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The spur gear is a typical mechanical part widely used. The traditional spur gear machining is a cutting process. It must be processed one by one for each tooth on a special machine. It takes a long processing time and it is difficult to increase productivity. At the same time, a large amount of material waste is caused, and a precision forging process scheme of the spur gear is proposed. Gear precision forging refers to the forging process in which the tooth surface of the forged gear member can be used without machining, or with only a small finishing allowance. In the precision forging process, the problem that the product is not qualified due to the difficulty of filling the corners of the material, whether the tooth cavity can be filled or even the forming force is too large, and the life of the die is lowered is more urgent in actual production. Based on this, the author proposes a process scheme of using a positive frictional action and a new type of flashing structure to precisely forge spur gears to ensure the filling of the tooth cavity, in order to optimize the machining of the spur gears. Practical applications provide a certain role.
1 Basic principle of active friction In metal plastic processing, there is always a certain contact friction between the blank and the sidewall of the die. If the direction of contact friction is artificially controlled, it is consistent with the flow direction of the metal, so that it is not only not It will prevent metal flow, but will promote the metal to fill the cavity better, and call this friction effect "active friction."
At present, the toothed piece precision forging process is taken as an example to illustrate the deformation mode after the end of the extrusion phase. The I zone and E are plastic deformation zones, and under the action of the punch, the metal of the zone is pushed to flow radially to the W zone. In a, as the punch is descending, the W zone and the V zone metal flow on the one hand in the zone, the metal of the zone I, in the direction of the tooth tip, and on the other hand, the upward extrusion, resulting in the lower corner metal of the tooth zone of the W zone. Hard to fill. Because the metal of the VI area forms a single drum shape under the friction of the convex end surface, the flash edge is formed prematurely to make the upper tooth cavity not full.
In b, after the punching process is finished, the punches push the movable die to move downwards, and the direction of the frictional force on the contact surface of the die is consistent with the direction of metal flow, which plays a beneficial role in the deformation. Therefore, the W zone When the V-zone metal flows toward the top of the tooth, it moves downward, ensuring the filling of the lower-tooth cavity. The metal in the VI area is similar to the upsetting of the cylinder, but the deformation height is always the same due to the same amount of movement of the convex and concave molds, which improves the friction condition of the contact surface, so that the deformation tends to be uniform (X5X45 is uniform, which is favorable for the upper tooth cavity to be filled.
2 simulate the principle of action to design the mold. Shown is a tractor reduction gear part of a factory, the number of teeth Z=15, modulus m=3.5. Industrial pure lead is used as the test material, and the spur gear is made on the solid blank 46mmX 600kN hydraulic universal testing machine.
4 Conclusion The key to the success or failure of art is the complete filling of the tooth cavity. Based on the active friction mechanism, this paper proposes a scheme of precision forging spur gears using movable die. Simulation experiments with industrial pure lead have shown that complete filling of the tooth cavity in this solution is guaranteed.
(3) Reducing the precision forging deformation is a guarantee for improving the life of the mold. Under the premise of ensuring that the tooth cavity is completely filled, how to reduce the deformation force is the next step to study, which provides a reliable theoretical and experimental basis for the practical application of the spur gear precision forging process.
