conditions and economic benefits; in the analysis of cutting force spectrum, large amplitude signals of cutting forces were in the low frequency 0-10 Hz, which focused most of the energy. There has been the peak point frequency compared to the surrounding area at some point, which indicated the existence of quasi-periodic component of the cutting force signal.(5).Under the condition of cutting speed 0.158m/s, cutting angle 45°and cutting space 100 mm,the cutting experiments of different cutting depths were conducted, the cutting force and the normal force were increased linearly with cutting depth; when the cutting depth were 5, 10, 15 and 20 mm, the proportion of cutting debris block rate was greater than 25 mm were: 21.8%, 50.8%, 63.4% and 64.75%, which showed that when increased cutting depth could increase the rate of the cutting block debris significantly; in the analysis of cutting force spectrum, the maximum cutting force was increased with the cutting depth at the frequency of 0Hz, the destruction cutting force values were increased with cutting depth, which was related to the reason of producing larger pieces of debris when cutting depth was larger. The specific energy had a higher exponential relationship with the index of particle size distribution, the index could be used to estimate the efficiency.of coal and rock cutting.