As shown in the figure, the tool shifting length of gear hobbing hob is calculated according to the following formula:
Where:
Ls — tool shifting length of gear hobbing hob;
L3 — effective length of gear hob;
Le — cutting edge length of gear hobbing hob (minimum length of hob);
LPO – gear tooth profile development length.
After machining one or several gears, the gear hobbing hob moves a distance relative to the gear along its axial direction to ensure the uniform wear of the gear hobbing hob teeth – called tool channeling. In order to reduce the tool cost of gear hobbing and the auxiliary time of tool change, the tool shifting length of gear hobbing hob should be as long as possible.
The tool shifting length of the gear hobbing hob shall be compatible with the machine tool used. If the length of the tool shifting part of the gear hobbing hob is greater than the tool shifting length that the machine tool can perform, it is a waste and will increase the cost of the tool.