The shearer gears are mostly heavy-duty gears, which require long service life and high reliability, especially to withstand the test of overload and impact. At present, almost all of the shearer gears produced by our company use 18Cr2Ni4WA steel. 18Cr2Ni4WA steel is a high-alloy carburized steel. After carburizing, the carbon content of the parts is high. After quenching, the core hardness is 32~38HRC, and the surface hardness is 58-62HRC. This design meets the requirements of heavy loads, but the subsequent finishing is a severe test.
The drawing shows a typical 18Cr2Ni4WA gear produced by our company. After carburizing and quenching, the hardness of the outer surface of the red painted surface is 58-62HRC, and the outer circle is concave in the spoke. The ordinary cylindrical grinding machine (M1350, MQ1650, etc.) cannot be processed at all.
18Cr2Ni4WA gear
Our company has long used Zigong Great Wall brand carbide blade YT726, which can meet the needs of external dimensions. With the increasingly fierce competition in coal mining equipment, the company proposed to build a "fine coal mining machine project", which puts higher requirements on the quality and production efficiency of shearer gears. Through research, the outer diameter of the outer circle has a finishing allowance of 0.4 to 0.5 mm before carburizing and quenching. The shearer gears are produced in small batches, using CBN tools, and still processed by the car grinding process. The tool selection is shown in Table 1. The cutting parameters and machine tool selection are shown in Table 2.
Table 1 
Table 2 
By applying CBN tools in shearer gear machining, the author summarizes the following points:
(1) The CBN tool can achieve the effect of grinding by car. Since the cutting depth is more than ten times larger than the grinding depth, the machining efficiency is high and the surface does not burn.
(2) When machining high alloys, the cutting speed of CBN tools is more than 5 times higher than that of hard alloy tools, and the cutting efficiency is increased by more than 3 times.
(3) The surface quality of the machine, the CBN tool has a good performance compared with the hard alloy knife.
(4) CBN tools are harder than hard alloy tools, and the service life is relatively long at the same purchase cost.
These are just some of the applications we have in the production of shearer gears. In the entire gear manufacturing process, we also use hobbing cutters, gear cutters, shaving cutters, internal and external turning tools, slotting knives, grinding grinding wheels and so on. The tool is the basis of our shearer gear manufacturing, and I am eager to design and manufacture the tool.
In terms of design, the designer cannot be “savingâ€, and the design is not simply mapping and imitation. The successful experience of tool companies at home and abroad is worth learning. However, this kind of learning should be based on analysis and understanding, grasp the principle of successful experience of others, and combine it with its own characteristics. This is feasible, it is the so-called "imitation Combine." Strengthen the design and development of composite tools, strengthen cooperation, and provide complete machining solutions that meet customer requirements.
In terms of manufacturing, we constantly upgrade the tool manufacturing technology and equipment level to improve the quality of the tool products from the inside out. Particular attention should be paid to the manufacturing level of the tool material heat treatment process.
In terms of services, some of our tool manufacturers rely too much on distributors to save costs and speed up capital turnover. In fact, many distributors know very little about tools. Therefore, there is a lack of communication and trust, which is not conducive to the trend of tool manufacturers to obtain customer technology development, which is not conducive to adjusting their product development strategies.
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