Geometry of Self-Wiping Extruders

when the diameter, centerline distance, and number of flights are selected, the tip angle and thus the flight width are fixed by Eq. 10.3. The angles at and aj are angles in the plane perpendicular to the screw axis see also Fig. 10.12. 

Geometry of self-wiping twin screw extruders 

the centeriine distance can be expressed simpiy as L = D COSO  

When the angle of intermesh is zero, the centerline distance simply equals the screw diameter. The maximum channel depth at the root of the screw is given by  

Once the tip angle and the number of flights are selected, the centerline distance and the root diameter are fixed in a self-wiping co-rotating extruder. This imposes a considerable design constraint on co-rotating twin screw extruders. 

---

Here fp and f s are correction factors for the channel geometry, and Hq is the maximum channel depth. In case of rectangular screw chaimels the correction factors can be calculated analytically [Eqs. (2.6) and (2.7)] for the complex geometry of self-wiping extruders they can be approximated by Eq. (2.32) or they can be calculated numerically (6). The number of parallel channels in a screw with m thread starts equals 2w — 1. This leads to a throughput for a self-wiping twin-screw extruder of (6,7)... 

---