Abstract: A robot or other manipulator has an end effector useful for gripping a part and performing an assembly operation to a second part, the assembly requiring, for example, an insertion and a rotation motion. A sensor is mounted between the manipulator and the end effector and comprises a pair of telescoping sections mounted for relative axial and rotational movement with springs for normally inhibiting any movement beyond a range caused by normal assembly forces. An excessive force caused by the failure of the parts to join normally results in a relative axial or rotational movement which is sensed by one or more cam operated switches. The switches are arranged to yield a plurality of signals which contain coded information on the specific type of overload movement. The information can be used by a robot or manipulator controller to stop the assembly operation and then to make the appropriate movements to solve the problem or to simply indicate to an operator the type of malfunction.