The error caused by the change of radial distance between the gear hob and the axis of the processed cylindrical gear is called radial machining error. The possible factors causing the error are: the radial positioning error of gear blank in gear hobbing, the periodic change of gear blank axis or hob axis, the radial runout of hob, etc.
1) Geometric eccentricity caused by radial positioning error of gear blank. Geometric eccentricity refers to the eccentricity or non coincidence between the rotation axis during gear hobbing and the rotation center when the gear is used.
2) Installation error of gear hob. When gear hobbing machining cylindrical gear, the installation error of hob refers to the offset between the actual installation position and the theoretical installation position caused by various factors in the installation process of gear hob. There are three main installation errors of hobs: the first is the radial runout of gear hobs, which refers to the deviation of gear hob axis from the theoretical hob installation axis after installing hobs or when hobs are in cutting motion; The second is the axial movement of the hob, which means that the hob has a variable momentum along the axial direction compared with the theoretical installation position of the gear hob; The third is the error of the intersection angle of the gear hob installation axis, which means that the actual gear hob axis is inclined by an angle compared with the ideal hob axis.