The increasing demand for efficiency and noise emission of gears pushes the gear grinding process to its limits. With the widening range of applications for automatic planetary transmissions and increased number of speeds (currently up to 10), gears in average get smaller and smaller, while production volumes are increasing. The same applies to industrial applications, like for example geared motors which are currently introduced in many actuation systems, even in private homes. The vast majority of this kind of gears fits into a range of 160 mm in diameter and below a module of 3 mm.

Unfortunately, smaller gears result in shorter grinding times and, if the machine is not capable of significantly shortening the non-productive time, the ratio of productive vs. non-productive time is getting from bad to worse. Especially for planetary pinions, grinding times are currently down to 6-7 seconds, so that a non-productive part change of 5 seconds can easily result in a machine utilization of less than 50%.

Over the past decade, productivity in hard gear finishing, and especially in threaded wheel grinding, has not evolved much. Grinding technology, tools and application data have reached a state of the art that cannot be improved significantly any further – at least for the time being. Therefore, stiffness, stability and speed of the gear generating grinding machine have become the main design targets for the gear grinding process.

Gear grinding machine - Samputensili
Figure 1: Each linear slide carries a workpiece spindle

New machines have been introduced by a variety of suppliers; however, they all follow similar concepts, which for technical reasons do not allow a production improvement because of constraints of the concept itself. Most current gear grinding machines have 2 workpiece spindles to reduce non-productive times when changing parts. While a gear is ground on one spindle, parts are changed on the other. Despite this, the non-productive time has never gone under 5 seconds because the spindles are located on a rotary table which is hydraulically locked in position, but is inaccurately floating while moving. Unlocking, settling after moving and locking it into the new position take more time than the motion itself and cannot be any faster by design.

The Samputensili G 160 presents a unique, new design to finally solve this. Furthermore, it optimizes static and dynamic stiffness compared to current standard machine architectures.

In the gear grinding process, instead of using a rotary table to carry the workpiece spindles, the gear grinding machine G-160 splits the X-axis of current machines into two linear slides (X1, X2), each of them carrying one workpiece spindle, thereby eliminating the rotary table and all the constraints connected to it. Both work-spindles and the associated radial X-axis slides are under full position control anytime and both can be moved in and out of the workspace simultaneously without interfering with each other. This is the first time ever that “On-the-Fly” synchronization between workpieces and the grinding wheel can fully be utilized. Even better, repositioning the grinding wheel for the next part can also be done at the same time. No axis is waiting for another – everything moves simultaneously!

Being driven by high-dynamic linear motors, the change of workpieces comes down to less than 2 seconds including meshing, synchronization and simultaneous repositioning of the tool. And this is achieved not by overcharging machine components, but by the unique concept of the Samputensili G 160 gear grinding machine.

gear grinding machine Samputensili
Figure 2: Virtual shifting axis