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Twin Screw Extruder Dies and Die Assemblies: Downstream Tooling
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Various equipment options are available for the tooling which attaches to the last barrel of the Extruder/Compounder. These options range from an 8-0, which converts the Figure 8 of the barrel to a single output “0” (used as the supply for a screen changer, gear pump, or underwater pelletizer) to a multistrand Die Head Assembly which converts the product flow into strands which are cut to the correct length with a strand pellitizer.
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The 8-0 can be provided in two configurations. The first configuration is a single piece 8-0 which bolts to the end barrel and connects directly to the downstream equipment. The second configuration is more popular as it consists of two pieces clamped together which allow the 8-0 to open for removal of the screw shaft assemblies from the extruder.
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There are several variations of multistrand die heads for use on extruders. The standard die head accepts the Figure 8 flow path from the extruder and it converts this flow into a horizontal slot which directs the flow to a discharge angle 45° from vertical. This orientation allows the flow from the die head to be discharged into a water bath with minimal breakage of strands. Die plates are available with various combinations of hole diameters and number of holes.
The most common multistrand die head includes a hinge assembly which allows the die head to separate from the die adapter plate to provide access to the screw shaft assemblies. This die head assembly is supplied with a die adapter plate which bolts to the discharge barrel and facilitates the installation of the stationary portion of the hinge. The hinge bracket can be assembled to either side of the die adapter plate which allows the die head to open to the left or to the right.
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Cartridge heaters are used with the 25 and 30 mm die heads and are installed in the die body. Cast bronze plate heaters are used with the 40 mm through 92 mm die heads and they apply heat to the front and sides of the die body.
All die heads are designed to accept breaker plates that are capable of accepting screen packs for filtering foreign materials from the product flow.
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