1.Edge of tooth surface
Main cause
The profile error of hob is too large or the tooth splitting is powerless. The instantaneous speed changes greatly. There are four kinds of workpiece defects
(1) After the sharpening of the hob edge, the tooth equivalency is poor
(2) Large axial movement of hob
(3) Large radial runout of hob
(4) Blunt for hob
Resolvent
Main methods: focus on the grinding quality of the hob, the installation accuracy of the hob and the geometric accuracy of the machine tool spindle:
(1) Control the grinding quality of hob
(2) Ensure the installation accuracy of the hob, and at the same time, do not knock when installing the hob; the end face of the washer shall be flat; the end face of the nut shall be vertical; the inside of the taper hole shall be clean; after the bracket is installed, no clearance shall be left
(3) Recheck the rotation accuracy of the machine tool spindle, and repair and adjust the hob spindle bearing, especially the thrust washer
（4） Replace with a new knife
2.Asymmetric tooth shape
Main cause
1) Incorrect installation of hob
2) The radial error of the front edge surface is large after the grinding of the hob edge
3) The error of helix angle or lead is large after the grinding of the hob edge
4) The installation angle error of hob is too large
Resolvent
1) Incorrect installation of hob
2) The radial error of the front edge surface is large after the grinding of the hob edge
3) The error of helix angle or lead is large after the grinding of the hob edge
4) The installation angle error of hob is too large
3.Incorrect tooth angle
Main cause
1) The error of hob tooth angle is too large
2) The radial error of the front edge surface is large after the grinding of the hob edge
3) The installation angle error of hob is large
Resolvent
1) Reasonable selection of hob accuracy
2) Control the grinding quality of hob
3) Readjust the installation angle of hob
4.Periodic error of tooth profile
Main cause
1) After the hob is installed, the radial runout or axial movement is large
2) Uneven rotation of machine tool table
3) Installation eccentricity or tooth surface collision of cross wheel or split exchange gear
4) Tool holder slide plate is loose
5) Vibration caused by unreasonable clamping of workpiece
Resolvent
1) Control the installation accuracy of hob
2) Check the axial movement of the indexing worm of the machine tool table, and adjust and repair it
3) Check the installation and operation of the span wheel and the split exchange gear
4) Adjust the stopper iron of the tool slide plate
5) The correct scheme of reasonable selection of workpiece clamping