Cold Forming Process Axial Gear Cutting with Fully Electric Drive Axles

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When it comes to precisely and efficiently producing small internal gearings in the cold forming process, axial gear cutting comes into play. Since the teeth to be manufactured are the direct negative form of the tool, this process achieves high profile accuracy as well as high material strength and material efficiency.

In the profiling of rotationally symmetrical workpieces using cold bulk forming, Profiroll Technologies GmbH can draw on extensive expertise. Until now, all machines produced by the company from Bad Düben have generated profiles through a rolling process—regardless of whether they are threads, ball screw profiles, or external and internal gearings. "However, this method leads to a technological limitation for components with relatively large inner diameters, especially in the case of internal gearings," says Dr.-Ing. Michael Hirsch, head of the "New Technologies" division at Profiroll. Profiroll is now addressing this gap in its machine range with the new axial gear cutting machine PA 450. The company sees the main application area in the production of rotor shafts for electric vehicles.

A New Process Was Necessary for Portfolio Expansion

With a view to expanding the portfolio and responding to specific customer inquiries from the automotive sector, small internal gearings have also come into focus in recent years. A suitable manufacturing process had to be developed and implemented. "In 2022, we first engaged theoretically with this process, specifically regarding tool design. Initial process investigations were conducted in 2023 using a special fixture with hydraulic drives," Hirsch reflects.
 During this time, the disadvantages of hydraulic drives for such a process became evident. "They are limited in speed and are comparatively large and expensive because pressure accumulators are needed to achieve the corresponding process dynamics," Hirsch continues. Consequently, the developers at Profiroll turned their attention to electric drive systems. By the end of 2024, the first promising trials with electrically driven axes, specifically a planetary roller gear, were tested for this application. In just eight months of development time, a novel machine for internal gearing was created, featuring electromechanical drive axes for high-dynamic and fast sliding movements. The new forming machine operates quietly, features low energy consumption, and is compact in size, requiring minimal maintenance.

Elevating Internal Gear Cutting to a New Level

With the axial gear cutting machine PA 450, the tool profile is transferred to the workpiece not in a rolling process but in an axial process. In line with the vertical machine setup, the component is processed in the axial direction. It is formed from below with a view to optimal lubrication supply to the forming zone.

Profiroll has also oriented the development and design of the system according to common customer requests. These are mostly aimed at depicting only an internal gearing. The new PA 450 can process components with a length of 50 mm to 450 mm (approx. 2 to 18 inches), a diameter of 30 mm to 100 mm (approx. 1 to 4 inches), and a tooth diameter of 15 mm to 60 mm (approx. 0.6 to 2.4 inches), and a number of teeth ranging from 17 to 100, with a focus on straight gears.

For process visualization, Profiroll's developed user interface is used, ensuring intuitive handling. Important parameters are graphically displayed, including visualization through a force-displacement diagram. Profiroll's stated goal is to replicate the same quality criteria in the forming of internal gearings as with its other Profiroll system technologies. "With this machine, we want to elevate internal gear cutting to a new level and provide our customers with a system designed for high efficiency," says Michael Hirsch.

*Freelance Author