Cutting machine system. Cutting spray gun 2, 4. High pressure hose connection 3. Abrasive tank 5. Water tank 6. Motor 7. High pressure water pump (2) Design technical parameters Working pressure / MPa35 motor power / kW6 pump flow / Lmin-14 nozzle diameter / mm0.6 Abrasive type garnet abrasive grain size / mesh 120 abrasive flow rate / kgmin-12.53 cutting speed / mmmin-150100 abrasive tank volume / L50 tank volume / L70 foreword based on the characteristics of water jet "cold" cutting, using high pressure water jet technology to cut coal mine underground high Metal equipment in a gas environment is a safer way to cut. Adding abrasive to pure water and cutting it with pre-mixing can greatly improve the cutting effect. Due to the environment caused by the coal mine underground and the overall workload of cutting, the metal cutting degree of the downhole is required to be low, and the requirements for the uniformity of the slit are not high, and the requirements are simple and easy to operate. In addition, since the water jet cutting does not need to directly contact the cutting workpiece, the reaction force is small, and the construction personnel can be well protected. Therefore, it has important practical significance to develop a portable coal mine water jet cutting machine.
1 The main design parameters of the cutting machine are as shown. The portable cutting machine designed in this paper is mainly composed of water tank, explosion-proof motor, high-pressure water pump, high-pressure abrasive tank and high-pressure spray gun. The working principle and operation flow are as follows: Firstly, the high-pressure water pump is increased to a pressure of 35 MPa, and the high-pressure water is divided into two channels through a high-pressure water distribution pipeline: a balanced water passage and an ejector water passage. The abrasive in the high-pressure abrasive tank is fluidized under the action of high-pressure water, and flows downward to the mixing chamber located under the abrasive tank; the ejector water channel mixes the abrasive and the high-pressure water uniformly, and is output from the other side of the mixing chamber, and the balanced waterway The high-pressure water merges to form a high-pressure abrasive slurry and is sent to the spray gun; the high-pressure abrasive slurry is sprayed through the nozzle orifice (quasi-=0.6 mm) to form a high-speed abrasive water jet with extremely high energy density to complete the cutting operation.
2 Cutting test and analysis After the prototype of the portable coal mine water jet cutting machine was completed, the cutting performance and cutting effect of the cutting machine were tested. The test scheme is as follows: Select the four cutting parameters with large influence to test separately; the four main process parameters are the driving pressure P of the system, the supply flow rate of the abrasive Q, the vertical distance between the nozzle and the workpiece (target distance) b and water jet cutting Nozzle moving speed (cutting speed) v; only change the value of each parameter variable in each test, record its influence on the cutting depth and cutting efficiency, compare and analyze the data obtained by the experiment, summarize the optimal working parameters, and propose improvement measures.
The curve of the maximum depth with the driving pressure for one cut. It can be known from the cutting principle that the larger the driving pressure, the greater the damage of the jet to the material being cut due to the increase of the speed and momentum of the abrasive jet, and the cutting ability is also improved. The driving pressure of the cutting depth randomizer shown in the figure increases linearly. In the cutting machine system, the driving pressure is a performance index with high energy consumption and maximum cost. In order to ensure that the cutting machine can work economically, stably and efficiently, the appropriate driving pressure must be selected. Therefore, the selection of the driving pressure should consider other parameters. And economics and stability, not the bigger the better. For this cutting machine system, after a lot of experimental research and parameter configuration calculation, the driving pressure has better economic stability at 35MPa.
The influence of driving pressure is the curve of the maximum depth of one cutting with the abrasive flow rate. The influence of the abrasive flow rate on the maximum depth of the secondary cutting increases first and then decreases. The maximum abrasive flow rate is 3.5 kg/min. If the abrasive flow rate If it is too small, the cutting energy will be reduced and the cutting performance will be degraded. If the abrasive flow rate is too large, the nozzle will be blocked, the abrasive exit speed will be reduced, and the abrasive waste and environmental pollution will easily occur. Therefore, the abrasive flow rate is selected. Hours, should not be too big or too small.
The effect of the abrasive flow rate is the effect of the cutting target distance on the maximum depth of one cut.
The target distance is defined as the vertical distance from the exit end of the cutter nozzle to the cut surface of the material being cut. The graph shows that the influence of the cutting target distance on the cutting depth increases first and then decreases. When the cutting target distance is 10 mm, the depth of one cutting has the maximum value.
If the target distance is large, the abrasive jet velocity will reach the maximum and the cutting surface has begun to drop rapidly. If the target distance is too small, the abrasive cannot be accelerated to the maximum value, so that the cutting can not achieve the best application effect.
Curves for cutting depth and efficiency as a function of cutting speed. Cutting efficiency is defined as the product of the maximum depth of the secondary cut and the cutting speed. The higher the cutting speed, the lower the maximum depth of the secondary cutting, and the cutting efficiency first increases and then decreases. When the cutting speed is maintained at 80 mm/min, the cutting efficiency reaches a maximum. Because the cutting speed will increase, the cutting will not be sufficient, thus affecting the maximum depth of cutting; if the cutting speed is too low, it will cause waste of cutting energy, affecting the cutting progress and efficiency. Therefore, the choice of cutting speed should be based on the cutting efficiency, and choose the appropriate cutting speed.
3 Conclusion Portable front-mixed abrasive water jet cutting machine cutting metal material is a cold cutting method. Due to the existence of water, it has high safety in the high gas environment of coal mine, and its cutting ability and cutting efficiency have outstanding advantages, so the cutting The application of the system has important practical significance for improving the safety of coal production; the portable water jet cutting machine is easy to operate, reliable in performance and high in work efficiency. It greatly simplifies the cutting task in coal mines and achieves efficient and safe production. During the installation and commissioning process, there is no abnormal operation and other emergencies, and normal and efficient operation is realized. The design parameters of the cutting system are selected to meet the requirements of safety performance, and the design principle is accurate and reliable. The designed and produced portable water jet cutting The system has been tested and summarized, and its working parameters are determined: the driving pressure is p=35MPa, the abrasive supply flow rate is Q=3.5kg/min, the cutting distance is b=10mm, and the cutting speed is v=80mm/min. In this working parameter The cutting system has high system stability and economic benefits.
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