Development of scraping machining of hard tooth surface of spiral bevel gear in China

Since 1982, Hanjiang tool factory and Taiyuan Heavy Machinery Factory have cooperated to study 18 ‘single edge precision cutting cemented carbide milling cutter head. The trial cutting of gears was carried out in 1984 and satisfactory results were obtained. In 1985, more than 100 pairs of gears were manufactured by this process. After installation, the industrial rolling test was carried out in Chengdu 65 plant. The quality of the rolled alloy steel pipe is completely qualified, the meshing of spiral bevel gears is normal, and there is basically no wear. The cutting tool is made of ultra-fine grain cemented carbide produced by Shaanxi steel works. The blade inclination is – 16 °, the rake angle of the top edge is 0 °, and the radial rake angle is – 15 °. Two internal and external cutter heads are installed on the cutter head, 180 ° apart. The hardness of spiral bevel gear is HRC58-62, and the machining accuracy reaches grade 8-7-7dc (jb180-60).

Almost at the same time, Liaoning University of engineering and technology and Shijiazhuang Coal Mining machinery factory set up a scraping research group to develop hobs, bevel gear planers and spiral bevel gear milling cutter heads, and put forward the “oblique angle straight line forming method”. They used national y225 and y228 gear milling machines, tested their performance and made vibration tests. The test shows that most of the existing intact machine tools can be used for scraping as long as the cutting parameters are properly selected; They adopted a new scraping cutter head, which uses cemented carbide as the cutting head material and adopts oblique cutting edge to overcome the disadvantage of poor impact resistance of cemented carbide material; At the same time, in view of the change of blade shape and position caused by oblique cutting, the cutting edge of the tool is designed as a straight edge with a certain edge inclination. The hyperbolic production formed by its rotation is tangent to the conical production surface of the high-speed steel cutter head in semi finish milling at the center of the tooth surface contact area, so as to ensure the consistency of the pressure angle at the center of the tooth surface contact area; The different inclination angles of the inner and outer cutter teeth are selected to compensate the forming surface error and ensure the length of the contact area. This shaping method makes the manufacturing and testing of cutting edges very convenient, and is convenient to be popularized and used in small and medium-sized enterprises. This technology has solved the problem of hard tooth surface machining of spiral bevel gear and achieved obvious economic benefits. The geometric parameters of the tool selected by them are the forward angle of the side edge axis – 10 ° ~ – 15 °, the radial forward angle – 15 ° ~ – 25 °, the machining accuracy of the tooth surface can reach grade 6-7 (jb179-60), and the roughness is ra1-2um.

In order to meet the needs of hard tooth surface machining, Tianjin No. 1 machine tool factory has developed y2250a and y2275 spiral bevel gear milling machines. Y2250a spiral bevel gear milling machine tool is improved on No. 116 machine tool in the United States. It is suitable for mass processing of semi hobbing gears of medium-sized and truck axles. Y2250a and y2275 gear milling machines are superior to previous models in terms of rigidity, cutting accuracy and productivity.

At present, the scraping technology of hard tooth surface of spiral bevel gear, as an effective means to eliminate heat treatment deformation, has been more and more widely used.