Gear grinding is currently attracting a lot of attention, especially in the production of components for electric drives. Production planners are demanding new solutions for a perfect surface that assures their necessarily smooth running at high speeds and heavy torque loads. To see how a high-tech niche machine builder implements these requirements, one need look no further than EMAG SU “tooth flank grinding” machines.
The gear grinding machine specialist, based near Bologna Italy, developed the G 160 model, for example, which features a special “virtual” axis concept for microscopically near-perfect surfaces. At the same time, the integrated material handling technology keeps the cycle times down to a minimum.
Electromobility is booming and the competition to have the best solution is accelerating. Almost all automotive manufacturers launched new EV models in 2022. What does this mean for the production planning by OEMs and suppliers?
“On the one hand, they have to effectively deal with growing production quantities, yet, still have to guarantee an ever-increasing level of quality, because the high torque load of an EV electric motor results in special requirements for tight tolerance dimensions and surface finish,” said Alexander Morhard, technical gear support specialist with EMAG SU. “This development is particularly noticeable in the machining of tooth flanks on shafts and gears. Here it is important to achieve dimensionally accurate results in the micron (µm) range, because even minimal ripple in the surface finishing of the components can cause interference noise in the drive performance.”
G 160: minimal chip-to-chip times
With a wide range of technological innovations, EMAG SU demonstrates how quality can be improved in this extremely precise application. The company offers a large range of machine tools that cover the entire gear tooth cutting process. Tooth flank grinding, with the alternative cornerstone procedures of generating grinding and profile grinding is a key area of application. With generating grinding, for example, the gear geometry is continuously generated by a combination of multi-axes, high performance machine motions and well-maintained grinding wheels. EMAG SU’s G 160 model is a fast machine for components up to module 3 with a maximum outside diameter of 160 mm. The G 160 speed is made possible by an innovative slide axis concept with two parallel workpiece tables that take turns moving at high speed (with the help of durable, high performance linear motors) to the grinding wheel. During the time that one component is being machined, the loading robot inserts a blank into the other spindle, after first unloading the completed part, as needed. Self-centering alignment, or “meshing,” of the grinding wheel to the rough-cut gear component takes place directly on the workpiece spindle, at load position, in parallel with the main machining operation. This results in a chip-to-chip time between the grinding processes of only 1.6 seconds (a very small value compared to grinding machines with turntables, where in some cases up to five seconds pass for the same process). Here it is important to note that the actual grinding time needed for a typical component, such as a planetary gear wheel, is only about 10 seconds. The difference between the chip-to-chip times between grinding is therefore a real game changer. The floor-to-floor time is significantly reduced, by about three seconds (more than 20 percent), and the output quantity is massively increased. This is a decisive factor in the planning of high-volume manufacturing in the growing electromobility market.
G 250: short cycle times – maximum flexibility
Another interesting machine concept can be found in the G 250 machine of EMAG SU, which is suitable for components up to module 7, with an outside diameter of 250 mm. Axle drive gears, gear wheels or shafts with a maximum length of 550 mm can be produced with this solution, using generating grinding or profile grinding, with short cycle times. To this end, the machine is equipped with 2 table spindles to minimize idle time during the manufacturing process. “Additionally, the flexibility of the machine was very important to us,” said Morhard. “For example, the G 250 can also be equipped with very small grinding wheels and worms.” The G 250 HS variant also has a high-speed grinding head, which makes 20,000 rotations per minute possible, if a small grinding worm is used.
For large components in trucks or in general gear manufacturing, the cost-efficient G 400 rounds off the upper end of EMAG SU’s product range for generating grinding. It is equipped with a tool table for components with a max. diameter of 400 mm and a shaft length of up to 750 mm. A feature that is important to many users: The machine can also be loaded from above, because the housing has an over-the-corner door.
Increasingly strengthening the market by contributing strengths
Short chip-to-chip times, intelligent axis concepts, thermal and mechanical stability, as well as high “user-friendliness,” including self-explanatory, parametric input windows. With these quality characteristics, EMAG SU boosts the performance of tooth flank grinding procedures. To accommodate various grinding wheel sizes and types, a variety of spindles with the corresponding power and performance is available. Additionally, the technology can easily be combined with different automation technologies.
“We consider ourselves ideally equipped to supply machines for the grinding tasks needed in the field of electric mobility, as shown by a well-known French automotive manufacturer currently successfully using several EMAG SU grinding machines to generate gears,” said Morhard. “In the coming years, we want to continuously improve our contribution to the global requirement for precision gear grinding machines for the ever-increasing quality demands for electric vehicles.”