Extrusion systems high-output

Co-Rotating Twin Screw Extruder (CTSE). This system is commonly used for compounding and profile extrusion in high output applications. CTSE with its high shear is, however, harder to control than the counter rotating system (see below). 

Ontario, 12th-14th Oct.1999, p.48-51 NEW LOW PLATE OUT RIGID PVC LUBRICANT SYSTEM TO MEET THE PROCESSING CHALLENGES OF TODAY S HIGH-OUTPUT EXTRUSION PROCESS Decker R W Falter J A Henkel Corp. 

The output rate of the extruder is a function of screw speed, screw geometry, and melt viscosity. The pressure developed in the extruder system is largely a function of die resistance and dependent on die geometry and melt viscosity. Extrusion pressures are lower than those encountered in injection molding. They are typically 500 to 5000 psi (3.5 to 35 MPa). In extreme cases, extrusion pressures may rise as high as 10,000 psi (69 MPa). Variants on the single screw include the barrier or melt extraction screw and the vented screw (Chapter 3). 

These patterns are often related to line tension, more specifically uneven line tension. In advanced cast film lines (BOPP or BOPET), there are tension-control systems that allow tension adjustment in specific regions of the film. In these lines, a gear pump is often necessary to minimize output variation. The diehead pressure in such extrusion operations can be very high (up to 600 bar). 

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