Long service life components

The heart of an e-vehicle is the battery. However, if an accident occurs, the battery can pose a significant danger. Addressing this requires a safety concept that includes the battery carrier on the underside of the vehicle where the cells are installed. It is usually integrated directly into the load-bearing structure, increasing overall vehicle stability.

“These workpieces are large, moulded parts that are made of light metal or from aluminum blocks and are milled on a machining center,” explains Cristina Fernández, strategic purchaser at Schwäbische Werkzeugmaschinen (SW for short). With around 1700 employees, SW develops smart manufacturing solutions, such as CNC machining centres with modular automation, self-sufficient manufacturing cells and complete manufacturing systems with linked software solutions. In addition to electromobility, the machines are used in industries such as automotive, aerospace, and agricultural and construction machinery.

The four-axis, or optionally five-axis, machining center from the BA space3 series is ideal for manufacturing large-volume workpieces. It is one of the large machine series in the SW portfolio.

“With this system, users can also process components cast in one piece,” explains Fernández. “Thus we can offer solutions for the underbody, the subframe and, above all, the battery housings.”

Seeking a drive with special requirements The machine has a workspace of 3000 × 1800 × 875mm. Since the workpieces being manufactured are large, they are heavy too. The rotary axis of the swivel carrier, which accommodates the positioning unit and workpiece holder, needs to be able to move dynamically. For example, for the new BA space3, the drive needs to be able to transmit high torque, and the gearbox has to absorb higher breakdown torque. “Our goal was to avoid installing another radial bearing,” says Fernández.

A servo motor from Siemens is used. To source the other drive components, such as appropriate gearboxes, SW managers considered various suppliers. They chose STOBER from Pforzheim. This drive specialist’s high-quality gearboxes can be combined with the company’s own motors in direct mounting, as well as with all third-party motors in any size, thanks to the unique interface technology – designed to be ready for connection to any system. In the end, the decisive factor that set STOBER apart from the competition was the excellent price-performance ratio.

“As a partner, we supported Schwäbische Werkzeugmaschinen throughout the entire project,” says Alexander Schmidt, area sales manager at STOBER. “For the servo motor, we supplied a precise three-stage servo gearbox from the PHQ10 series with high-quality helical gearing and very high torsional and tilting stiffness – initially a third-generation product, now in its fourth generation.”

This is how the drive specialist provides maximum torque. The “Q” in the name stands for Quattro Power. The system, featuring four planetary gears, is especially suitable for drives in pick-and-place applications. Another advantage is a selection that includes the right bearings for the specific application. This enabled the specialists from Pforzheim to precisely tailor the combination of drive solution and gear ratio. The PHQ10 is a very rigid, low-backlash powerhouse, capable of transmitting even high external forces. STOBER also supplied flat gear rings to lock the rotary axis during machining. The design process was carried out together with SW’s development team.

With the new machining center, customers benefit from high part throughput, enabling them to significantly increase their competitiveness. This is due to both the dynamic linear motors in the feed axis, which achieve high dynamics, and the reduced downtimes. Because the workpiece carrier swivels around the rotary axis, loading can be carried out in parallel with machining. 

“We had a very harmonious collaboration involving close coordination,” says Fernández. STOBER was involved in the project configuration process from the beginning. In the end, the high-quality drive components, offering high durability and fatigue strength, were persuasive selling points.

“A machine can be in operation for 20 to 25 years, so the drives need to be able to perform consistently without failure,” says Schmidt from STOBER. The final selling points were the expert engineering and gearbox design. Commissioning also went smoothly without any problems and was completed in a short time. 

www.stober.co.uk