The electric transition of heavy commercial vehicles, such as trucks, requires transmission technology made from gears with larger diameters, larger modules and finer roughness. Here is the challenge that gear and machine manufacturers are facing to meet the new market demands.
The transmission is subjected to different loads than in the past and must be made much more precisely. At the same time, transmission efficiency is a top priority by requiring low friction to minimize energy consumption and maximize vehicle range.
The new grinding machines
A whole series of Kapp Niles gear grinding machines are used at the Mercedes-Benz plant in Gaggenau for fine precision machining. For large gears, a new KNG 350 flex machine was purchased, which is suitable both for use in the prototype areas up to large series production. With the option of enlarging the work area and the use of combination grinding wheels up to 200 mm wide for superfinish grinding or polishing applications, large gears can be efficiently machined for e-mobility.
The KX 260 TWIN and KX 260 TWIN HS machines with small tools are used for gear shafts and enable continuous-generation grinding with dressable and non-grinding tools. The concept involves two identical workpiece spindles arranged opposite each other on a rotary table. Parallel to the machining of one workpiece, loading and unloading takes place, including the alignment of another workpiece on the second spindle.
Polishing superstar
When it comes to Polishing for commercial vehicles, increased side-loading capacity of gears and improved efficiency are essential. Kapp Niles machines use special worm wheels with two areas, one for conventional grinding and one for polishing grinding, making it possible to produce gears with roughness as low as Rz < 1 μm in a single take. “By now, polishing has been implemented across the entire line of electric gears,” the company explained.
The key challenge is to maintain stable roughness quality in mass production.
Large components
“When the design for the KNG 350 flex was developed, the focus was already on large components for truck transmissions, but at the time these were components with a diameter of about 300 mm. With the electric transmission, gears up to almost 400 mm in diameter have suddenly appeared. This affects both the work space and the handling area,” said Markus Reißenweber, sales manager Europe and America at Kapp Niles. With a weight of about 30 kg, the components have a heavier weight and a larger module that require new processes, such as polishing grinding and preparation for mass production, so they can run smoothly in three shifts.
(by Martin Witzsch)