Robot Control from a Machine-tool CNC

One of the challenges of integrating robots and machine tools is that each has its own control system.

Robot Control from a Machine-tool CNC

One of the challenges of integrating robots and machine tools is that each has its own control system. Now, CNC developer Siemens (siemens.com) and robotics maker Comau (comau.com) have jointly engineered a control system that integrates robotic kinematics with a machine tool’s CNC. Sinumerik Run MyRobot/Direct Control lets both the machine tool and the Comau robot be programmed and controlled from a CNC operator panel.

The benefits go beyond the obvious one of being able to set aside the separate robot controller. Programming the robot is a simpler task in this arrangement as it uses an interface designed for machinists who don’t necessarily have experience with robots but know their way around a CNC.

More significantly, the CNC is a much more powerful piece of technology, of which much more is expected, than a robot controller. The latter is optimized for the fastest possible movements along unchanging paths, such as in assembly-line welding applications. If, however, robots are required to perform frequently changing movements, their controllers are generally not precise enough.

“This is due to the mathematics of robotic control algorithms, which are simplified and optimized for speed,” says Siemens engineer Rainer Adolf. CNCs use more complex mathematics.

For example, algorithms in some machine tool controls automatically optimize parameters such as machining rate or damping while taking account of friction and the contours of a workpiece—and they do so in advance, before the tool has moved. Now, with complete knowledge of the robot’s electronics and mechanics, these algorithms can also increase precision in setting up robotic movements, Adolf says.

Better control and precision enable the robot to do more than the usual loading/unloading tasks. For example, after a machine tool has milled a metal workpiece, a robot could not only unload it but also deburr it with a grinding tool attachment while the machine tool is milling the next workpiece. “A controller from a robot manufacturer could never carry out fine grinding work to a precision of fractions of a millimeter,” Adolf says, but this CNC can, empowering the robot to work more closely and effectively with the machine tool in this and other ways.