An injection molding arrangement comprising a mold top clamp plate having a means for receiving a plasticizer unit; a manifold retainer plate supporting a heated melt distribution manifold having a melt distribution channel into which melt from said plasticizer unit is received; a mold cavity plate provided such that said manifold retainer plate is positioned between said mold top clamp plate and said mold cavity plate; said mold cavity plate receiving an injection nozzle in fluid communication with said melt distribution channel for receiving melt to be injected into a mold; a valve gate stem extending into said injection nozzle and axially movable between an open position permitting melt flow and a closed position blocking melt flow; an actuator for moving said valve gate stem between said open position and said closed position; said actuator including a cylinder chamber receiving a piston therein; said valve gate stem coupled to said piston; and said piston having an elongate cylindrical sidewall; wherein said cylinder chamber and said piston are sized and otherwise dimensioned to provide a microgap seal along said uninterrupted elongate cylindrical sidewall between an upper chamber of said cylinder chamber and a lower chamber of said cylinder chamber; wherein the microgap seal is between 1 and 10 microns in width, and more preferably about between 4 and 6 microns, for having a leak of less than about 100 ml/min, when being used with an operating pressure of 5 - 10 bar; wherein said cylinder chamber is provided in a chamber housing having a closed top end and an open bottom end; and further comprising a housing cap for enclosing said bottom end thereby defining said lower chamber between said housing cap and a bottom surface of said piston; said housing cap having a valve bore for which said valve gate stem can pass through; characterised by further comprising a stand-off between said bottom end of said housing and said housing cap; said housing cap including a boss portion extending into an interior of said stand-off; and further comprising a second microgap seal between an interior surface of said stand-off and said boss portion. a mold top clamp plate having a means for receiving a plasticizer unit; a manifold retainer plate supporting a heated melt distribution manifold having a melt distribution channel into which melt from said plasticizer unit is received; a mold cavity plate provided such that said manifold retainer plate is positioned between said mold top clamp plate and said mold cavity plate; said mold cavity plate receiving an injection nozzle in fluid communication with said melt distribution channel for receiving melt to be injected into a mold; a valve gate stem extending into said injection nozzle and axially movable between an open position permitting melt flow and a closed position blocking melt flow; an actuator for moving said valve gate stem between said open position and said closed position; said actuator including a cylinder chamber receiving a piston therein; said valve gate stem coupled to said piston; and said piston having an elongate cylindrical sidewall; wherein said cylinder chamber and said piston are sized and otherwise dimensioned to provide a microgap seal along said uninterrupted elongate cylindrical sidewall between an upper chamber of said cylinder chamber and a lower chamber of said cylinder chamber; wherein the microgap seal is between 1 and 10 microns in width, and more preferably about between 4 and 6 microns, for having a leak of less than about 100 ml/min, when being used with an operating pressure of 5 - 10 bar;