WORKPIECE CONDITIONING GRINDER CONTROL SYSTEM

TITLE WORKPIECE CONDITIONING GRINDER SYSTEM An elongated metal workpiece such as a slab or billet is moved longitudinally beneath a grinding head by a reciprocating car mounted on an elongated track. The car receives a billet from a charging table or other loading device, reciprocates the billet beneath the grinding head for a plurality of grinding passes, and then delivers the finished billet to a discharge table. The grinder head includes a rotating grinding wheel mounted at the end of a first arm which is pivotally secured to one end of a pivotally mounted second arm. A hydraulic actuator extending between the frame and the first arm controls the grinding force exerted by the grinding wheel on the workpiece. One end of the actuator is connected to an accumulator which provides a constant upward bias to the arm while the pressure in the other end of the actuator is varied in accordance with a pressure control signal. The pressure control signal is derived from both a calculated torque command indicative of the grinding force expected to produce a grinding torque corresponding to the torque command and a torque error signal which is a function of the deviation of actual torque from the torque command in order to maintain the grinding torque substantially constant. The car may be reciprocated so that the grinding wheel travels beyond the end of the workpiece with the hydraulic actuator being locked to hold the position of the wheel constant. The grinding force may be limited to a preset maximum by allowing hydraulic fluid to flow from the actuator to raise the grinder head as grinding force exceeds the limiting value. Grinding wheel vibration is limited by clamping the second arm to a massive, rigid foundation during each grinding pass thereby limiting the movement of the grinding head to a single degree of freedom. The grinder system may be operated in either a manual spotting mode in which the positions of both the car and grinder head are manually controlled but maximum grinding torque is limited, a manual skinning mode in which the position of the car is manually controlled but the grinding force exerted by the grinding wheel on the workpiece is automatically adjusted to maintain the grinding torque proportional to car speed but no more than a preset maximum, and an automatic skinning mode in which the car automatically reciprocates between the ends of the workpiece and the grinding force is automatically adjusted to maintain the grinding torque propor