The hard alloy blade has high hardness, great brittleness, poor thermal conductivity, and high thermal shrinkage. However, due to the high price of the diamond grinding wheel, it is difficult to repair after wear, so many factories still use the ordinary grinding wheels for cutting edge grinding. In the cutting edge grinding process, due to the high hardness of the hard alloy, the grinding grains of the ordinary grinding wheel is easy to be passivated. And the violent friction causes local high temperatures on the blade surface, forming the attached heating stress, easily causing thermal deformation and thermal crack, which directly affects the service life and processing quality of the tool. Therefore, necessary measures should be taken to prevent the emergence of blade grinding cracks. Through the processing practice, the following technological measures can be summarized to prevent or reduce the grinding crack effectively.
Methods/steps
Negative edge sharpening
The negative blade sharpening method is to grind a negative blade strip on the front or rear blade surface before sharpening the tool. Hard alloy is a hard and brittle material, and it is easy to vibrate and crack due to the vibration of the grinding wheel. At the same time, the thermal stress of the grinding zone may exceed the strength limit of the hard alloy and cause a thermal crack. The negative edge grinding method can improve the strength of the blade, enhance the vibration resistance of the blade, and the ability to bear impact load. And increase the heated area to prevent a large number of hot guide blades in grinding, so as to reduce or prevent cracks.
Soak grinding wheel with molybdenum disulfide
At room temperature, powdered molybdenum disulfide and absolute ethanol can be made into a mixed solution. In order to prevent ethanol from volatilizing, a new ordinary grinding wheel is then immersed in the mixed solution in a sealed container. After 14 hours, the wheel was taken out and naturally dried for 18-20 hours, so that the grinding wheel was completely dried. The inner voids of the grinding wheel treated above are filled with molybdenum disulfide, which can lubricate the grinding grains and make the grinding wheel discharge chips well and not easy to be blocked. The test shows that when grinding hard alloy blade with molybdenum disulfide wetted grinding wheel, the grinding is sharp, the grinding grain is not easy to passivate, the workpiece deformation is small, chip discharge is smooth, the shape of the grinding chip is basically ribbon-like, which can take away most of the grinding heat, thus improving the grinding effect and increasing the yield of the blade.
Reasonable selection of grinding dosage
If the friction force is too large in the grinding process, the grinding temperature will rise sharply and the blade will burst easily. Therefore, it is very important to select the proper grinding amount.Common reasonable grinding usage is: circumferential speed V =10 ~ 15m/min, feed f vertical =0.5 ~ 1.0m/min, f horizontal =0.01 ~ 0.02mm/ stroke.When hand grinding, longitudinal and transverse feed should not be too large.
Other process measures
The lack of rigidity of the tool pole, the instability of the tool clamping, and the runout of the machine tool spindle may cause the blade grinding crack. Therefore, the processing system composed of the machine tool, grinding wheel, fixture, and cutter should be rigid enough and the axial and radial runout of the grinding wheel should be controlled. There are many factors that cause a carbide tool to produce grinding crack. Only by selecting suitable grinding wheel and adopting reasonable grinding technology can crack generation be avoided effectively and the quality of grinding edge be improved.
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