Characteristicsobjectives of optimal design of extruder screw
2018-09-12 10:09:04
There are many new extruder screws planned according to various extrusion theories and functional requirements. The design basis is the ordinary extruder screw. The following are mainly the characteristics and objectives of the optimal design of extruder screw, as follows:
Characteristic:
1, design parameters.
Because of the screw geometry disorder, and many factors affecting the production capacity and power consumption of the extruder, the screw planning parameters are many. For example, for the circular transport section, the geometric parameters affecting Q include Db, theta B, H, W, e and so on. These parameters also affect the temperature rise, moving angle and pressure of materials under certain conditions. In addition, the formula Q = Pi nHDb (Db-H)* [(tg_ * tg_b / tg_ + tg_b) * (W / W + e)] is derived from the motion of solid machinery. Considering the motion process, the material near the screw and the barrel surface presents a melting film phenomenon, the design variables are more and more disorderly.
2, optimize goals.
As mentioned earlier, the functions of the screw sections are different, so the corresponding optimization goals are quite different. As for a section, there are also many problems of optimizing goals. For example, the screw conveying section is required to have high conveying efficiency, low fluctuation of conveying rate and low energy consumption; for the melting section, it is required to have high melting rate, i.e. high energy conversion and transfer efficiency, and for the metering section, besides high productivity and low energy consumption, it is also expected to have stable extrusion and high extrusion mass. In addition, there is still a problem for manufacturers of extruder screw in batches to minimize the screw material consumption as far as possible on the premise that the screw performance and strength and stiffness are satisfactory.
3, many constraints.
Mechanical optimization planning is a process in which mathematical models are established according to the optimal policy and planning requirements of the reservation, constraints are determined according to the operation requirements and conditions, and then optimization methods are selected to find the best planning scheme. The optimization planning of screw requires not only satisfying the strength and strength conditions, but also satisfying the processing conditions of polymer molding, which leads to many constraints on the planning model, thus increasing the difficulty of optimization.
Objective:
There are many objectives for optimum design of extruder screw, the first is to ensure the quality of extruded materials under the premise of achieving the highest production capacity Qmax or minimum power consumption Nmin.
To sum up, many planning parameters, many optimization objectives, and many constraints constitute the primary characteristics of extruder screw optimization design, and lead to the chaos of the optimization process. It is found that the above characteristics are also the common characteristics of the optimal design of polymer processing machinery.
