Spiral gear is a key part used in mechanical transmission and power. It has high technical content, wide uses and large batch. The precision forming of the gear is numerically simulated and analyzed by using the finite element simulation software Defrom-3D.
- The parametric modeling of helical gear is carried out. The programming workload is reduced and the calculation accuracy is guaranteed by using the express tool of UG and the analytical method. The accuracy of symmetrical contour design is improved by using matrix transformation, and the calculation is reduced by using the operation of single tooth array. A relatively small part file is generated. The established equation can generate a new curve only by changing some parameters, with high reuse rate, Further improve the design efficiency.
- Through the numerical simulation analysis of closed die forging of helical gear, the process parameters of temperature and friction factor are selected for analysis. (1) Because the deformation resistance of aisi-4120 steel decreases with the increase of temperature, and the load decreases with the increase of billet temperature, it is easier to form; (2) When the friction factor is reduced, the load is also reduced, which can also reduce die wear and improve die life.
- The geometric parameters of helical gear are numerically simulated and analyzed, and the parameters of modulus, helix angle and taper are selected. (1) When the diameter of the dividing circle is the same, the larger the modulus is, the greater the load required for the forming of the helical gear is; (2) The change of helical angle of helical gear has little effect on its forming equivalent stress and forming load; (3) The larger the bevel angle of the helical gear, the more the metal axial filling and the less the radial filling, and the easier the helical gear is to form.
- Closed die forging of helical cylindrical gear adopts two kinds of blanks, one is the blank with boss and the other is the round bar blank. Compared with the blank with boss, the round bar blank is easy to process and saves materials. Through the numerical simulation analysis, it is found that the forming of the two billets is roughly the same. Due to the large strain value, the corresponding load is also slightly larger than that of the blank with boss. During its forming, when the blank is filled into the tooth cavity, the equivalent stress and equivalent effect at the tooth root become larger. In the final filling stage, the equivalent stress on the tooth top becomes larger.
- The closed die forging of spiral bevel gear is numerically simulated and analyzed, and its forming process is analyzed. During forming, when the blank is filled into the tooth cavity, the equivalent stress and equivalent effect at the tooth root become larger. In the final filling stage, the equivalent stress of tooth ejection becomes larger. The load required for closed die forging is 4500kN, and the metal at the gear teeth is prone to folding defects during forming.
- In view of the defects in the closed die forging of spiral bevel gear, the process is improved and formed by swing rolling. The metal at the upper end of the blank in the contact area deforms first and fills the tooth cavity, the metal gradually fills the tooth cavity from top to bottom along the helical surface of the tooth, and the tooth cavity at the lower end is completely filled at last. And the metal flow is evenly distributed without intersection, so as to avoid metal folding defects. The final load of swing rolling forming of spiral bevel gear is 550kn, which is 1 / 9 of the die forging forming load under the same conditions. Because the load required for swing rolling forming is small, the stress of the final forging and die is also small, and the demoulding is easier.
- After precision plastic forming of helical gear, the key problem of difficult demoulding of forgings is studied, and the radial bearing structure female die is designed. The tooth cavity can rotate freely along the axis of the helical gear. When the ejector rod applies axial upward stress to the forging, the forging also applies tangential stress to the die through the tooth spiral, so that the tooth cavity rotates along the spiral gear axis. The problem of synchronization between the axial upward movement of the forging and the rotation of the tooth cavity along the spiral gear axis is solved, and the forging is screwed out of the die.