Improvement of forged gear blank production line

Some situations and solutions encountered in the forged gear blank production line are described below.

(1) During parting, the forged gear blank can not always stay in the lower die, which is convenient for robot picking. This kind of press generally adopts hydraulic feeding and jacking structure, but the hydraulic feeding and striking mechanism has the characteristics of hydraulic “hysteresis”, resulting in that during parting, the forged gear blank will not be completely separated from the upper die until the slider returns to a certain height, so that the forged gear blank can not be guaranteed to remain in the lower die all the time for the normal picking of the manipulator. Once this problem occurs, There will be one of the following two situations: ① the robot will be empty, resulting in the shutdown of the production line; ② The robot clamping deviation causes the precision forging of serial teeth, and the forged gear blank is directly scrapped.

Therefore, in practice, it is necessary to design an elastic energy storage upper jacking mechanism to ensure that the forged gear blank is always left in the lower die when the slider returns in the forging process, so as to facilitate the robot to take materials. Generally, nitrogen spring or disc spring elastic energy storage jacking device is used.

(2) The forged gear blank is eccentric. During the forging of the gear, due to the anisotropy of materials, the difference of lubrication conditions and the low guiding rigidity of the die, the unilateral eccentric displacement of the forged gear blank reaches 0.4mm ~ 0.5mm. There is a risk of insufficient machining allowance on the machined surface of the forged gear blank. Through analysis, it is found that the effective lead of the guiding device is too small to fully play the guiding role. Later, the lead size of the guide device was readjusted to ensure that the effective lead of the blank before compression deformation was greater than 5mm. Through this improvement, the unilateral eccentric displacement of the forged gear blank was completely controlled within 0.15mm.

(3) During the forging process, the tooth die of pre forging and final forging is loose and the position of the corresponding tooth rotates. The equipment vibration during forging will lead to the loosening of the die in the production process, resulting in the axial rotation offset of the corresponding tooth position of the debugged pre forging and final forging tooth die, resulting in the tooth channeling of the pre forged gear blank and the scrapping of the fine forging. After analysis and improvement, the positioning key is added on the die base to effectively prevent the die from rotating after loosening.

(4) Low die life and frequent die change. At present, the service life of gear hot forging dies is generally not high. For example, the service life of dies in this production line is about 10000 pieces. Through the cooperative test with colleges and universities, PVD (physical vapor deposition technology) coating treatment is carried out on the mold surface (see Figure). The service life of the mold has been increased to 28000 ~ 30000 pieces. The application of this technology has greatly extended the service life of the mold and improved the efficiency of the production line. This technology has entered the stage of batch application in our company.

(5) The process of die changing and debugging is complex. Each time a new die is replaced, it is necessary to repeatedly adjust the position of the corresponding teeth of the pre forging and final forging dies. The debugging time is generally 120min. After improvement, the machining benchmark and keyway are designed on the pre forging and final forging die. After direct die installation, it can effectively ensure the complete alignment of the tooth profile of the pre forging die and the final forging die, and the die change time is completely controlled within 40min, so as to truly realize rapid die change.

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