Basic principle of gear hobbing

Gear hobbing is cutting by using the meshing principle of helical gear. The essence of hob is a worm, and the workpiece is the gear meshed with it. During gear hobbing, the hob and the workpiece make generating motion under a certain speed ratio, and make axial feed motion relative to the full tooth width of the workpiece. By adjusting the meshing speed ratio, gears with the same modulus and different number of teeth can be machined with only one tool.

Hobs with different tooth shapes can also process gears with various tooth shapes such as turbine, sprocket, spline and cycloid gear. Gear hobbing machine generally carries out three movements at the same time: cutting movement, that is, the rotary movement of hob; Generating motion, i.e. tooth splitting motion; Vertical feed motion, that is, the cutter walking motion of the hob along the gear blank axis. Among them, the gear splitting transmission error directly affects the gear cutting accuracy.

The basic principle of gear hobbing involves the synchronized rotation of the gear blank and the hob to progressively cut the teeth into the blank, creating the desired gear. Here’s a breakdown of how this process works:

  1. Hob and Gear Blank Alignment: The gear blank and the hob (a specially designed cutting tool that resembles a worm gear) are mounted on their respective spindles in the hobbing machine. The hob is positioned at an angle corresponding to the helix angle of the gear to be cut, ensuring that the teeth are properly aligned with the axis of the gear blank.
  2. Synchronized Rotation: The hob and the gear blank are rotated in a synchronized manner. The synchronization is such that for every complete turn of the hob, the gear blank rotates by an amount corresponding to one tooth space. This synchronization is crucial for ensuring that the hob cuts the teeth accurately and uniformly around the gear blank.
  3. Axial Feeding of the Hob: As the hob rotates, it is also fed axially across the face of the gear blank. This axial movement, combined with the rotation of the hob and the gear blank, allows the cutting edges of the hob to progressively remove material from the gear blank, forming the teeth.
  4. Continuous Cutting Action: The hob is designed with a series of cutting teeth arranged helically around its circumference. This design means that as the hob rotates, multiple teeth are engaged in cutting the gear blank at any given time. This continuous cutting action makes gear hobbing a highly efficient process for generating gear teeth.
  5. Generation of Gear Teeth: The combined rotational and axial movements of the hob and the gear blank result in the generation of the gear teeth. The shape of the gear teeth is determined by the profile of the hob’s cutting edges. As the hob moves across the gear blank, it cuts the full depth of the gear teeth, completing the gear manufacturing process.

In summary, gear hobbing is a gear manufacturing process that uses a hob to generate the teeth of a gear. The process relies on the synchronized rotation of the gear blank and the hob, combined with the axial feeding of the hob, to cut the gear teeth with precision and efficiency. This method is widely used for producing a variety of gear types, including spur, helical, and worm gears, due to its versatility and the high quality of the gears it produces.

In terms of gear processing principle and process characteristics, gear hobbing is better than gear shaping, gear extrusion and gear rolling, so that gear hobbing can process cylindrical straight, helical gear, conical gear, turbine, spline and other tooth parts, and because the structural type and production efficiency of the tooth parts processed by it have advantages that are difficult to complete or incomparable to other processing processes, The market share of gear hobbing machine in gear processing equipment is much more than that of other gear processing machines.

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