Latest advancements in gear grinding technology

Gears machined by grinding offer advantages such as low transmission noise, high transmission efficiency, and long service life. Gear grinding was once considered an expensive gear machining method used only in aerospace or other high-tech fields. However, perceptions have changed: improved grinding machine efficiency and better grinding wheel performance have significantly reduced costs. As a result, gear grinding has begun to be widely used in gear manufacturing, such as in the production of automotive and motorcycle gears, and has reached a level of widespread application. In fact, all Tier 1 automotive gear suppliers now commonly possess gear grinding machines to remain competitive. The automotive industry is expected to become the largest growth market for hardened gear surfaces in the next 2-5 years. Because gear grinding eliminates heat treatment distortion, many gearboxes use ground gears to better control transmission backlash and noise. Gear grinding technology is now largely mature and rapidly growing throughout the gear industry.

  Advances in gear grinding machines

Today's gear grinding machines are far more efficient than similar machine tools from ten years ago. This is due to a series of major improvements:

1. Airborne Measurement

Many gear grinding machines have become more precise thanks to the addition of onboard measurement systems. By using onboard measurement, gears no longer need to be removed from the worktable and sent elsewhere for inspection, avoiding secondary installation errors during reprocessing. During machining, the onboard measurement system first performs a preliminary analysis of the gear, then compares the measured parameters with the theoretical design parameters to determine the required correction. The control system collects this correction data and automatically adjusts the gear grinding process before grinding and measurement are performed again. This cycle is repeated until the required accuracy is achieved. Integrated onboard measurement and correction systems make modern gear grinding machines more efficient.

In China, for example, Qin Chuan Development Co., Ltd.'s YK75100 forming wheel gear grinding machine, paired with the Chengdu Tool Research Institute's CEP 1000 top-mounted gear measurement system, has successfully attempted open-loop in-machine measurement (although feedback and control of the measured data still require manual intervention). However, considering the overall level in China, the accuracy of machining and measurement still needs further improvement.

2 Direct drive motors

In recent years, the use of compact direct-drive motors in grinding wheel spindles and gear spindles has been increasing. Direct-drive spindles can avoid transmission chain errors. Therefore, using direct-drive motors in the "dressing grinding wheel - grinding gear" cycle, along with better grinding wheels and multi-axis linkage control, can eliminate high-frequency errors and harmful vibrations such as cutting marks, distorted geometry, gear noise.

3. Automation

The term "automation" is increasingly being used in gear grinding, especially in process-oriented production, including workpiece mounting, tool changing, and inventory sorting synchronized with the workpiece flow. Automation eliminates machine idle time and helps reduce waiting time between processes.

4 Gear Grinding Machine Software

Windows-based software, much like that used in personal computers, is widely used in today's gear grinding machines (such as Windows-based design systems and CNC systems). Previously, drawings could only be made on paper; now, design and correction software packages combining graphical interfaces and algorithmic software enable programmed gear geometry design and localized manufacturing simulation.

High-precision closed-loop control among the drive, ball screw, and position sensor is achieved through software applications. Many components of the new generation of gear grinding machines are equipped with position sensors separate from the drive unit, thus achieving higher accuracy and thermal stability. Absolute displacement sensors and absolute encoding technology ensure high-speed transmission of feedback data and stability of machine tool transmission while maintaining high positioning accuracy.

5. Machine Tool Appearance

Today's gear grinding machines are smaller and take up less space, allowing manufacturers to make better use of limited production areas to "create" more usable space instead of spending money on "bricks and cement" to expand factory buildings, and instead on purchasing equipment.

6 New Material Grinding Wheels

Advanced ceramic-bonded grinding wheels offer the same high productivity as electroplated cubic boron nitride (CBN) grinding wheels. The use of new materials in "hybrid particle" composites and advancements in bonding processes have improved the strength, toughness, shape retention, material removal force, and durability of ceramic-bonded grinding wheels. These superior properties stem from the high-performance particle structure and increased porosity. Simultaneously, the favorable particle structure reduces grinding stress and lowers grinding temperature.

Currently, the use of new cold-grinding ceramic abrasives with high-pressure coolant systems has made the choice between electroplated CBN wheels and ceramic-bonded wheels more difficult. However, electroplated CBN wheels are simpler to operate, require less installation time, and have lower operator skill requirements than ceramic-bonded wheels, offering a more feasible and cost-effective alternative to CBN abrasive ceramic-bonded wheels.

Reishauer, an American company, tested these ceramic grinding wheels using their "cold grinding" process and concluded that: ① The latest alumina and ceramic abrasive grinding wheels can generate the same or less pressure as CBN abrasive ceramic bonded grinding wheels. ② Contrary to expectations, ceramic grinding wheels are more efficient and durable than CBN grinding wheels. ③ Unlike electroplated CBN grinding wheels, ceramic grinding wheels can be re-sharpened on a gear grinding machine, while electroplated CBN grinding wheels must be sent back to the manufacturer for regrinding.

Ceramic grinding wheels offer high cutting speeds (e.g., 60 m/s), making them suitable for large-scale gear production. These grinding wheels also have a longer service life than previous types (such as alumina grinding wheels). This new grinding wheel technology is increasingly used in worm gear grinding wheels for grinding gears of 200 mm and smaller, which have the highest production volume.

7. Reduction in grinding costs

Today, the cost of gear grinding has dropped significantly for many reasons, such as high-performance models based on modular design, CNC systems, and streamlined production. Even gear grinding machines that incorporate all of the aforementioned advanced technologies are much cheaper than previous models. Mass production has shortened the production cycle of a single piece by 50% to 70%, and the cost of consumables (grinding wheels and diamond dressers, etc.) has also dropped significantly.