A drive system for an injection molding apparatus , said drive system having a longitudinal axis defining an axial direction and comprising: a stripper plate mounted for bilateral reciprocating motion, said stripper plate having a first face and a second face opposed thereto; a core pin protruding outwardly and forwardly through a hole in said stripper plate , said core pin being usable to form a cavity in a molded workpiece ; a core pin sleeve circumscribing said core pin and being juxtaposed with said first face of said stripper plate , said core pin sleeve having a feature to form an undercut in a molded workpiece removably disposed on said core pin ; a hollow stripper sleeve , said stripper sleeve being rigidly joined to said second face of said stripper plate , said stripper sleeve being concentric with said core pin and circumscribing said axis, said stripper sleeve having at least one stripper sleeve cam therein, said stripper sleeve cam providing for responsive motion of a respective stripper sleeve follower when said stripper plate is moved in an axial direction; a core pin base rigidly joined to said core pin and being disposed rearwardly of said second face of said stripper plate , said core pin base having at least one core pin base cam therein, said core pin base cam providing for responsive motion of a respective core pin base follower when said stripper plate is moved in an axial direction; a stripper sleeve insert intermediate said stripper sleeve and said core pin base ; said stripper sleeve insert having an outwardly extending stripper sleeve follower cooperating with said stripper sleeve cam and an inwardly extending core pin base follower cooperating with said core pin base cam , said stripper sleeve insert being rigidly joined to said core pin sleeve , whereby axial movement of said stripper plate causes motion of said stripper sleeve and said core pin base to be superimposed onto said stripper sleeve insert to cause responsive motion in said core pin sleeve . a stripper plate mounted for bilateral reciprocating motion, said stripper plate having a first face and a second face opposed thereto; a core pin protruding outwardly and forwardly through a hole in said stripper plate , said core pin being usable to form a cavity in a molded workpiece ; a core pin sleeve circumscribing said core pin and being juxtaposed with said first face of said stripper plate , said core pin sleeve having a feature to form an undercut in a molded workpiece removably disposed on said core pin ; a hollow stripper sleeve , said stripper sleeve being rigidly joined to said second face of said stripper plate , said stripper sleeve being concentric with said core pin and circumscribing said axis, said stripper sleeve having at least one stripper sleeve cam therein, said stripper sleeve cam providing for responsive motion of a respective stripper sleeve follower when said stripper plate is moved in an axial direction; a core pin base rigidly joined to said core pin and being disposed rearwardly of said second face of said stripper plate , said core pin base having at least one core pin base cam therein, said core pin base cam providing for responsive motion of a respective core pin base follower when said stripper plate is moved in an axial direction; a stripper sleeve insert intermediate said stripper sleeve and said core pin base ; said stripper sleeve insert having an outwardly extending stripper sleeve follower cooperating with said stripper sleeve cam and an inwardly extending core pin base follower cooperating with said core pin base cam , said stripper sleeve insert being rigidly joined to said core pin sleeve , whereby axial movement of said stripper plate causes motion of said stripper sleeve and said core pin base to be superimposed onto said stripper sleeve insert to cause responsive motion in said core pin sleeve . <EOS>