An independent, applied research institute, the Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM) in Stade, Germany, is changing the physics of machining – or to be specific, the kinematics of the process. “Kinematics” describes how objects or systems move without consideration of the forces that act upon them. It studies how things move, not why things move.
IFAM has developed a technology it states will improve the dynamics and precision of industrial robots, combining intelligent, model-based control with innovative drive technologies and an optimized mechanical structure for a robot.
The new Machine Tool Robot makes it possible to compensate dynamically for machining errors, and for machine vibrations to be effectively damped – which will mean significantly improved part accuracy, even with high feed rates and complex movements.
As such, the Machine Tool Robot “closes the gap between classic industrial robots and machine tools.”
Also, according to IFAM, the MTR optimizes “disturbance rejection,” which ensures constant precision even with highly dynamic process forces. This drive concept allows machining with higher material removal rates plus the ability to operate with higher jerk settings, both of which will increase productivity significantly.
It is particularly suitable for demanding manufacturing processes, e.g., machining of harder materials, and for incorporating new automation technologies, as well as smart industry application.
Alternative machine concept
Industrial robots permit operators to adopt alternative machine concepts, for example, extending the workspace by incorporating a surface-moving platform, or additional translatory axes, such as linear axes, or in combination with other robots.
Compared to gantry systems or machine tools, the MTR is a more space-saving machining concept, and does not depend on large components to be economically feasible.
Furthermore, it will not require special foundations, so it will be easier to adapt to production lines.
The combination of serial articulated-arm kinematics with a linear axis provides many advantages over large gantry and special machines for processing components. The smaller mounting space and the modular design of the linear axis make the MTR system highly flexible.
The use of two, preloaded rack-and-pinion drives compensates for reversal effects and achieves a sufficiently high drive stiffness of the linear axis carriage for path-accurate robot processes.
Due to the high structural rigidity of the linear axis, the influences on the robot accuracy are low despite the large lever arms to the load application point.
A software application for model-based calibration called CaliRob (and also developed at Fraunhofer IFAM) opens up a complementary technology for increasing precision: Due to unavoidable manufacturing tolerances, industrial robots exhibit individual deviations from the ideal system. These deviations may result in errors of up to several millimeters when approaching target positions in robot systems without knowledge of these deviations. In order to achieve the highest possible accuracies, industrial robots must therefore be calibrated according to requirements, for example with CaliRob. A key element of this application is a very extensive mathematical model that includes over 200 parameters to describe robot kinematics on a linear axis.
Future possibilities
In the next step, the experts at Fraunhofer IFAM will test the new robot system together with their R&D partners autonox Robotics GmbH as well as Siemens AG in demanding industrial applications in order to further advance the potential of the technologies.
Machine Tool Robots can be used for various applications: In combination with a linear axis, this will range from aerospace machining (e.g., lighter fiber composite structures and aluminum alloys) to machining of harder materials (e.g., steel or titanium for rail, commercial vehicle, shipbuilding, as well as in energy sector projects. Until now, it has not been possible to machine such components and materials in an industrially robust manner using industrial robots. Now, in particular for the machining of harder materials, using Machine Tool Robots presents many new possibilities.