Barrel feed housing

Barrel feed housing Component of the plasticator barrel that contains the feed opening, water heating and/or cooling channels, and in certain units, contains barrel grooving to improve flow of plastics into the screw flights. If required a thermal barrier is used that is attached to the barrel. 

Injection molding barrels are shorter than extruder barrels. The typical L to D ratio is 22 1 to 26 1 for fast-running machines and 28 1 for vented barrel injection machines. Unlike extruder barrels, the feed port is cut through the barrel and connects with water-cooled feed housing. The discharge end of the barrel fastens directly to the end cap or nozzle adapter, the counter bore at the end of the barrel centers the end cap. 

Since these benefits appeal to most extrusion processors, grooved barrel sections have become quite popular. Also, the use of grooved barrel sections allows processors to extrude materials that cannot be processed on conventional extruders, e.g., very high molecular weight poiyethyienes and powders. A grooved feed housing is shown in Fig. 7.18. 

The Feed Housing. The feed housing is connected to the barrel it contains the feed opening through which the plastic material is introduced to the extruder. The feed throat usually has water-cooling capability because the feed... 

To assist dispersion of colorant in the polymer melt the use of screw back pressure is recommended. The barrel temperatures at the hopper zone should be set lower than that at the nozzle to allow for additional mixing to take place within the feed section of the screw. PS is also sold as color compounded material and a color matching service is available but many processors purchase natural (clear) polymer and color in-house. 

Extruder Barrel n (extruder cylinder) A thick-walled, cylindrical steel tube, lined with a special hard alloy to resist wear that forms the housing for the extruder screw and contains, between itself and the screw, the plastic material as it is conveyed from feed hopper to die. Barrels are usually surrounded by heating and cooling media, such as electrical heater bands, cast-in-aluminum calrods and tubing for coolant, induction heaters, or, rarely, by a compartmented jacket for the... 

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