Particular precision is essential for the e-drive market: Many components require perfect surfaces – this ensures smooth running at the high torques of the electric motor. The example of “tooth flank grinding” with machines from EMAG SU shows how suppliers, general transmission manufacturers and OEMs can implement this requirement: The grinding specialists have, for example, a special axis concept in the G 160 machine that guarantees microscopically perfect surfaces. A conversation with Alexander Morhard from EMAG SU about EMAG SU’s mechanical engineering solutions for tooth flank grinding.
Perfect surfaces for e-mobility
Mr. Morhard, why is tooth flank grinding particularly important for e-motor components?
The high torque of the electric motor leads directly to special dimensional and surface requirements. This can be seen in the tooth flank machining of shafts and gears, where even minimal waviness in the surface appearance can trigger certain interference noises in the drive. That’s why it’s all about dimensionally accurate results in the mµ range here – and with the shortest possible cycle times. For this, you need special grinding solutions.
What kind of know-how does EMAG SU bring to the table here?
We have a great deal of experience in this area and have been developing high-quality grinding machines for technologies such as topological grinding or superfinishing for many years. The G 160 is the fastest machine on the market for components up to module four with a maximum outside diameter of 160 millimeters. It has a chip-to-chip time of just 1.6 seconds.
How do you achieve this speed?
The machine has two parallel workpiece tables that move alternately at high speed to the grinding wheel. So while one part is being machined, the internal loading robot inserts a blank into the other spindle or unloads the finished part beforehand. The grinding wheel is centered on the pre-toothed workpiece directly on the workpiece spindle in parallel with the machining time. By the way, the 1.6 seconds mentioned is an enormously small value compared to grinding machines with rotary tables, where it can take up to five seconds to perform the same process.
What is the overall effect of the difference?
The grinding time for a typical component, such as a planetary gear, is only ten seconds. Consequently, the difference in chip-to-chip time becomes a real game changer: the total cycle time for a component drops significantly from around 14 to 12 seconds, and output rates increase massively.
What does the G 160 achieve in terms of component quality?
Our axis concept ensures exceptional surface quality: there is no tangential axis on the G 160. Instead, the existing Y and Z axes move simultaneously, creating a “virtual” tangential axis. As a result, the contact point of the grinding wheel to the workpiece is around 100 millimeters closer to the pivot point of the swivel axis, which has a favorable effect on the vibration behavior during grinding. The result can be seen again, in the surface structures of the finished component: The minimal waviness in the surface appearance mentioned above disappears almost completely.
What solutions are available from EMAG SU for larger components?
There is a large selection of solutions available. For example, the G 250 machine is suitable for components up to module seven with a maximum outside diameter of 250 millimeters. Axle drive gears, gear wheels or shafts with a maximum length of 550 millimeters can be finished with this solution by generating grinding or profile grinding with short cycle times. The G 250 has two table spindles for this purpose. In the G 250 HS variant, the machine also has a high-speed grinding head (max. 20,000 rpm), in which both generating grinding and profile grinding – with very small generating or profile grinding wheels – can be performed on the main grinding spindle. For components with interference contours, many users often use the faster generating grinding (instead of profile grinding), which results in significantly shorter grinding times. Overall, we place a lot of emphasis on the flexibility of our machines.
Finally, can you give us an example of an EMAG SU machine that is used outside of e-mobility?
For larger components in trucks or in general transmission manufacturing, the cost-effective G 400 rounds off our range at the top end. The machine has a tool table for components with a maximum diameter of 400 millimeters and a shaft length of up to 750 millimeters. Many users find it interesting that this machine can also be loaded from above, because the housing has an over-corner door. In addition, it is important that we configure the machine very flexibly in terms of tooling and dressing technology. It also has fast automation and high user-friendliness – the work spindle mounted on a rotary table facilitates loading or unloading as well as tool handling.
Overall, how do you see EMAG SU’s market opportunities in hard fine machining?
We are ideally positioned for many grinding tasks – especially within e-mobility. Currently, for example, a French automotive manufacturer is successfully using several grinding machines from EMAG SU in this area. In the next few years, we want to make greater use of our strengths in the production of ultra-fine surfaces with very different contours in the growing market.
Are there other technological advantages with this machine?
First of all, it is important that generating grinding and profile grinding take place on the main grinding spindle, so the machine does not have a heat path, as is the case when using attachment spindles for profile grinding on other machines. In addition, users can change over the G 250 for the other process in a matter of minutes. It is also interesting to note that many parts with interfering contours can be roll ground by using generating grinding worms, up to a 68 mm foot circle. This results in very short grinding times. All other components can be finish ground with a profile grinding wheel as small as 30 millimeters. Centering takes place in the loading position during machining. The integrated dressing unit provides additional process reliability.