Barrel grooved feed

Barrel grooved feed Grooves in the internal barrel surface in the feed section, particular for certain materials, permits considerable more friction between the solid plastic particles and the barrel surface. Result is process output increases and/or the process stability improves. 

Table 5.3 Approximate Feed Channel Depths and Barrel Groove Dimensions as a Function of Barrel Diameters [49]...

Wortberg, J., Screw and Barrel Design for Grooved Feed vs Smooth Bore Extruders, SPEANTEC Tech. Papers, 48, 80 (2002)... 

By maximizing feed/barrel friction and minimizing feed/screw friction, solids conveyance is maximized. Typically, a threefold increase in extruder output is obtained using a grooved feed throat instead of a smooth one at the same screw speed. 

In addition to increased output, grooved feed throats have a couple of other benefits. A decrease in output variation (i.e., less surging) often results from creating high barrel friction. This is because of a decreased sensitivity to fluctuations in two common variables ... 

If the actual solids conveying performance is as sensitive to the coefficient of friction as the theory indicates, small changes in the actual coefficient of friction can have a substantial effect on the entire extrusion process. This is particularly true for low values of the coefficient of friction against the barrel. The high sensitivity to the coefficient of friction will tend to result in unstable extruder performance. At high values of the barrel coefficient of friction the extruder performance will be less affected by changes in friction and the extruder will be more stable under these conditions. This explains why grooved feed extruders tend to be more stable than smooth bore extruders. 

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. 

Does it have a grooved feed throat on the barrel ... 

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. 

For many years, plastic extruder feed zones had smooth barrels, but feed zone inserts with grooves to restrain pellet rotation were introduced in Europe in the 1960s and have grown in application, particularly in combination with barrier screws, but less so in North America. 

---