Principle of CNC gear hobbing machine processing

Writer： admin Time：2025-01-03 09:20:07 Browse：175℃

Gear hobbing is equivalent to grinding the teeth of one gear in a pair of meshing spur cylindrical gears into cutting edges with front and rear angles, and using this gear as a gear hobbing tool for machining,

By forcibly maintaining a transmission ratio relationship of gear meshing between the gear hobbing cutter and the meshing gear blank, the gear hobbing cutter can perform reciprocating motion to envelop a qualified involute profile.

From the principle of tooth profile forming, gear hobbing also belongs to the expansion method.

(1) Main Movement. The up and down reciprocating motion of the hobbing cutter achieves cutting motion, expressed in terms of the number of reciprocating times per minute. 

The downward stroke of the gear hobbing cutter is the working stroke, and the upward stroke is the empty stroke;

 The commonly used gear hobbing machine generally uses a gear hobbing cutter with a reciprocating motion of 1200 to 1500 times per revolution,

To improve productivity, high-speed gear hobbing machines can use a gear hobbing cutter that moves back and forth 2500 times per revolution, which is 24 times more efficient than commonly used gear hobbing machines.

(2) Split tooth motion. Namely, it develops into motion, maintaining a meshing relationship between the gear hobbing tool and the workpiece through a pair of cylindrical gears. 

The forced meshing motion is provided by the transmission chain of the gear hobbing machine, that is, when the gear hobbing tool rotates one tooth, the workpiece also rotates one tooth,

Satisfy i=n knives/n knives=z knives/z knives (n knives and n knives are the rotational speeds of the hobbing knife and the workpiece, and z knives are the number of teeth between the hobbing knife and the workpiece).

(3) Circular feed motion. The arc length that the hob rotates on the dividing circle during each reciprocating stroke is the circumferential feed rate, measured in mm/double stroke. 

Therefore, the gear hobbing process is also a circular feed process.

The speed of rotation of the gear hobbing cutter determines the speed of rotation of the workpiece, and directly affects the cutting load of the gear hobbing cutter, 

as well as the surface quality, productivity, and service life of the gear hobbing cutter. Moderately increasing the circumferential feed rate can improve the gear hobbing efficiency.

(4) Radial cutting motion. When starting cutting, if the hob immediately cuts radially into the workpiece to the full tooth depth, it will damage the workpiece due to excessive cutting load.

 Therefore, the hob should gradually cut radially into the workpiece to the full tooth depth.

The gear hobbing cutter relies on mechanisms such as a cam to achieve radial feed. When cutting to full tooth depth, the radial feed stops, and then the full gear ring is cut out without feed. 

The radial feed rate is the radial cutting distance of the hob during each reciprocating stroke, measured in millimeters per double stroke.