Hobbing

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Gear planing is a variant of planing for gears or other toothing.

In gear planing, the tooth gaps are produced by means of oscillating stroke movements of the tool . The tool used is the so-called planing comb (also known as a cutting comb ), the appearance of which is similar to a segment of a rack . However, the teeth are relief-ground to ensure sufficient clearance after the cutting edges to the workpiece.

The kinematics of gear planing is made up of three simultaneous movements:

• The planing comb moves axially parallel to the workpiece, the teeth engage and remove a chip .
• At the same time, the workpiece rotates very slowly around its own axis,
• while the cutter comb also performs a straight-line movement perpendicular to the workpiece axis.

The workpiece rolls along the toothing of the cutter like a toothed wheel on a rack. The rolling on the straight flanks of the planer comb creates involute tooth flanks on the workpiece.

Since the planer comb usually has fewer teeth than the workpiece should have, it must be rolled several times over the active length of the planer comb. To do this, the tool is disengaged and the workpiece is divided into one or more gaps.

This process is repeated until the workpiece is toothed over its entire circumference. In this way, both straight and helical bevel and spur gears can be produced. For helical gears, only the comb has to be inclined by the angle of the toothing.

The tool is easy to manufacture compared to other gear cutting processes. The area of ​​application is large gears. However, since it is more uneconomical than hobbing, gear hobbing is of little importance.