1. 3D model of equidistant spiral bevel gear
According to the actual use and the characteristics of the gear, with reference to the relevant parameters of Gleason spiral bevel gear and relevant data, a pair of small module isometric spiral bevel gears are designed. The relevant geometric parameters are shown in the table.
| Parameter name | Big wheel | Small wheel |
| Rotation direction | Left | Right |
| Number of teeth | 16 | 23 |
| Axis intersection angle / ° | 90 | 90 |
| Pitch cone angle / ° | 34.824 | 55.176 |
| Modulus / mm | 0.905 | 0.905 |
| Mid point helix angle / ° | 30 | 30 |
| Tooth width / mm | 5 | 5 |
| Pressure angle / ° | 20 | 20 |
According to the parameter equations of spherical involute and equidistant conical helix, and the coordinate transformation, the tooth surface equation is derived. The discrete points of the tooth surface are calculated by programming in the software MATLAB, as shown in Figure 1; Then, the coordinates of discrete points are imported into the software UG for reverse modeling to close the tooth surface, as shown in Fig. 2 (a); Then, the top cone, root cone, front cone and back cone of the gear tooth are established, and then the accurate modeling of the equidistant spiral bevel gear small wheel is completed through the commands of trimming, stitching and array, so as to ensure the accuracy of the electrode processing and MIM simulation analysis of the subsequent small wheel. The model is shown in Fig. 2 (b).
2. Model test verification
Based on the three-dimensional model of equidistant spiral bevel gear, the electrode machining of gear is completed in the five axis linkage machining center, and the corresponding cavity is discharged on the precision spark machine, as shown in Fig. 3 (a). Referring to the finite element analysis results and the actual production and processing process of MIM parts, the MIM isometric spiral bevel gear mold is designed, and the metal powder injection molding of isometric spiral bevel gear is completed on the injection machine (using Fe ⁃ 8ni material). The product is shown in Figure 3 (b). It is verified that the small wheel of isometric spiral bevel gear can be demoulded by rotation, and MIM process can be used for mass production of isometric spiral bevel gear.
