Workpiece locking system, comprising: a. two or more locking members to lock a workpiece; b. for each locking member, a support rod which extends vertically and carries a respective locking member, each support rod being vertically movable independently of the other support rods to make possible a vertical positioning of the respective locking member at a different vertical height compared to the other locking members; c. support means comprising two or more holes within each of which a respective support rod is movable vertically; d. for each support rod, stop means configured to lock the respective support rod in position with respect to said support means; e. at least one positioning table vertically movable with respect to said support means, said at least one positioning table being configured to interact in contact with said support rods to vertically move said support rods; f. actuator means configured to move said at least one positioning table; characterised in that said workpiece locking system further comprises: g. for each support rod, coupling means configured for removably coupling said at least one positioning table to said support rod so that said at least one positioning table drags said support rod downwards to overcome a frictional force between said support rod and the respective hole, said coupling means being configured to solve the coupling between said at least one positioning table and said support rod when said stop means locks said support rod and said at least one positioning table moves downwards away from said support rod, said stop means exerting on said support rod a stopping force greater than a coupling force between said at least one table and said support rod. a. two or more locking members to lock a workpiece; b. for each locking member, a support rod which extends vertically and carries a respective locking member, each support rod being vertically movable independently of the other support rods to make possible a vertical positioning of the respective locking member at a different vertical height compared to the other locking members; c. support means comprising two or more holes within each of which a respective support rod is movable vertically; d. for each support rod, stop means configured to lock the respective support rod in position with respect to said support means; e. at least one positioning table vertically movable with respect to said support means, said at least one positioning table being configured to interact in contact with said support rods to vertically move said support rods; f. actuator means configured to move said at least one positioning table; characterised in that said workpiece locking system further comprises: g. for each support rod, coupling means configured for removably coupling said at least one positioning table to said support rod so that said at least one positioning table drags said support rod downwards to overcome a frictional force between said support rod and the respective hole, said coupling means being configured to solve the coupling between said at least one positioning table and said support rod when said stop means locks said support rod and said at least one positioning table moves downwards away from said support rod, said stop means exerting on said support rod a stopping force greater than a coupling force between said at least one table and said support rod.