CNC Helps New Gear Machine to Make the Cut

CNC is a universal language, but machine builders still require programming expertise to make their systems achieve optimal performance. Automation experts at NUM helped a Chinese machine builder, Betek, to speed the development of their new six-axis gear-hobbing machine, incorporating an electronic gearbox and CNC technology for gearmaking that help the Betek YK3132Z achieve exceptional cutting speed and processing efficiency.

The Betek YK3132Z reportedly is up to 10 times faster than conventional mechanical gear cutting machines, and more than twice as fast as other six-axis CNC gear hobbing machines.

Tianjin Betek Machinery Manufacturing Co. Ltd. (Betek) produces mechanical parts for industrial systems. The company uses machine tools in its manufacturing operations, and recognizing the opportunity to develop systems to supply China’s growing need for CNC gear cutting machines it began to develop the gear-hobbing line in 2013 with an estimated $13-million investment and a specially built manufacturing plant.

From the start of its development, Betek base the new machine’s power and programming on NUM’s Flexium+ CNC platform.

“Our main reason for choosing NUM’s CNC systems for our new gear hobber is that, unlike many competitive control products on the market, they have an open architecture,” explained Betek president and general manager Jin Guolin. “This provides an unrestricted foundation for development and customization work, helping us to reduce costs and shorten time-to-market significantly.”

Another factor in Betek’s choice of CNC supplier was NUM’s experience in gear-making applications. Its NUMgear-based CNC programs have been developed over several decades, and have been selected by numerous other machine builders.

Betek’s new YK3132Z six-axis gear hobbing machine uses NUM’s latest Flexium+ CNC kernel and high-end NUMDrive X servo drives together with compact BHX and SHX servomotors; high-resolution encoders and closed-loop control maximize accuracy of speed and position.

Both the turret spindle motor – a built-in model – and the table (C axis) torque motor are powerful direct drive units that are also controlled by a NUMDrive X servo drive. These motors completely eliminate the need for mechanical power transmission components such as worm and helical bevel gears, resulting in precision, backlash-free movement.

The turret spindle can handle speeds up to 1,200 RPM, while the table can rotate at up to 280 RPM; this allows use of the latest high-speed cutting tools. Accuracy and reliability are further enhanced by the machine’s use of high rigidity servomotor-driven precision ball screws for its linear axes.

The NUMgear production software suite includes dedicated hobbing functions and a precision electronic gearbox that allows all master axes and the turret spindle to be fully synchronized. The electronic gearbox minimizes synchronization time by predicting the acceleration rate as well as the speed of the axes.

All human interaction with the gear hobbing machine is via a NUM FS152i operator panel with a custom HMI. The operator panel features a 15-inch high-resolution backlit LCD screen with 22 large function keys and contains a powerful industrial PC. The HMI makes extensive use of graphics and is inherently intuitive; users can operate the machine after just a few hours of simple training. Gear manufacturing data can either be input using a simple ‘fill in the blanks’ method or derived from previously processed parts – the software includes database management functions.

Changzhou Mactool Precision Machine Tools Co. Ltd., a developer of gear-cutting machines and user interface software customized an HMI program for the machine. Florian Schmidt, NUM’s product manager, pointed out that Mactool and NUM China have collaborated on several high-value CNC machine projects in recent years, adding that: “To provide our customers with their ideal solution, we combine the best of all worlds.”

The Betek six-axis YK3132Z gear hobber accommodates gear blanks up to 320 mm (12.6 inches) in diameter. Its advanced CNC system can handle five-axis interpolation, enabling complex gear tooth profiles to be created smoothly and efficiently. The entire gear is cut as part of a single process, without interim removal/reinsertion of the gear blank or manual tool changeover.

Virtually any type of gear can be cut, including unusual types such as parallel shaft, herringbone, taper and non-circular gears. For maximum machining accuracy the machine uses dry cutting techniques, capable of achieving Level 6 precision on interim cut gears and Level 3 precision on finished products. Dry cutting also obviates the need for cutting fluid, which is a common form of pollutant in machining industries that requires special treatment and disposal.