29.07.2025

Stator machining solution ready for series production

NILES-SIMMONS and MAPAL set new standards

A process for the complete machining of stator housings for electric motors developed by the Chemnitz machinery manufacturer NILES-SIMMONS and tool manufacturer MAPAL has made it to series production.

Daniel Pilz, André Ranke, and Thomas Lötzsch present a sample component, a fine boring tool, and a customer component.

Both manufacturers recently proved in a development project that highly cost-efficient and precise production of stator housings is possible on a pick-up lathe. The thin-walled aluminium components are required for the drive in electric vehicles. They are ribbed on the outside for the cooling circuit and are installed in the larger motor housing.

Image of the workpiece mounted in the turning machine — The workpiece is taken to the different machining stations one after the other in the pick-up turning machine. ©MAPAL

The bell-shaped outer tool stands still. The component is placed in the gap between the inner and outer tool for machining. This patented process reduces forces that occur on the clamping system. This makes it possible to avoid using a complex workpiece clamping device with vibration damping for precise machining of the thin-walled components. “When designing the tool, particular attention was paid to the large chip volume and the significant forces generated, as it is unusual for the inner and outer diameters to be machined simultaneously”, explains Michael Kucher, Component Manager E-Mobility at MAPAL.

During finishing, only the fine boring tool is driven, while the component stands still. This prevents workpiece shapes that are not rotationally symmetrical from causing imbalances in the material and having a negative impact. The workpiece is then reclamped in the machine and the outer area that was previously clamped in the flange area is machined. The re-clamping station can also be used for another purpose: the workpiece is placed here before fine boring to relax the material. The machine has two tool revolvers for driven tools that carry out further machining based on component requirements.

Faster and more stable than expected

“The bottom line is that the RASOMA DZS 400-2 brings together the best of both worlds: the turning speed for pre-machining inner and outer contour with the accuracy of fine boring for finishing the inner contour”, says Daniel Pilz, Project Leader at NSH TECHNOLOGY. The machine tool manufacturer and MAPAL contributed their respective core competences to this complete solution. With the serialisation of the machine, tool technology and process, the positive results of the prototype were improved even further. The process reliability achieved even exceeded expectations, allowing the targeted cutting speed of 700 m/min to be increased even further. “For this aluminium machining, the experience NILES-SIMMONS brings from the diversity of technology has a positive impact on the overall reliability of the tool technology and machine”, explains Michael Kucher, Component Manager E-Mobility at MAPAL.

The RASOMA DZS 400-2 achieves a much shorter chip-to-chip time than a milling centre. This is because all tools are already in the working area and are only brought into working position by swivelling the revolver disc. This does away with all tool changes, reducing non-productive time substantially. Using this technology, a cycle time reduction of 50% versus standard turning was already anticipated in studies. During process optimisation, cutting speeds of 1,000 m/min were achieved using optimal cutting material. The additional optimisation of non-productive time resulted in even more time saving of 20%.

View highlighting the critical dimensions during the machining process of the workpiece — The difference in the tool speed and the workpiece speed produces the cutting speed at the inner blades. The bell-shaped outer tool stands still. ©MAPAL

The process is so reliable that random sampling is sufficient for quality assurance. While all manufactured components were measured at first, the current recommendation is just one part per shift. Daniel Pilz uses figures to demonstrate that this is more than satisfactory: “The RASOMA DZS 400-2 with the special tools from MAPAL achieves a process capability index of over 1.67 for critical characteristics, such as cylinder shape, diameter and concentricity and thus meets industrial specifications.” Customers for whom the machine is already in use achieve an annual output of up to 180,000 components produced in three-shift operation.