A clamping assembly for an injection molding apparatus includes a first platen attached to a base and a second platen slidingly associated with the base. A number of tiebars are mechanically linked to each of the platens through a number of mechanical linkages. An actuation system associated with the plurality of tiebars and with at least one of the platens is configured to generate movement of the second platen relative to the first platen. The mechanical linkage between each of the tiebars and at least one of the platens includes a threaded bushing engaged with a threaded portion of the tiebar. The actuation system is configured to generate relative rotation between each of the tiebars and a corresponding one of the threaded bushings.