Modular twin-screw design

Knowing the head pressure prior to running material will aid extrusion personnel in system design and semp. For example, a high HPI value may indicate that the placement of a vent port on a modular twin screw line should be located further back from the die to prevent melt flow. Or, it may simply indicate that the assumed screw speed should be lowered for safety reasons. A low HPI value may point to the need for a tighter screen pack design in order to promote more mixing. 

S. Lim and J. L. White, Flow Mechanisms, Material Distribution and Phase Morphology Development in a Modular Intermeshing Counterrotating Twin Screw Extruder of Leistritz Design, Int. Polym. Process., 9, 33—45 (1994). 

For a majority of applications, the modular design has been accepted for the twin screw extruder. This allows optimum adjustment of wear protection in the respective process zone and material selection for the corresponding process zones to ensure a maximum life span. 

More expensive but easier to control is a twin screw extruder, TSE. Owing to the modular design with many types of elements fulfilling different functions, TSE can be optimized for specific tasks. The ratio of the dispersive to distributive mixing can be adjusted, and the width of the residence time can be controlled. TSE is excellent chemical reactor for polymerization, modification... 

TSE, Modular design of 21, 609, 610, 618-620 see also Extmder, Twin-screw... 

The design variables can be further subdivided into three groups extruder, screw, and die design. A twin-screw extruder is schematically depicted in Fig. 6.2, and it consists of a heated barrel that encloses the screws, which convey the material forward and force it through the die. Extruders are primarily defined by the diameter of their screws and their length to diameter ratio (LID). The barrel can be modular or fixed, and is independently heated and cooled by means of a control system. 

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