Technical Column

New Generation Grinding Technology


What do gears in trains, wind turbines, reducers, marine transmissions, off-road equipment and printing presses have in common? They must run quietly, withstand heavy loads, have excellent pitch changes, be very accurate, and have a long service life. This usually means finishing the gear with a post-heat treatment process, most commonly grinding. The solution is the RZ1000, which is the latest generation of large-scale continuous gear grinding machines produced by Reishauer. Making larger gears in a smaller footprint is a challenge for all manufacturers, in part due to high material / manufacturing costs, pressure on timelines, and the level of technology required to produce such high-speed gears. There is no doubt that compared with single-tooth profile grinding technology-although this process has been significantly improved over the past ten years, continuous single-sharp grinding has the lowest cost per piece, the highest yield, and superb indexing accuracy . To grind large gears, the key factors that a machine must have include dynamic stiffness, flexibility, short adjustment and run times, and on-board inspections.

If the controller is regarded as the brain of the machine tool, then the working spindle hypothesis can naturally be regarded as the heart. In order to transfer smooth movements, high torque, and the necessary spindle speed from grinding to inspection, an unconventional method is required.

For such applications, the table drive is quite unique and patented. The toothless planar transmission provides static and dynamic stiffness unmatched by any comparable machine tool. This friction transmission also eliminates the “ghost” frequency of previous designs because there are no gear teeth in the transmission assembly.

The design also enables a wider range of speeds for the workpiece shaft and is not limited by spur / helical gear sets or copper worm gears and steel worms as traditional designs do. The “direct drive system” was initially considered, but it did not achieve the desired results and brought some new spindle speed limits to the spindle speed. A set of high-precision rotary encoders synchronizes the axis with the other rotary axes of the machine.

The machine controller, or “brain,” is the next key factor in the solution chain. From a grinding and inspection standpoint, the ideal prerequisites for a controlled process are a high-speed, ultra-precise “spread” module and a flexible operating system. Based on the configurable design concept, the Siemens 840D CNC system provides an ideal platform for the integration of electric gearboxes and human-machine interfaces (see Figure 2). Key features include:

◆ Windows operator interface, which can input data in real time during operation and machining, which facilitates rapid online optimization

◆ Open structure allows users to program almost any geometry and grinding, dressing and inspection technology functions to improve quality and efficiency

◆ Display of supported diagnostic systems for all key machine functions, including possible connections to external networks

◆ Display supported diagnostic system for basic process analysis with graphical auxiliary error checking function

◆ Using Reishauer technology software to help operators automate computer bed data sets during data entry

◆ Comprehensive safety functions for axis monitoring (SSI) to protect operators and machine tools

◆ With the help of automatic or manual electronic handwheel, all related adjustments and drive shafts are moved to adjust the machine safely and quickly