Axial forming is a cold forming process in which a tube or bar is reduced in cross section or formed into a specific profile. Most applications involve the production of internal and external splines. To produce external splines, the forming tool, a die with the exact negative contour of the desired gear, is guided axially over the workpiece, thereby precisely reproducing the tool contour (Figure 1a). A major advantage of this process is the simultaneous forming of all teeth using a single-piece tool, which results in excellent total pitch deviation accuracy of the produced gear.

A key feature of axial forming is modulation, where the specific force profile is shown in Figure 1b. In this approach, the forming process does not occur in a single forward stroke across the entire forming zone, but rather through a series of small, incremental forward and backward strokes. The highly loaded forming zone is exposed by short backward strokes performed between the forward strokes, allowing for relubrication. The continuous renewal of the lubricant film ensures optimal friction conditions, resulting in a significant reduction in forming forces. This is particularly beneficial for spline forming on thin-walled components without bulging or buckling, while also increasing tool life and enabling the use of simple lubricating oils. Compared to conventional extrusion processes, incremental axial forming is especially suitable for producing functional elements such as splines. Due to the locally confined forming zone and reduced process forces, components can be formed without negatively affecting adjacent areas of the component. In this process, the material is not removed but is targeted for displacement, which largely preserves the material’s fiber orientation and redirects it along the profile contour. Combined with a more uniform stress distribution within the component, this leads to improved mechanical properties, particularly with regard to fatigue strength and load-bearing capacity. At the same time, the lower forming forces enable more precise compensation of elastic deformations, resulting in high dimensional and profile accuracy. While axial forming, with its process‑specific advantages for producing splines, is already well established both technologically and industrially, the manufacture of axially formed helical gears presents entirely new challenges in terms of process kinematics, machine design, drive control and tool design. The results of numerical and experimental investigations, including a new generation of machines equipped with an additional electric rotary drive for the axial forming of helical gears, are outlined below.