Theory and design basis of twin-screw extruder

Theory and design basis of twin-screw extruder

The TSE is assembled to a high torque splined shaft using segmented screws (Figure 2). The barrel is also modular and uses liquid cooling. The motor turns the screw and adds energy to the process. Feeder meter material and screw rpms in the TSE processing section are independent and set to optimize processing efficiency. The segmented screw and barrel with the controlled pumping and wiping characteristics of the co-rotating screw allow the screw/barrel geometry to be optimized for the process task. The solid transport and dissolution process occurs in the first part of the section. Next is the screw element for mixing and devolatilization. A discharge element then creates and stabilizes pressure in the mold or front-end device.

The free volume of the treated section is related to the OD/ID ratio defined by dividing the outer diameter (OD) by the inner diameter (ID) of each screw. A deeper screw flight increases the free volume and reduces the average shear rate, but reduces the torque due to the smaller diameter of the screw shaft.

Control the melting temperature for guideline twins

Figure 2 Co-rotating twin-screw element with asymmetric splined shaft design.

Asymmetrical splined shaft design provides optimum power transmission efficiency, so smaller shaft diameters can transmit higher torque. This is achieved by decoupling the tangential force vectors that transmit from the motor shaft to the screw. High torque, low average shear force, and high OD/ID ratio have proven beneficial in many processes.

In Leistritz terminology, the HP series has an OD/ID ratio of 1.55/1 and uses a symmetrically splined shaft design, while the MAXX series uses a 1.66/1 OD/ID ratio and an asymmetrically splined shaft. uses As the OD/ID ratio increases, the free volume increases by about 20% and the torque rating increases.