a method and apparatus for injection molding articles from a thermoplastic or similar material . a plurality of molds are mounted on a turntable and are indexed to selected positions as the turntable rotates about its axis of rotation . radial slots divide the turntable into sectors , each having a mold thereon . a clamping mechanism is provided which successively deflects each sector slightly from the plane of the turntable in order to precisely align the mold thereon with an injection nozzle and then securely clamps the halves of the mold together while the injection nozzle injects moldable material into the cavity in the mold . interchangeable cavities with different size and shape characteristics are provided in the injection molds and associated with each mold is a resettable indicator designating the particular type of cavity presently installed in that mold . a sensor unit responsive to the indicators provides a control unit with an indication of the characteristics of the cavity in each mold when it is aligned with the injection nozzle and the control unit adjusts the parameters of the injection operation to correspond to those characteristics . in one embodiment , two injection nozzles are provided and an annulus is inserted into each mold cavity to separate the cavity into two portions , each of the nozzles injecting moldable material into a respective one of the cavity portions .