Nonintermeshing twin-screw extruder

Injection molding Counterrotating, nonintermeshing twin screw extruder Gear pump... 

Counterrotating, Tangential, Nonintermeshing Twin Screw Extruders... 

Finally, the effect of process variables, such as screw speed, differs with twin-screw extruders. Due to positive conveyance, the output of starve-fed twin-screw extruders (Fig. 5.36 b is independent of screw speed and, to some degree, head pressure. Head pressures and melt temperatures of intermeshing twin-screw extruders are also not as sensitive to screw speed as they are in single-screw extruders. In contrast, nonintermeshing twin-screw extruders exhibit output characteristics that are similar to those of single-screw extruders. A comparison of the characteristics of single and intermeshing twin-screw extruders is summarized in Table 5.9. 

RJ Nichols, F Kheradi. Reactive modification of polypropylene with a nonintermeshing twin screw extruder. Proceedings of 3rd Chemical Congress of North America, Toronto, Canada, 1988. 

Figure 2.21 Two different configurations for nonintermeshing twin-screw extruders staggered configuration (top) and matched configuration (bottom).

Figure 2.22 Cross section through a nonintermeshing twin-screw extruder with staggered configuration.

Figure 12.28 Comparison of intermeshing and nonintermeshing twin-screw extruders schematic summarizing the different types of parallel twin-screw extruders and applications.

Counterrotating intermeshing twin-screw extmd-ers have the narrowest residence time distribution followed closely by co rotating intermeshing twin-screw extmders. Counter rotating nonintermeshing twin-screw extruders have the broadest residence time distribution. 

For a welding engineer counterrotating nonintermeshing twin-screw extruder, the barrel section does not appear radically different from the intermeshing barrels shown previously and the drive system components are similar. The only slight difference is the apex area of the barrel where the metal on top and bottom of the bore extend farther toward each other due to the larger screw center line separation distance. 

Fig. 10. Schematic representation of nonintermeshing counterrotating twin-screw extruder.

Since the screws do not intermesh, the nonintermeshing extruder is not subjected to some of the same mechanical tolerance constraints as the other twin-screw extruders. This enables the non-intermeshing machine to be built to an almost unlimited 1/d ratio. A 72 to 1 1/d unit was used for a number of devoli-talization experiments. The enhanced length capability provides a mechanism for the increased internal volume. 

Figure 5.30 Twin-screw extruders (a) counterrotating, fully intermeshing (6) corotating, fully intermeshing and (c) counterrotating, nonintermeshing. ...

Twin screw extruders can be operated with either counter- or corotating screws. Additionally, the screws can be fully intermeshing, partially intermeshing, or nonintermeshing. Figure 7-10 illustrates the various cases. 

Figure 5.14 Diagram showing the difference between (a) intermeshing and nonintermeshing as well as (b) co-rotating and contra-rotating or counter-rotating types of twin screw extruders. (Fteprinted from Ref. 20.)...

The diversity among twin screw extruders is so large that a comprehensive discussion of all the various types would be an enormous undertaking. A description of some of the important characteristics of three basic types of twin screw extruders is given below. Nonintermeshing co-rotating twin screw extruders are not produced commercially and hence are not treated in this section. 

Figure 9.2 Twin-screw extruder, counterrotating, nonintermeshing, for compounding, model HTR2800-511-512-E1. Unit shown has panel open for access to barrel and heater elements. Set of extruder screws shown in front, and seven-zone temperature control panel with loss-in-weight feeder controls and main drive motor controls, stands at right of machine. (Photoprovided by Welding Engineers, Inc.)...

---