. For a medium or large-sized gear drive, in order to achieve the optimum weight reduction effect, an approach of weight reduction design is proposed that multi-objective optimization of gear parameters is carried out firstly, and then structural optimization is adopted to design the gear former. The rational design parameters of a gear drive are determined by the multi-objective optimization with minimizing the sum of gear volumes and the equivalent moment of inertia of input shaft (EMI) synchronously. Conceptual design of the former is given by structural topology optimization of the gear, and the reasonability of topology optimization can be demonstrated by static and dynamic analysis. The results indicate that for a double-reduction gearbox of 500KW co-rotating twin screw pulping extruder, the EMI of the gear drive reduces by 20.88% through the multi-objective optimization of gear parameters, and the moment of inertia of a bull gear reduces by 38.86% through structural topology optimization.

In order to enhance design reliability of a co-rotating twin screw pulping extruder (TSPE), optimum design on screw parameters of the TSPE was studied based on the extrusion model. The maximum shear flux or the minimum power consumption, or the two synchronous optimizations were taken as objective functions, and constraint conditions, such as thread lead, depth of thread, screw rotational speed, number of reverse thread lead, actual top width of the flight, torsional strength and stiffness of the screw mandrel, and so on were confirmed base on actual requirements of the TSPE manufacture and application. The optimizing results show that two-objective optimum design results split the difference of the two single-objective optimum design, and it is the most economical in reducing manufacture cost of the equipment and pulping expenses.

In order to calculate important design parameters, screw axial force and power consumption of twin screw pulping extruder (TSPE), considering actions of the solid material plug in reverse thread of the TSPE and according to static balance principle, an extrusion model including plug flowing and shearing in reverse thread is proposed in the paper. Based on the model, screw axial force, screw torque, power consumption and flow rate can be derived. When changing thread lead numbers or slot width on the flight of the reverse thread, theoretical calculating results and testing results are better consistent.

In order to design trapezoidal thread parameters of co-rotating twin screw extruder that is used in non-fused materials processing, based on geometry of fully wiped co-rotating twin screw extruder by M. L. Booy, the paper adopts tangential approximation method to determine the parameters of trapezoidal thread choosing tangent of especial point of normal section curve. And reasonable spans of oblique angle, actual top width of flight, channel depth and thread lead are determined by the optimum design with objective function of maximal theoretical flux. Experiments show that a co-rotating twin screw pulping extruder of trapezoidal thread designed by the method is easier to machine and measure, and pulp processed by the twin screw pulping extruder can meet the quality requirements. Thus, twin screw designed by the method reserves the main strongpoint of the fully wiped co-rotating twin screw extruder.

In order to reduce the energy consumption and gear’s weight of drive system, based on electromechanical driving dynamics, the paper discussed the influence on rotary inertia of motor shaft caused by drive system of multi-shaft varying speed and its actuator, analyzed the influence on energy consumption and cycle of the motor’s startup or brake by sum rotary inertia (SRI), and explained the problems related to rotational speed of the motor and drive system design, also brought forward methods on weight reduction design (WRD) of drive system. Case studies show that in multi-shaft reduction drive, the ratio of the drive system rotary inertia on the SRI of the motor shaft is from 5.377% to 18.567%. Therefore, weight reduction of the drive system has obvious effect on lessening the energy consumption and cycle of the motor’s startup or brake. And the work of the paper offers theoretical gist for WRD of drive system.