机筒沟槽和螺杆螺槽耦合作用下的熔融理论研究

对固体输送段和熔融段机筒开设螺旋沟槽的单螺杆挤出机,构建了基于反压缩比分离型螺杆和正压缩比沟槽机筒的耦合双槽熔融模型,并通过液压剖分式单螺杆挤出机实验平台对耦合双槽熔融模型进行了验证。结果表明:对于沟槽机筒单螺杆挤出机,利用熔融段沟槽固体塞和螺杆螺槽固体塞在机筒沟槽和螺杆螺槽界面处发生层间剪切产生的大量内摩擦热来实现物料的高效熔融是可行的;实验结果和理论模型相一致;螺杆转速对熔融长度影响不大,而螺杆结构参数则对其影响较大。     

沟槽机简单螺杆挤出机塑化性能的模拟研究

对传统光滑机筒单螺杆挤出机、固体输送段沟槽机筒单螺杆挤出机和熔融段沟槽机筒单螺杆挤出机的结构特点、输送机理、熔融热源以及熔融模型进行了对比分析,并对其熔融过程中熔融速率、熔融长度和熔融起始点进行了数值模拟,根据模拟结果分析了机筒结构形式对单螺杆挤出机熔融性能的影响。结果表明,机筒内壁开设沟槽的单螺杆挤出机在结构、机理和性能等方面均优于传统光滑机筒单螺杆挤出机,且将机筒沟槽由固体输送段延伸至熔融段对单螺杆挤出机的熔融性能有显著的提高。     

沟槽机筒单螺杆挤出机塑化特性的实验研究

采用剖分式机筒单螺杆挤出机实验平台,对熔融段沟槽机筒单螺杆挤出机塑化过程中熔融起始点、熔融长度、熔体温度/压力等塑化性能及产量进行了实验研究,比较了不同物料在不同工艺条件下对沟槽机筒单螺杆挤出机塑化特性的影响。结果表明,增大螺杆转速或提高机筒温度,塑化过程实际所需熔融长度增加,但对熔融起始点影响不大;熔融段机筒沟槽内熔体温度和熔体压力随螺杆转速增大无明显变化;随螺杆转速增大,沟槽机筒单螺杆挤出机挤出产量呈线性增加,表现出良好的挤出特性。     

沟槽机筒单螺杆挤出机固体输送产量的粒径模型研究

在分析机筒衬套沟槽槽深、螺杆螺槽槽深和加工物料粒径关系的基础上,建立了沟槽机筒单螺杆挤出机3种常见的固体输送段产量粒径模型,该模型可用于研究机筒衬套沟槽槽深、螺杆螺槽槽深和颗粒物料粒径对固体输送机理的影响并定量计算沟槽机筒单螺杆挤出机固体输送段产量。此外,通过不同的机筒和螺杆组合及不同粒径的原料在自制的在线模拟试验机上对该模型进行了验证和试验分析。     

开槽机简单螺杆挤出机的对比研究

针对轴向直槽机筒单螺杆挤出机和螺旋沟槽机筒单螺杆挤出机的结构、固体输送机理和优缺点进行了对比分析,并对其比产量和比能耗进行了对比实验研究.结果表明,通过正确的沟槽结构设计,可实现螺旋沟槽机筒单螺杆挤出机固体输送段的正位移输送,螺旋沟槽机筒单螺杆挤出机在比产量、比能耗等挤出性能指标方面均优于轴向直槽机筒单螺杆挤出机.     

瞬态熔融理论在单螺杆挤出机中研究进展

总结了瞬态熔融理论的发展历程,并对比了其与螺杆挤出行业中的强制熔体移走的熔融理论。总结了瞬态熔融理论应用于单螺杆挤出机的相关熔融理论的研究,指出将瞬态熔融理论与沟槽机筒和分离型螺杆结合,理论上可提高单螺杆挤出机熔融能力的提升,从而匹配沟槽机筒单螺杆挤出机的高固体输送效率,提升单螺杆挤出机的产量和制品质量。     

螺旋沟槽单螺杆挤出机双螺棱推动理论模型的研究

通过在单螺杆挤出机固体输送段机筒内壁开设螺旋沟槽,建立了将机筒与螺杆视为一个对物料协同作用的整体的新型物理模型——弧板模型;同时将嵌入机筒沟槽与螺杆螺槽中的物料视为固体塞,提出了新型"双螺棱推动理论",弥补了单螺杆挤出机不能实现正位移输送的传统理论缺陷;最后,通过理论分析确定了螺旋沟槽挤出机由摩擦拖曳输送向正位移输送转换的边界条件方程及正位移输送下沟槽结构参数的设计准则。     

耦合双槽单螺杆挤出机停留时间研究

提供了一种全新的分析挤出机停留时间的方法。在相同螺杆转速下,耦合双槽单螺杆挤出机物料的停留时间低于传统光滑机筒单螺杆挤出机和螺旋沟槽IKV单螺杆挤出机;耦合双槽单螺杆挤出机可以有效提高挤出机的熔融效率,实现高固体输送产量下的熔融效率与固体输送效率的匹配。     

德国开发多种塑机新品

德国Paderborm大学开发出一种新的挤出机结构设计理念，已被德国Extrudex塑料机械有限公司用于工业化生产单螺杆挤出机Helibar，应用在挤出管材和吹塑(中空成型)中。Helibar的长径比为36/1，特点为整个机筒长度都有螺纹沟槽，加料段的沟槽深，其他部分沟槽浅，螺杆为专用屏障型结构，转速高于一般单螺杆挤出机，产量特别大。     

单螺杆FDM线材挤出机机筒结构分析与优化设计

对机筒的加热器位置、机筒长度和机筒内径等影响单螺杆FDM线材挤出机挤出成型的机筒结构因素进行了分析,以压力梯度、出口平均温度和流场平均温度为试验指标,基于ANSYS Workbench软件进行正交试验和极差分析,得到最优因素组合。并在试压工况、正常工况、极限工况和极限冷态工况等4种工况下,对采用最优因素组合设计的机筒进行了热力耦合试验验证。试验结果表明:当机筒的加热器位置43 mm、机筒长度270 mm、机筒内径15 mm时,单螺杆FDM线材挤出机出丝顺利,效率较高且安全可靠。     

Melting performance of single screw extruders with a grooved melting zone

A novel melting model for single screw extruders with a grooved melting zone was established. The whole solid plug, which came from the grooved feed zone, was ruptured and melted mainly by continuously changing the volume of the barrel grooves and the screw channel in the grooved melting zone. A new single screw extruder platform with hydraulic clamshell barrels was constructed to investigate the melting of solid polymer with different combinations of barrels and screws. The melting model was verified by experiments. The results showed that the melting started earlier and finished in a shorter length for single screw extruders with a grooved melting zone than that for conventional single screw extruders and the melting efficiency was improved by introducing a grooved melting zone to a single screw extruder. The theoretical values are consistent with experimental results. The novel single screw extruder with grooved melting zone can dramatically increase the plasticizing efficiency and the throughput.     

开槽机筒单螺杆挤出机的研究进展

分析了轴向直槽机筒单螺杆挤出机和螺旋开槽机筒单螺杆挤出机在基本结构、物料输送机理及工业应用领域等方面的不同。随着开槽机筒单螺杆挤出机产量的提高,常规的熔融方式无法实现高产量下物料的高效彻底熔融,因而开槽机筒单螺杆挤出机存在产量与熔融能力无法匹配的问题,通过分析现有解决途径,指明了其未来的发展趋势。     

Melting model for modular self wiping co-rotating twin screw extruders

A model for the melting process in a self wiping co-rotating twin screw extruder is described. Self-wiping co-rotating twin screw extruders are modular and starve fed. This leads to melting mechanisms that are different from single screw extruders. The melting process in the modular screw configurations generally occurs in specialized sections such as kneading disk blocks. The model, based on our previous experimental observations, considers the formation of two stratified layers of melt in contact with the hot barrel and solid pellets in contact with the relatively colder screw. In the kneading disk blocks, a part of the solid bed is blocked because of the relative stagger between successive disks. The model predicts both the location of melting and melting lengths in a screw configuration. Calculations for individual screw elements and kneading disc elements are presented first. Melting in a modular configuration of these elements is then considered. The effect of operating variables such as mass flow rate and screw speed on melting is then studied. The model is put in a dimensionless form and the effect of various dimensionless groups is discussed. We make a comparison to the experiment and agreement is good.     

Melting of thermoplastics in single screw extruders

Some experiments on the melting of thermoplastic polymeric materials in single screw extruders are described. Although these were of the now familiar screw extraction type, special care was taken to distinguish between material melted by screw rotation and that melted during the subsequent cooling operation. A barrel which could be split longitudinally was also used, thus avoiding some of the disadvantages of axial extraction. A theoretical model is proposed which, unlike previous models, allows the solid bed of material in the screw channel to accelerate naturally, and also allows for the presence of a film of molten material between the bed and the screw. This model gives satisfactory predictions of melting performance. Comparison with experimental results shows that break-up of the solid bed occurs when the model predicts rapid acceleration of the bed. Bed break-up and the resulting surging may be reduced or prevented by the use of screw cooling which has the effect of inhibiting the formation of a melt film at the screw surface.     

单螺杆挤出机熔融机理研究的发展

介绍了国内外单螺杆挤出机熔融机理研究的发展，分析了熔融理论发展历程及所面临的问题，以及现有熔融理论的适用范围，指出在熔融理论研究应用过程中应根据具体问题，合理选择熔融理论模型，并提出动态熔融机理研究的两个研究重点及理论研究思路。     

数值模拟研究螺筒结构对单螺杆挤出机性能的影响

通过数值模拟研究了机筒内壁开螺槽的螺筒结构对单螺杆挤出机性能的影响。采用POLYFLOW软件模拟了硬质聚氯乙烯(PVC-R)熔体在单螺杆螺筒挤出机以及传统单螺杆挤出机中的三维等温流场及混合过程,并对二者的混合挤出性能进行了比较。结果表明:机筒内壁为螺旋沟槽结构的单螺杆螺筒挤出机,其混合性能相对于传统单螺杆挤出机有所提高。     

Melting process and mechanism for vibration induced single‐screw extruder

The effect of a vibration force field on the melting process of an extruder is studied. It is shown that the mechanism for melting differs from conventional theory. Experimental studies of melting of low‐density polyethylene (LDPE) pellets in a vibration‐induced single‐screw (VISS) extruder show that melting is initiated on the inside of the barrel and the surface of screw. Models were developed that explain the melting mechanism in those regions. The melting at the surface of the screw is mainly initiated by frictional work on the pellets by the vibration and rotation of the screw. The melting action at the barrel is induced by a barrel temperature higher than the melting point and propagated by viscous dissipation heating of the melt film produced. The theory is supplemented by a calculation sample, which shows good agreement with experimental data obtained on a transparent barrel VISS (T‐VISS) extruder and a half‐open barrel VISS (H‐VISS) extruder with LDPE. The results of the experiment and calculation sample indicate that the introduction of vibration‐induced field can improve the melting capacity of extruder to a great extent. The present model enables the prediction of processing parameters for VISS extruders, from which the optimum operating conditions can be obtained. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2504–2514, 2007     

The adjustable grooved feed extruder

Grooved feed extruders have been around since about the 1960s. These extruders offer considerable advantages over conventional extruders, such as higher throughput, better stability, and the ability to process very high molecular weight polymers. There are some important disadvantages as well, for instance, higher motor load, wear is more likely, high pressures in the grooved region, and the screw design has to be adapted. The disadvantages of the grooved feed extruder disappear when the grooved feed extruder is made with a mechanism that allows adjustment of the groove depth. Grooved feed extruders have now been developed that incorporate an adjustment mechanism that allows the depth of the grooves to be changed, during actual operation, from zero to full depth. Chris Rauwendaal and Janusz Sikora explain.     

Analytical melting model for extrusion: Melting rate of fully compacted solid polymers

The melting mechanism inside screw extruders is presently analyzed using numerical, iterative methods that are too complex to be used widely by practicing engineers. Our theoretical and experimental investigations of the melting mechanism have produced simple, analytical equations for predicting the melting rate of fully compacted solid polymers without iterative calculations. The accuracy of these equations was found to be satisfactory. Consideration of the temperature and shear dependencies of the melt viscosity was found to be essential for the accurate prediction of the melting rate.