The application provides a molding apparatus. The molding apparatus comprises a first mold-defining member together with a second mold-defining member, one or more channels, and one or more moveable cores. The first mold-defining member together with the second mold-defining member defines an internal cavity. The channels comprise inlets for receiving molten resin and outlets to the internal cavity. The moveable cores are moveable between a first position and a second position, wherein the moveable core in the second position reduces a volume of the internal cavity and closes the channel outlets. The moveable core is also independently moveable with respect to the first mold-defining member and with respect to the second mold-defining member.