Injection unit for injection molding of plastic material including: an injection nozzle; a closure pin; and a guide and cooling assembly, interposed between the back driving plate and the hot distribution plate, in turn comprising: a guide and seal element for guiding the axial motion of the closure pin; a cooling ring; and pressure means configured to press the cooling ring directly and against the back driving plate; wherein the guide and seal element is slidably coupled, at an upper end, with a central hole of the cooling ring, and is fixed integrally, at the other end, to the hot distribution plate; and the cooling ring is able to slide laterally with respect to the back driving plate to recover the differences in thermal expansion between the hot distribution plate and the back driving plate and to transmit heat from the guide and seal element towards the back driving plate.

Injection unit for injection molding of plastic material including: an injection nozzle; a closure pin; and a guide and cooling assembly, interposed between the back driving plate and the hot distribution plate, in turn comprising: a guide and seal element for guiding the axial motion of the closure pin; a cooling ring; and pressure means configured to press the cooling ring directly and against the back driving plate; wherein the guide and seal element is slidably coupled, at an upper end, with a central hole of the cooling ring, and is fixed integrally, at the other end, to the hot distribution plate; and the cooling ring is able to slide laterally with respect to the back driving plate to recover the differences in thermal expansion between the hot distribution plate and the back driving plate and to transmit heat from the guide and seal element towards the back driving plate.

Disclosed is a method of manufacturing a manifold for use in plastic injection molding, the method comprising additive manufacturing a melt distribution structure onto a manifold base plate, wherein the manifold base plate comprises a critical assembly feature.

A mold assembly including a spacer positioned or disposed between a back-up plate and a cavity block, the mold assembly, and a method of coupling the back-up plate and the cavity block of the mold assembly using a fastener including the spacer substantially as described above, in order to provide spring-loaded self-adjusting alignment between mating mold inserts.

A sprue bush that is attached to a mold used to mold synthetic resin includes: a sprue bush main body (10) that has a flow passage, through which synthetic resin injected from an injection molding nozzle flows, and a recessed portion (13) formed in a surface of the sprue bush main body on a synthetic resin injection port side thereof; and a bush component (20) that is embedded in the recessed portion (13), the bush component (20) including: a nozzle contact surface (21) that is contacted by the injection molding nozzle; a through hole (22) that extends from an opening in the nozzle contact surface (21) and communicates with the flow passage in the sprue bush main body so as to form the flow passage for the synthetic resin; and a plurality of ribs (23) that extend radially outward from an inner peripheral surface of the through hole.