Traditionalmachining is based on the principle of “imaginary flat top gear”. At present, the basic idea of the processing method of spiral at home and abroad is also the principle of “imaginary flat top gear”, which is only based on the principle of continuous improvement and correction. As shown in the figure, suppose a flat top gear is engaged with the gear to be processed for transmission. The assumed flat top gear is a bevel gear with a top cone angle of 90 degrees and a pure rolling relationship between the pitch cone and the pitch cone of the gear to be machined. In the process of gear cutting, it is assumed that the flat top gear will engage with the gear to be processed without clearance. The movement track of the cutter tooth on the milling cutter is the tooth surface of the flat top gear. Then the cutter tooth is cut on the blank to generate the spiral bevel gear tooth surface according to the meshing transmission relationship between the flat top gear and the gear to be processed.
In the process of gear cutting, since the imaginary flat top gear and the gear to be machined are conjugate transmission relations, the pitch cone surface of the imaginary gear and the pitch cone surface of the gear to be machined must ensure the pure rolling relationship; the root cone and tooth slot of the gear to be machined are cut and generated by the tooth top plane of the imaginary gear in the transmission process, so the rotation plane of the imaginary gear must be the same as that of the gear to be machined The root cone is tangent. Then the rotation axis of the gear to be processed and the rotation axis of the imaginary flat top gear form an angle of “90 ° + root cone angle”. In order to ensure the above relationship, the tooth angle of the blade must be corrected. At the same time, because the pressure angle of the tooth in the direction of the tooth height is not equal, the gear cutting machine needs to be adjusted.
Based on the theory of spiral bevel gear cutting, the key structure of traditional spiral bevel gear cutting machine is analyzed. As shown in the figure, the movement of the milling cutter head is jointly controlled by the drum wheel, eccentric wheel and cutter tilt mechanism of the shaking table, so that the spatial movement track of the cutter teeth in the processing process is the surface of the teeth of the imaginary flat top gear, so as to ensure the pure rolling relationship with the bevel gear to be processed to cut the tooth surface of the spiral bevel gear.
For the processing of spiral bevel gears with different directions, it is mainly determined by adjusting the relative position of the bevel gear to be processed and the rotating axis of the cradle in the vertical Z direction. The spindle of the blank can move up and down the vertical track on the side of the workpiece box to adjust the vertical wheel position. When the axis of the main shaft of the gear blank intersects the axis of the cradle, the scale value of the vertical wheel position is 0. When machining the left-hand spiral bevel gear, the main shaft of the gear blank should move downward relative to the axis of the shaking table, and the vertical gear position scale value is negative; when machining the right-hand spiral bevel gear, it is the opposite. The modification of bevel gear tooth thickness and cutting depth can be adjusted by controlling the workpiece box to move with the rotating plate in the horizontal direction. When the workpiece box moves forward, the tooth thickness and depth of the processed spiral bevel gear become smaller and larger; otherwise, the tooth thickness and depth become smaller. The installation angle of the gear to be processed can be adjusted by controlling the rotation of the workpiece box on the rotating plate. The initial machining position must ensure that the angle between the axis of the gear blank and the axis of the machine tool cradle is “90 ° + root cone angle”. In the process of tooth cutting, the feed and return movement is realized by controlling the rotary movement of the workpiece box on the rotary plate and its forward and backward movement along with the rotary plate on the saddle of the bed.