A cam and cam follower apparatus translates linear cam bar movement to perpendicular valve stem actuation in an injection molding system. The cam bars reciprocate up and down on linear bearing rails such that an actuation plate, fitted with a plurality of valve stems, is cycled normal to the direction of the cam bar movement via cam followers traveling within cam slots in the cam bars. The cam slots in the cam bars are profiled such that the cam followers affect the speed and force at which the valve stems travel while at the same time reducing frictional effects and their associated power requirement. The cam followers of the valve stem actuation plate travel in cam slots in the cam bars from a valve stem forward position, to a valve stem retracted position and ultimately, the entire actuation plate may be removed from the cam bars for maintenance via open ended slots in the cam bars.