Analysis of hard tooth layer multi-shaving technique
Wenzhou Yuanda Electronic Technology Co., Ltd , https://www.wzyddz.com
Overview In general, the common methods for tooth profile machining of 6 to 7 hardened gears are: (1) rolling, shaving, heat, and enthalpy. (2) Rolling, heat, and grinding. (3) Rolling, heat, and scraping.
Although the "rolling and grinding" process can better ensure the processing precision of the gear, the grinding gear has a large investment and a low production efficiency. The "rolling and scraping" process has higher requirements on the rigidity of the hobbing machine. Generally, the hobbing machine is difficult to meet the requirements. At the same time, the accuracy index of the individual gears is difficult to guarantee. The “rolling, shaving, smashing†process equipment has simple requirements, high production efficiency, and the gear precision before quenching can be well guaranteed, and is usually adopted. However, due to the influence of heat treatment, the large quenching deformation causes the original gear precision to be destroyed, and the general caries process cannot eliminate this effect, which causes the gear to generate a large noise when meshing. In the past, our factory encountered this situation when producing C6240 bedside gears. Later, we used the “double shaving process†to solve this problem better.
Process parameters and requirements The so-called "double shaving process" is to add a hard shaving process based on the ordinary "rolling, shaving, heat, smashing" process, namely: "rolling, shaving, hot, hard shaving, smashing". In general, shaving is only suitable for finishing before gear quenching. However, if the gear with a certain hardness on the tooth surface after quenching is shaved, it puts some special requirements on the tool, tooling and process parameters, especially It is a tool. In general, to ensure good shaving and high tool durability, the difference in hardness between the tool and the workpiece is greater than HRC20. The hardness of the headboard gear produced by our factory is HRC45~48, so we have ordered a high cobalt steel M42 shaving cutter. The hardness of the tool is HRC70 ~ 72, good wear resistance and long life. Since the shaving cutter is to be hard-cut, the rigidity and vibration resistance of the machine tool and the tooling are required to be high. Our factory selected Y4232A horizontal shaving machine, and re-made a special shaving core rod. The length of the core rod is short, the diameter and the positioning step surface are large, and the workpiece is all pressed by the nut. The headboard gears produced by our factory are all 7-level precision, the modulus is 2.25~3.5mm, and the outer diameter is 60~220mm. According to the processing characteristics of hard shaving and the experience of repeated exploration, the selected process parameters are as follows: hard razor The outer diameter is 240mm, the helix angle is 151, the right hand rotation, the accuracy grade is A grade, the gear hard shaving margin (common normal line) is 0.02 ~ 0.03, the shaving cutter speed is 111r / min, the axial feed is 2 ~ 2.8 Reciprocating stroke / min, radial feed amount is 0.005 ~ 0.01mm / reciprocating stroke. Since the hard razor is brittle, the type II shaving hob must be used for hobbing, so that the gear teeth of the machined gear are chamfered and the roots are undercut, so that the shaving angle of the shaving cutter is not crushed by the cutting. damage. In addition, hard shaving is a hard-to-hard cutting, and the tool is easily blunt, so the cooling must be sufficient, and the thinner No. 10 mechanical oil can be used for cooling. The tool should be re-grinded regularly. It is better to find the law of tooth-shaped heat treatment deformation during re-grinding, and to modify the tool to reduce the noise during gear meshing.
Precautions (1) The shaving cutter should be lightly attached and detached. It is strictly forbidden to hit the tooth with a heavy object.
(2) The workpiece clamping must be firm, and the two thimbles should be tight and stable.
(3) Before shaving, be sure to remove any debris, bumps, and so on.
(4) The caries process can be omitted depending on the situation. If the caries are needed, the amount of honing should be minimized.
(5) Minimize the amount of deformation of the tooth quenching.
After a year of research and exploration of the “double shaving processâ€, we believe that the method is simple, the process cost is low, the production efficiency is high, and the effect is obvious. The test proves that after the "double-shaved" gear is mounted on the machine tool, the bedside box noise is reduced by about 325dB, and the noise is small and the sound is pleasant. It proves that the process has good feasibility and practicability.