Drive Drive Technology for XL-Format Machining Centers

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Stöber Antriebstechnik GmbH & Co. KG

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With the twin-spindle high-performance machining centers BA Space 3 from Schwäbische Werkzeugmaschinen GmbH, customers can manufacture components up to three meters long—for example, battery housings for electromobility. Stöber supplies robust and compact servo gear units for the drives of the swivel carriers, among other components.

The heart of an electric car is the battery. However, in the event of an accident, it can pose a significant hazard. The safety concept includes, among other things, the battery tray on the underside of the vehicle, where the cells are installed. It is typically integrated directly into the load-bearing structure, thereby increasing the overall stability of the vehicle. "These workpieces are large lightweight metal components or blocks of aluminum that are machined on a machining center," reports Cristina Fernández. She is a Strategic Buyer at Schwäbische Werkzeugmaschinen GmbH, or SW for short, in Schramberg-Waldmössingen, Baden-Württemberg (Germany).

Users can also machine components cast in one piece on our system. This enables us to offer solutions for the underbody, the subframe, and especially for battery housings.

Cristina Fernández, Strategic buyer at SW

CNC Machining Centers With Modular Automation

With around 1,700 employees, SW develops smart manufacturing solutions such as CNC machining centers with modular automation, autonomous manufacturing cells, and complete manufacturing systems with integrated software solutions. In addition to electromobility, the machines are used in industries such as automotive, aerospace, and agricultural and construction machinery.

For the production of large-volume workpieces, the four-, optionally five-axis machining center of the BA Space 3 series is suitable. It is one of the large machine series found in the SW portfolio. "Users can also machine components cast in one piece on this system," describes Cristina Fernández. "This allows us to offer solutions for the underbody, the subframe, and especially for battery housings."

Drive With Special Requirements Sought

The machine's working area measures 118 × 71 × 34 inches. As large as the workpieces to be manufactured are, they are equally heavy. The rotary axis of the swivel carrier, which handles the positioning unit and workpiece holder, must be capable of dynamic movement. For the new BA Space 3, for example, the drive needs to transmit high torque, and the gearbox must be able to accommodate increased tilting moments. "Our goal was to avoid installing an additional radial bearing," says Cristina Fernández.

A servo motor from Siemens is being used. For the other drive components, such as suitable gearboxes, SW's decision-makers considered various suppliers. They ultimately chose Stöber from Pforzheim. The gearboxes from this drive specialist can not only be directly combined with the company's own motors but also with all third-party motors of any size via a unique interface technology—designed to be ready for connection with any system. What was decisive in the end was the good price-performance ratio, which allowed Stöber to stand out from the competition. "As a partner, we supported Schwäbische Werkzeugmaschinen GmbH throughout the entire project," says Alexander Schmidt, Area Sales Manager at Stöber.

Electric Drive Technology

Why Multiphysics is Becoming Increasingly Important

Maximum Torque With Three-Stage Servo Gearbox

"For the servo motor, we supplied a precise three-stage servo gearbox of the PHQ10 series with high-quality helical gearing and very high torsional and tilting rigidity—initially in the third, now in the fourth generation," reports Schmidt.

This ensures maximum torque from the drive specialist. The "Q" in the name stands for Quattro Power. The 4-planet system is particularly suitable for drives in pick-and-place applications. Another advantage: appropriate bearings are available depending on the application. This allowed the specialists from Pforzheim to precisely combine the drive solution and the gear ratio. The PHQ10 is a powerhouse that is very rigid and low-backlash, capable of transmitting high external forces. To lock the rotary axis during machining, Stöber also supplied face gear rings. The design was developed in collaboration with SW's engineering team.

While the machine operates, the system can already be loaded from the outside.

Cristina Fernández, Strategic buyer at SW

Customers benefit from the new machining center's high output of parts, significantly enhancing their competitiveness. This is partly due to the linear motors in the feed axis, which achieve high dynamics, and partly due to reduced downtime. Since the workpiece carrier swivels around the rotary axis, parallel loading during main operation is possible. "While the machine works, the system can already be loaded from the outside," says Cristina Fernández.

Up to 25 Years of Trouble-Free Operation

"We worked very harmoniously and always in close coordination with each other," concludes Fernández. Stöber was involved in the project planning from the very beginning. What ultimately convinced them were the high-quality drive components, which offer great durability and time efficiency. "A machine can be in operation for 20 to 25 years, and the drives must be able to function reliably and without issues throughout that time," says Schmidt from Stöber. This was complemented by competent engineering and the design of the gearboxes. The commissioning also went smoothly and was completed in a short time.

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