Development and application of large modulus trimming comb cutter

Our company's MAG comb machine (SH1200) is one of the few gear finishing equipments in the world with a diameter of more than 10m. The tool for machining gears is a comb cutter. The comb cutter is a kind of cutter which is used to process straight teeth, helical teeth and herringbone gears according to the principle of meshing between the rack and the gear, and is also called a rack knife. Straight-toothed and slant-toothed combs are used to machine spur, helical and herringbone gears from M1 to M70mm or larger. They can also be used to machine herringbone gears with small sipe and no empty sipe. Depending on the comb holder, the Marg comb cutter is designed. The Marg comb cutter has no front angle when it is manufactured. After being mounted on the machine, it relies on the tilt of the tool holder to obtain a working rake angle of 6°30'. According to the nature of the processing, the comb cutter is divided into three types: a coarse-cut comb cutter, a semi-fine comb cutter and a fine-cut comb cutter. It can also be designed into various forms such as a pre-grinding comb and a root comb.

Test analysis

Workpiece name: f5.2mm×48m dryer large ring gear, material is ZG42CrMo, normal modulus Mn=50, number of teeth z=144, pressure angle αn=20°, β=0° (straight tooth), tooth top repair Shape E=0.94, shape height Dh=31.42mm, root radius r=19.5mm, tooth thickness tolerance Ds=-3.526mm, accuracy grade AGMA10, tooth surface roughness value Ra=3.2mm, design required heat treatment Hardness: 280 ~ 320HBW.

2. Design analysis

The large ring gear of f5.2mm×48m dryer is the modified gear of Mn50. The design and manufacture of Mn50 super large modulus trimming comb cutter is still blank in China, so the design and manufacture of comb cutter need innovation. Innovative points: 1 It is necessary to study the relationship between the parameter design of the toothed shape modification part of the combing cutter and the tooth shape of the machined gear to ensure the tooth profile accuracy of the machined gear. 2 Study the transition relationship between the tooth top arc and the tooth shape of the root comb comb before combing. If the comb top tooth enters the knife, the bending moment generated by the cutting will increase and the cutting resistance will increase sharply. The cutting is not smooth, and the vibration phenomenon occurs. The lighter may cause corrugations on the tooth surface, and the surface quality is poor. In severe cases, the file may be caused by a sickle or even a knife.

3. Tool design form

The tooth size of the Mn50 gear is not smaller than the small and medium modulus, it is an oversized specification, and the gear requires trimming of the tooth profile. According to the design principle of the comb cutter, combined with the tooth shape parameter requirement of the φ5.2mm×48m dryer gear of Japan Kawasaki Co., Ltd., a root comb comb cutter (see Fig. 1, Fig. 2) was designed; a comb comb cutter , as shown in Figure 3 and Figure 4. The material of the comb cutter is W6Mo5Cr4V2Al, and the surface of the cutter is coated with TiAlN. After the surface of the tool is coated with TiAlN, the wear resistance of the tool can be significantly improved, and the surface quality of the machined part can be improved.

Figure 4

4. Tool application

Before the comb tooth, the tooth ring thickness of the large ring gear is 2mm, and the tooth root is 1.0~1.2mm. First, the root depth is processed to the design size by the root combing knife, and then the combing tooth is used to comb the teeth. In the process of combing the teeth, when the tooth thickness is still 0.2mm, it is found that the circular arc of the comb-toothed cutter has participated in the knife, which increases the bending moment generated by the cutting, and the cutting resistance increases sharply, resulting in unstable cutting. There is vibration. Causes the tooth surface to be corrugated, the surface quality is poor, and the sickle phenomenon occurs.

Through the analysis of the tool design parameters, it is found that the root of the tooth of the root comb is too large, which is not conducive to the combing teeth.

It can be seen from the comparison of the tooth shape of the root comb and the comb comb (see Fig. 5) that the arcs of the tops of the two comb teeth do not coincide and there is a gap. After the root comb cutter is processed, the circular arc of the comb tooth cutter participates in the cutting, which is not conducive to comb teeth. Therefore, there is room for improvement in the root combing cutter, which needs to be improved to ensure that the comb-toothed tooth top arc does not participate in cutting. After research and analysis, the combing cutter is improved, the cutting part of the tooth top is preserved, and the flank cutting edge is designed according to the shape of the root cutting knife, and a new root carving comb cutter is added (see Fig. 6).

The cutting process of the root-cutting comb cutter modified with the comb-toothed cutter is stable, no abnormal situation occurs, and the arc comb of the gear root is smooth.

Subsequently, the combing cutter is used to comb the teeth, the combing process is smooth, and there is no vibrating knife phenomenon, and the processing of the large ring gear is satisfactorily completed. The tooth profile of the large ring gear has passed the test, which proves that the tooth shape parameter design of the comb tooth cutter is correct and reasonable, especially the tooth profile modification part has been carefully verified, and the result fully meets the product design requirements (see Figure 7).

5 Conclusion

The Mn50 shape-trimming comb cutter developed by our company successfully completed the comb tooth processing of the f5.2mm×48m dryer gear, and the machining precision fully meets the product design requirements. At present, the maximum modulus of the domestic gear hob reaches Mn45, and the Mn50 super large modulus trimming comb cutter fills the gap of the domestic super large modulus gear cutter. The successful development of Mn50 super large modulus trimming comb cutter has enabled our company to have unique technical processing capability in the field of super large modulus gear processing. It is the best choice for solving the processing of super large modulus gears, and has a higher market for further development of the company's products. Strategic and economic significance.

references:

[1] Zhang Lei, He Lian Xu Yang, Huang Xinhua, et al. Research on the modification technology of large gear cutters[J]. Mining Machinery, 2014(12): 119-123.

[2]Jiang Dongmei. Design and manufacture of three kinds of single-head helical gear combs[J]. Equipment Manufacturing Technology, 2008(3): 123-125.

[3] Hu Liangbin, Li Biwen. Research on Adaptive Design Principle and CAD Method of Shaped Comb Knife[J]. Equipment Manufacturing Technology, 2009(10): 27-29.

[4] Ji Jiangang, Zhang Lei, Huang Xinhua, Li Tiefeng. Innovating Technology and Evaluation Method of Involute Cylindrical Gear[J]. Mechanical Transmission, 2014(4): 172-176.

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