A method of molding a workpiece having an undercut from a complementary core in an injection molding apparatus , having a longitudinal axis, said method comprising the steps of: providing an injection molding apparatus drive system comprising a stripper plate reciprocatingly drivable back and forth in an axial direction and having a core pin protruding outwardly from said stripper plate , said core pin being usable to form a cavity in a molded workpiece , a core pin sleeve juxtaposed with said stripper plate , said core pin sleeve having a feature to form an undercut in a molded workpiece , a hollow stripper sleeve , rigidly joined to said stripper plate and axially spaced from said core pin and circumscribing said axis, said stripper sleeve having at least one stripper sleeve cam therein providing for motion of a respective stripper sleeve follower , a core pin base rigidly joined to said core pin , said core pin base having at least one core pin base cam therein providing for motion of a respective core pin base follower , a stripper sleeve insert intermediate said stripper sleeve and said core pin base and being rigidly joined to said core pin sleeve , 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 ; injection molding a workpiece having a cavity onto said core pin and onto said core pin sleeve whereby said workpiece has an undercut formed by said feature of said core pin sleeve ; moving said stripper plate in an axial direction, whereby said stripper sleeve and said core pin base move with said stripper plate , so that said stripper sleeve follower and said core pin base follower superimpose respective motions thereof onto said stripper sleeve insert ; and synchronously moving said core pin sleeve and said stripper sleeve insert in said axial direction and a circumferential direction to thereby release said workpiece from said core pin sleeve and said core pin . providing an injection molding apparatus drive system comprising a stripper plate reciprocatingly drivable back and forth in an axial direction and having a core pin protruding outwardly from said stripper plate , said core pin being usable to form a cavity in a molded workpiece , a core pin sleeve juxtaposed with said stripper plate , said core pin sleeve having a feature to form an undercut in a molded workpiece , a hollow stripper sleeve , rigidly joined to said stripper plate and axially spaced from said core pin and circumscribing said axis, said stripper sleeve having at least one stripper sleeve cam therein providing for motion of a respective stripper sleeve follower , a core pin base rigidly joined to said core pin , said core pin base having at least one core pin base cam therein providing for motion of a respective core pin base follower , a stripper sleeve insert intermediate said stripper sleeve and said core pin base and being rigidly joined to said core pin sleeve , 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 ; injection molding a workpiece having a cavity onto said core pin and onto said core pin sleeve whereby said workpiece has an undercut formed by said feature of said core pin sleeve ; moving said stripper plate in an axial direction, whereby said stripper sleeve and said core pin base move with said stripper plate , so that said stripper sleeve follower and said core pin base follower superimpose respective motions thereof onto said stripper sleeve insert ; and synchronously moving said core pin sleeve and said stripper sleeve insert in said axial direction and a circumferential direction to thereby release said workpiece from said core pin sleeve and said core pin . <EOS>