Automotive manufacturers produce small to medium-sized components in large to very large quantities in transfer centers. In order to be able to map all processing steps for a series, manufacturers often require several processing machines that are coupled in series. The reason for this is that spindles are often used that all have to be driven individually. As a result, it is often not possible to integrate the required number of spindles for simultaneous complete machining of several components into one machine in a sensible and collision-free manner. This has an impact on the quality and speed of the production process: if several machines are required to manufacture the workpieces, the blanks have to be reclamped several times, which results in a loss of time and accuracy. In automotive production, which has to meet the highest quality standards, efficiency requirements are increasing significantly. Machine manufacturers are therefore called upon to offer the industry alternatives to conventional machining centers.

Four direct drives for 32 tools

In collaboration with Elha-Maschinenbau, Sauter Feinmechanik has developed the first spindle row turret. The machine has the typical characteristics of a direct-drive tool turret, is gearless, wear-resistant and can be kept in continuous operation 24 hours a day, seven days a week. In addition, the spindle row turret has several working positions connected in series: two to four spindle rows, each of which is set in motion by a water-cooled direct drive. This allows up to four tools to be driven simultaneously - one per row. Eight tools are available in each spindle row for machining a workpiece. As soon as a machining step is completed, the spindle row turret swings to the next position within 0.8 seconds and a new tool is used in each row.

Currently, up to four spindle row turrets, each with four spindle rows and a total of 128 tools, can be integrated into one transfer center. This means that up to 32 machining steps per workpiece can be realized in just one machine without retooling. The reason for this high level of flexibility is that, while individual spindles require a drive for each spindle, eight tools are driven by a direct drive in the spindle row turret. "In addition to the quick changeover from one working position to the next, the large number of different tools is one of the major advantages of our spindle row turret. This means that the workpiece never has to be reclamped. This gives users a significant boost in productivity and increases the quality of their components at the same time," says Matthias Beck, Head of Design Tool Carrier Systems at Sauter.

High speeds and torques

Currently, up to four spindle row turrets with a total of 128 tools can be integrated into a transfer center. © Elha mechanical engineering

Not only the change between the machining steps, but also the duration of the individual processes is significantly accelerated by the spindle row turret. This is mainly due to the highly dynamic synchronous motors in the tool disks, which enable high speeds and torques. Users thus maximize their metal removal rates and massively reduce their workpiece times. To exploit this potential, Sauter has developed new safety systems: Before all four direct drives are engaged simultaneously, a three-part Hirth coupling locks the tool disks with micrometer precision and the desired tools are in the working position. This coupling profile ensures maximum process stability, enabling torques of up to 250 Nm to be achieved.

As soon as machining begins, the internal coolant supply with a pressure of 80 bar conveys coolant through the direct drive and the tooling to the tool cutting edges. If required, the spindle row turret can also be converted to minimum quantity lubrication. In this case, an aerosol is transported through the tool to the tool disk. As no cooling lubricant is used, minimum quantity lubrication is more environmentally friendly than conventional cooling.