control can also be provided wherein the pressure on the valve is profiled such that the position of the spool valve dynamically changes to provide a proportional pressure at the tip of the extended valve pin closed loop control can also be used wherein the location of the spool valve and or the melt pressure at varying locations and or the load on the spool valve are observed and utilized to change the position of the spool valve to alter the volumetric flow rate or pressure at the spool valve the spool valve can preferably be moved through a variety of designs including electric pneumatic hydraulic screws gears and other power transmission elements as discussed the spool valve has minimal actuation forces required for control and the forces acting on the system will be dominated by the melt pressure acting on the pin tip used for closure of the valve gate 18 preferably actuators can rapidly actuate the spool valve valve pin and also hold position without consuming excessive power such exemplary actuators include a ball screw rotated by an electric or pneumatic motor and a hydraulic cylinder there are several benefits to using an electric motor which offsets its disadvantages which include high cost low operating temperature and low power density first the electric motor avoids the use of fragile and costly pneumatic or hydraulic hoses second the.