Die Zone of Extruder: Melt Shaping and Structural Design

The die zone gives shape to the melt. It is mounted with an adapter ring. It is made of tool steel and usually chrome plated for production. The design of the die needs to ensure proper melt flow without stagnation regions, where material sits for long periods of time. The land is a short section at the exit orifice of the die where the walls are parallel. This builds uniform pressure in the melt and stabilizes the flow. The zone of maximum pressure in the extruder influences back pressure. If the land is too long, higher back pressures are generated causing reduced output and internal wear on the thrust bearing. If the land is too short, the melt flow is erratic and the part will be less uniform. Fig. 1 shows different types of extrusion dies.

Fig. 1