To find out which applications could benefit from improved robot technology, Siemens conducted a comprehensive market analysis together with the Fraunhofer Institutes in 2019. In addition to machining processes such as laser cutting and build-up welding, the focus was primarily on precision milling. What was missing for a broad-based, successful application was the achievable accuracy. A challenge that has now been solved.

The combination of mobility, flexibility and precision opens up fields of application (see box) that were previously uneconomical or technically impossible to implement. Whether mobile maintenance, large-scale machining or flexible production cells, the new generation of milling robots with specially developed spindle technology is ready to fundamentally change production processes.

But how and why is this now possible? The basis lies in the greatly improved kinematics, the powerful drive motors and the intelligent control technology of the patented Sinumerik Machine Tool Robot (MTR) concept. Milling robots with MTR technology now achieve ten times greater precision than conventional industrial robots. This means that they work in the sub-millimeter range, setting new standards for robot-assisted machining. However, there is another key component that is crucial to achieving this level of precision on workpieces: the milling spindle. Weiss Spindeltechnologie, a specialist division of Innomotics, has succeeded in developing and building it.

Lightness of the spindle is crucial

According to Weiss project manager Georg Sauer, the challenges were many and varied. It was particularly important to build the spindle as light as possible while still achieving maximum stability and performance. The engineer explains: "In contrast to stationary machine tools, every kilogram plays a decisive role in robot applications, as the spindle is located at the end of the arm, where the weight is multiplied." Accordingly, consistent lightweight construction was the order of the day. This was achieved by adapting the design and optimizing the choice of materials.