A method for avoiding an unwanted collision between a tool and a workpiece in a machine tool is disclosed, wherein when a parts program starts to run, the determination of setpoint movement values for controlling a relative movement between tool and workpiece is started based on the parts program and a determination of the material removal at the workpiece by the tool is started based on the determined setpoint movement values. It is then checked whether a tool model overlaps with a workpiece model. When an overlap is detected, the relative movement between tool and workpiece is slowed down until the relative movement stops. A related facility employing the method for controlling a machine tool is also disclosed. Unwanted collisions between a tool and a workpiece in a machine tool can thus be avoided, while attaining short machining times for the workpiece.