Co-injection hot runner nozzle

A co-injection molding method comprising:

• splitting a first melt flow between an inner channel and an outer channel of a co-injection hot runner nozzle, the outer channel forming an annular outer melt flow that surrounds an inner melt flow formed by the inner channel;
• and
• splitting a second melt flow among a plurality of feeder channels upstream of an annular intermediate channel of the co-injection hot runner nozzle, the intermediate channel being disposed between the inner and outer channels and being at least partly defined by a plurality of spiral grooves, each spiral groove having a respective inlet, the plurality of feeder channels supplying melt to the inlets of the plurality of spiral grooves, the intermediate channel being further defined by lands between adjacent spiral grooves that increase in clearance in a downstream direction, wherein melt comprising the second melt flow travels along helical paths defined by the respective spiral grooves and spills over the lands to form an annular axial flow, wherein the forming of the annular outer melt flow comprises passing melt through a plurality of flow transition channels arranged in a ring, each of the flow transition channels having an inlet, an outlet with a part-annulus shape, and a pair of opposing side walls that diverges in the downstream direction.