Experimental study on the technique of multi-arc gear cutting by carburizing


The position of the scraping hob before scraping is the position of the double-arc tooth-shaped transition arc, which does not participate in the work, and the precision requirement is low, but in order to improve the machining processability of the tooth profile before the scraping hob, Should be reserved. In order to reduce the burden of the carbide hob (hereinafter referred to as the scraping hob), the arc of the top of the hob is not left in the design. However, during the scraping process, whether the circular arc of the scraping hob participates in scraping depends on the amount of heat treatment deformation. As described in 1.3.1, the diameter of the root circle of the test gear increases to a different extent after heat treatment. The top of the scraping hob is involved in the scraping, which can be further explored in the future design of the hob before the scraping. The position of the scraping allowance is ensured by the residual tooth profile of the scraping hob.
The clamping of the scraping hob and the test gear requires that the large cutting force during the scraping process will cause large deformation and vibration of the machine tool. This deformation and vibration will affect the scraping accuracy of the gear, and in severe cases, the scraping hob will be chipped. Have serious consequences. Therefore, the scraping process requires a machine tool with a good rigidity. This scraping test uses the Y3180H gear hobbing machine. This hobbing machine is more common in China and has a certain representativeness. In order to ensure the accuracy of the scraping process, when installing the scraping hob, the radial runout of the two bosses should be no more than 0.01mm, and the center line of the hob center tooth should be facing the center line of the workbench. The tooling fixture for the scraping test gear should have good rigidity and high strength, and it is convenient to find the correct clamping clip. The gear of the large gear (disk shape) is relatively simple, and it is easy to meet the above requirements. The radial runout and the end face runout of the reference gear face are not more than 0.01mm; for the shaft gear, the chuck and the top effect are not ideal. The taper sleeve clamp or clamp can be used, and the radial runout of the reference gear shaft diameter of the normalizing gear is not more than 0.01mm. In the scraping test, the correction data of the scraping hob and the test gear should be retested during the second feeding. If there is a big change, you should re-install the installation and analyze the reasons for the change.
The orthogonal test of the scraping process This test takes the three elements of cutting (cutting speed v, the amount of cutting s, the feed amount t) as the test factors of the scraping process, determines the horizontal level and combines multiple combinations by orthogonal method for the scraping test. The test results were processed to find out the influence of test factors on each precision index. Finally, a better combination of test factors was recommended. The scraping process test was carried out on a Y3180H gear hobbing machine without any cutting fluid. According to the test, the up-milling vibration is relatively small, and the scraping effect is better.
Conclusion Through the research of scraping process, a new process field has been opened for the finishing of carburized and hardened hard-toothed double-arc gears. From the test results, using the conventional hobbing machine and high-quality carbide hob, select the appropriate cutting amount and fixture, carefully adjust the scraping process, the gear precision can reach 7 (GB/T15753-1995), The tooth surface roughness can be less than Ra3.2m. The accuracy achieved by the better combination of the three cutting elements recommended in this test can be called economic accuracy. Of course, if you have better scraping conditions, such as high-speed gear hobbing machines, higher quality carbide hobs, you can also make appropriate adjustments to the combination, the overall effect of scraping will be better.

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