Large-radii screw

The solids conveying data indicate that two competing factors are controlling the rates. The rate reduction caused by a decrease in the cross-sectional area perpendicular to the flight for the large-radii screw is the most obvious factor. As the radii of the flights are increased, the area perpendicular to the flight tip decreases and... 

The vee form of hopper, with inclined front wall oriented square to the screw axis, formed two front gullies down which the material would not flow. Material that built up on these gullies provided a steep, large-radius mass of permanent product at each side of the hopper front. 

Equations 7.57(a) and (b) assume a zero radius of curvature between the flight flank and the screw root. If the radius is taken into account, the screw contact area is reduced by Rc(4 -ti). From this point of view one would like to use a large radius i.e., R. = H. The resulting flight geometry is shown in Fig. 7.13 and also in... 

The possibility that the core of a dislocation could be empty was first recognised by Frank [1], If the strain energy density arising from a dislocation is sufficiently large, it may become energetically favourable to remove the material near the core and place it in an unstrained environment far from any dislocations. This process creates additional surface area around the core of the dislocation. The equilibrium radius of the hollow core of a screw dislocation is given by... 

To convert solid pellet feed into uniform melt, moderate screws with some shallow flights are recommended. Melt flow is kept uniform in the mold with small gates (which maximize shear), large vents, and large sprues for smooth mold filling. Runners should be balanced and radiused for smooth, uniform melt flow. Recommendations, such as bal-... 

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