When hobbing, the direction of motion of the hob teeth must be consistent with the direction of the teeth of the gear to be cut. However, due to the helical arrangement of the cutting teeth of the hob, the direction of the cutting teeth is not perpendicular to the hob axis.

Therefore, it is necessary to rotate the tool holder at a certain angle to coordinate with the tooth direction of the gear.

When hobbing, the rotation angle is the helix angle of the hob.

When hobbing helical gears, it is necessary to determine the size and direction of the turning angle based on the helical direction and helix angle of the helical gear.

1) Check if the calculation formula of the differential change gear is incorrect;

2) Is the number of teeth of the differential change gear consistent with the differential ratio;

3) Check if the keyways of the differential change gear and differential transmission shaft are loose or if the keys have fallen off;

4) If a differential mechanism is not used for rolling helical gears, the speed ratio of the selected cutting gear and variable speed gear should be recalculated to five decimal places.

5) Check whether the modulus, head number, left and right rotation direction, and helix angle of the hob meet the specified requirements;

6) Check if the installation of the hob and hob shaft is loose;

7) Check whether the processed gear blank is loose and tightened, and tighten the screws, nuts, and fixing devices accordingly;

8) When hobbing helical gears, please allow the machine to complete the entire process once and then check for errors.