The machining principle of a CNC gear hobbing machine is based on the generating method (also known as the generating method). Through the precise meshing motion between the hob and the workpiece, the involute tooth profile of the gear is gradually formed. The entire process is precisely controlled by a computer numerical control (CNC) system to ensure high-precision machining.
Its core principle can be summarized as follows:
Gear Hobbing Basics: Gear hobbing simulates the meshing process of a gear and rack. The axial profile of the hob is similar to a rack; when the hob rotates, it is equivalent to an infinitely long rack moving continuously along the axial direction. The workpiece (gear blank) rotates synchronously in mesh with this "virtual rack," thus forming the involute tooth profile on the blank.
Key Motion Components:
Main Motion: The hob rotates at high speed, achieving the cutting action.
Gear Splitting Motion (Generating Motion): The workpiece rotates at a specific transmission ratio (determined by the number of hob heads K and the number of workpiece teeth Z), ensuring that the hob feeds axially one or more tooth pitches per revolution, forming the correct tooth profile.
Axial Feed Motion: The hob moves along the workpiece axis, gradually cutting out the entire tooth width.
Machining Differences Between Different Types of Gears:
Spur Gears: The hob axis is parallel to the workpiece axis; machining is completed only by generating motion and axial feed.
Helical Gears: The hob holder needs to be tilted at a helix angle, and additional rotational motion (differential compensation) needs to be introduced to match the helix direction of the helical gear, achieving precise envelope.
Core Role of the CNC System: Modern CNC hobbing machines utilize electronic gearbox technology, precisely controlling the linkage between various axes (such as the hob rotation B-axis, workpiece rotation C-axis, radial X-axis, and axial Z-axis) through software, replacing traditional mechanical transmission chains and significantly improving flexibility and precision. Technologies such as full closed-loop control and mechanical backlash compensation further ensure that the machining accuracy can reach level 6 of the GB/T10095.1-2008 standard, meeting the needs of high-end fields such as new energy vehicles.