Abstract: The development process of gear honing technology and the latest advancements in powerful gear honing technology among the world’s major gear machine tool manufacturers. It introduces the advantages of powerful gear honing, elaborates on the key technologies of powerful gear honing, and finally, provides an outlook on the further technological development trends of powerful gear honing machines.
1. Introduction
The carrying capacity, smooth motion, and service life of gears primarily depend on the contact conditions of the mating tooth surfaces under actual working conditions. The micro-geometric morphology of the tooth surface has a significant impact on gear vibration noise and service life. Employing hard-surfaced precision-machined gears can effectively enhance the load-bearing capacity of transmission devices, reduce noise, decrease vibration, and extend service life. Critical power transmission devices have universally adopted hard-surfaced precision-machined gears. There are various precision machining methods for hard-surfaced gears, such as gear grinding, gear skiving, gear lapping, high-speed dry cutting, and gear honing. Gear grinding is the most widely used and mature process, featuring high precision and efficiency but with higher costs. Additionally, the micro-geometric morphology of the gear-ground tooth surface is not conducive to reducing transmission noise. Gear skiving is suitable for large-scale hard-surfaced gear machining but falls behind in precision and efficiency compared to large-scale CNC form grinding. With the development and maturation of large-scale gear grinding equipment, the application of gear skiving has gradually decreased. Gear lapping is mainly utilized in the precision machining of bevel gear pairs. High-speed dry cutting technology is widely applied in the precision machining of small modulus gears. Gear honing can achieve an ideal micro-geometric morphology of the tooth surface, especially with unique tooth surface textures, which significantly inhibit the vibration noise of transmission devices. Therefore, gear honing technology has been continuously applied and developed, especially in the precision machining of automotive gears.
Different precision machining solutions each have their unique advantages. However, comparing the entire gear machining process, with the rapid development of modern CNC gear machining machines, the finishing allowance has been significantly reduced, and the quality of gears before finishing has continuously improved. Furthermore, as the market’s demand for comprehensive gear performance further increases, it not only pursues high precision but also focuses on aspects such as meshing noise, contact quality, service life, processing costs, and energy consumption. This requires gear precision machining processes to be more environmentally friendly, energy-saving, and emission-reducing. Gear honing technology can well meet these demands. Coupled with the new functionalities endowed to gear honing machines by modern CNC technology, it will bring a broader market for the development of gear honing technology.
This paper reviews the development process of gear honing technology and the latest advancements in powerful gear honing technology among the world’s major gear machine tool manufacturers. It introduces the application of new technologies and processes in powerful gear honing machines and provides an outlook on the further technological development trends of powerful gear honing machines.
2. Technical Progress in Gear Honing Processing
2.1 Soft Gear Honing
Traditional gear honing employs a gear-shaped or worm-shaped honing wheel to engage freely with the gear to be honed, equivalent to a pair of crossed-axle helical gears in transmission. It utilizes the relative sliding and pressure between the mating tooth surfaces for honing, primarily used for the finish machining of hardened gear tooth surfaces. The gear honing wheel is made of a somewhat elastic synthetic resin or artificial rubber. In the freely engaged state, the honing wheel mainly serves a finishing function with limited material removal capacity and limited correction ability for gear precision. The error reproduction phenomenon is difficult to suppress, and the gear precision primarily depends on the previous cutting and heat treatment precision.
Table 1: Comparison of Traditional Gear Honing Methods
| Honing Method | Material of Honing Wheel | Primary Function | Material Removal Capacity | Gear Precision Correction Ability |
|---|---|---|---|---|
| Soft Gear Honing | Synthetic Resin/Artificial Rubber | Finishing | Limited | Limited |
2.2 CBN Wheel Hard Gear Honing
In the 1980s, hard honing wheel honing technology was developed abroad. It uses medium carbon steel to make a gear-shaped honing wheel substrate, and the superhard abrasive is coated onto the tooth surface of the steel substrate using an electroplating deposition method. It relies on the superhard abrasive on gear honing wheel tooth surface to hone the workpiece, enhancing the material removal capacity. The rigidity of gear honing wheel is improved, allowing it to not only finish but also correct gear tooth shape, pitch, and tooth orientation errors, significantly improving gear precision.
Table 2: Comparison of Soft and Hard Gear Honing
| Honing Method | Material of Honing Wheel | Rigidity | Material Removal Capacity | Gear Precision Improvement |
|---|---|---|---|---|
| Soft Gear Honing | Synthetic Resin/Artificial Rubber | Low | Limited | Limited |
| Hard Gear Honing | Medium Carbon Steel with Superhard Abrasive | High | Enhanced | Significant |
2.3 Powerful Gear Honing Technology
As gear precision requirements continuously increase, with greater emphasis on surface quality, gear manufacturing powers have actively incorporated advanced technologies such as electronic gearboxes, automatic loading and unloading, in-machine inspection, error correction, direct drive, and CAM into gear honing machine manufacturing. They have developed a series of powerful gear honing machines with distinctive features. The honing wheel and workpiece are forcibly engaged, providing strong correction capability for gear precision and significantly improving gear precision, with powerful gear honing accuracy reaching DIN grade 5 and a surface roughness Ra of less than 0.2 μm.
Gear honing technology is no longer merely an auxiliary finishing process but can be used as an independent precision machining method, complementing grinding processes. The development of gear honing technology.
3. Advantages of Powerful Gear Honing
As a solution for gear precision machining processes, gear honing has been continuously applied and developed. Powerful gear honing breaks the limitation that traditional gear honing can only be used for gear finishing. It introduces electronic gearbox control, ensuring stable and controllable engagement between the honing wheel and the workpiece, improving the stability and consistency of precision, making it more suitable for large-scale precision gear production needs, especially in the production of automotive transmissions.
The advantages of powerful gear honing are mainly reflected in the following aspects:
(1) The Tooth Surface Texture of Honing Reduces Gear Vibration Noise
Vibration noise has always been a critical evaluation index for precision gear transmission devices. Numerous experimental studies have shown that the tooth surface texture has a significant impact on gear vibration noise, especially in high-speed transmission devices. Unreasonable tooth surface textures can cause high-frequency resonance. During honing, the gear honing wheel and gear are in a crossed-axle engagement state, with composite relative sliding along the tooth profile direction and the tooth width direction forming a unique honing arc texture, which can significantly reduce gear transmission noise. Low-noise grinding technology, researched and promoted in grinding, utilizes CNC technology to disrupt regular grinding textures during the grinding process, forming tooth surface textures similar to honing arc textures.
(2) Higher Compressive Stress on the Tooth Surface Can Be Obtained by Honing
The stress state on the gear surface has a significant impact on gear life, especially as the cleanliness of gear steel continuously improves, and the failure mode of gears shifts from macroscopic pitting to surface microscopic pitting. The stress state on the surface becomes the main contradiction determining gear strength and life. Honing can achieve higher residual compressive stress on the tooth surface, effectively improving gear strength, wear resistance, and corrosion resistance.
(3) Gear Honing Can Avoid Tooth Surface Burns
Gear honing removes material through relative sliding on the tooth surface, with low cutting speeds, preventing thermal effects on the tooth surface and avoiding tooth surface burns. Grinding burns have always been an indicator that needs strict control in grinding processes. A large amount of grinding heat changes the stress state of the tooth surface, causing microcracks and affecting gear life.
(4) Better Tooth Surface Roughness Can Be Obtained by Honing
Gear surface quality is increasingly receiving attention. Composite grinding processes are also used in grinding to achieve small roughness values, but processing costs increase. However, the machining mechanism of gear honing allows it to achieve smaller tooth surface roughness values economically, reaching Ra < 0.2 μm. With optimized processes, mirror finishing of the tooth surface can be achieved.
(5) Gears with Shoulders Can Be Processed by Gear Honing
Grinding requires a certain amount of protrusion (over-travel), making it difficult to process gears with stepped shafts or other interfering structures. Using small-wheel form grinding can process gears with a certain amount of undercut, but the wheel is small and wears quickly, requiring frequent wheel replacement, which is difficult to meet the needs of batch processing.