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波状注塑螺杆熔体输送机理的研究 总被引:2,自引:0,他引:2
本文在综合分析国内外波状螺杆研究成果的基础下,根据注射机预塑过程的特点,建立了更真实地反映波状螺杆工作机理的三维理论模型。在模型中将背压做为一个重要变量予以考虑,采用分段的二维有限元与差分迭代相结合的方法,对等温幂律流动的速度场,压力场和应力场进行了求解,在计算的基础上又进一步分析了波状螺杆几何参数、预塑工艺条件和物料流变参数对熔体输送总流率、压力降、槽向压力分布及扭矩和能耗的影响。对部分计算结果在注塑机实验台上进行的实验验证表明:采用本文理论模型的计算结果与实验结果相近,说明本文的理论模型和计算方法具有一定的工程实用性。 相似文献
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龚浏澄 《现代塑料加工应用》1991,(1):53-55
挤出与注塑是塑料成型加工中应用最广的两类成型工艺,螺杆是其关键部件,因而对螺杆结构的研究是至关重要的。就单螺杆而言,目前已有各式各样的螺杆,近年来国外在原有的分离型、混炼型螺杆的基础上,又开发出螺杆套螺杆的双螺杆型,压缩—减压型的单螺杆。压缩—减压型螺杆又有能量传递式(ET)螺杆和波状螺杆。波状螺杆与普通单螺杆一样,仍分固体 相似文献
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注射螺杆的可靠性设计 总被引:2,自引:0,他引:2
根据注射螺杆在塑化时的受力情况,应用可靠性设计原理介绍了注射螺杆疲劳强度的可靠度的计算方法,并以实例说明.对注射成型机的设计有一定的应用价值. 相似文献
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目前国际上螺杆压缩机转子最大直径达函816mm,制造这种超大型阴阳螺杆转子需要特殊的大型刀具。根据研究分析和实际生产运用,对超大型阴阳螺杆转子刀具铣刀型线的设计、刀体结构、刀片材料、切削用量等进行了阐述,并提出了解决问题方法,同时重点分析了整体刀具结构的优点。用该套刀具加工的Φ816mm转子的啮合精度,表面粗糙度,均达到设计要求。 相似文献
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The mechanism of fiber length degradation during twin screw extrusion compounding and methods to reduce it through process and machine design are extremely important in discontinuous fiber reinforced composites. Fiber damage along the screw and the extruder die are determined for three screw designs with different mixing sections. The pellet quality, wet-out, and fiber dispersion in the extruded strands are compared. The fiber orientation distributions in the screw are determined to identify regions of higher fiber interaction. The fiber damage during subsequent injection molding has also been determined. The tensile, flexural, and impact properties of the tensile bars are compared. It is found that the residence time, fill-up, and the intesity of mixing during extrusion compounding have a predominant effect on fiber length degradation. The screw designs were seen to have a greater effect on the fiber damage in the 40 wt% glass-filled polymer than the 30 wt% glass-filled polymer. However, the mechanical properties of the 30 wt% glass-filled polymer showed an increasing trend compared to the 40 wt% glass filled polymer. A screw design that provides a balance of the fiber length, wet-out, and fiber dispersion was noted to give consistent mechanical properties. 相似文献
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The paper describes a computer software package applying a steady-state hill-climbing optimization routine to the plastics melt-extruder screw constrained-design problem. The purpose primarily is to introduce the optimal screw-design technique, to show how it is applied to this particular type of problem, to indicate its potential and to encourage its wider use. Screw performance criteria are defined by a theoretical model consisting of the non-Newtonian isothermal polymer flow equations in terms of the screw-geometric variables for particular process conditions. The design method is quite general however and a non-isothermal model may be substituted. Use of the method offers considerable scope and potential for the design engineer to make design processes faster, more positive and logical while reducing the effort required. Interactive use is possible and empirical adjustments can be incorporated with experience. In using the method, the design engineer first specifies the required process conditions of pressure and flow rate at the die and the computer then searches for the set of screw design variables which optimizes the screw power utilization efficiency or any other specified criterion of performance. Such optimal designs are obtained within the set limits of practical constraints on machine dimensions, screw strength and product quality requirements. Some experimental evidence is given relating to the accuracy of the isothermal non-Newtonian polymer flow model and to its use in the design of small diameter extruder screws. The optimal search technique offers considerable potential as a computer-based design tool. 相似文献
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A theoretical model for melting in reciprocating screw injection molding machines is proposed. The model permits the calculation of the solid bed profile as a function of time during the injection cycle. It consists of a dynamic extrusion melting model for the rotation period, a transient heat conduction model with a phase transition for the screw rest period, and a proposed model for the drifting of the beginning of melting during the injection cycle. 相似文献
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Effect of screw design on hopper drawdown of spherical particles in a horizontal screw feeder 总被引:4,自引:0,他引:4
Screw feeders are used to remove material from hoppers and bins at a controlled rate. The evenness of the flow in the bin depends on the drawdown pattern, which in turn depends on the screw and hopper design, shape of the particles and wall friction effects. A key design requirement is to ensure that a progressive increase in the screws volumetric capacity is achieved along the entire length of the hopper's opening so as to produce even drawdown. If this is not achieved then compositional variations in the outgoing stream and other operational problems (such as caking) can be created. Screw designs to date have been generally based on analytical models and at times the predicted flow pattern is not achieved. In this study, the Discrete Element Method (DEM) is used to predict particle transport in a horizontal screw feeder system for a range of conventional screw designs including a variable screw pitch, variable screw flight outside diameters and variable core diameters. The influence of screw choice on the particle mass flow rate, the evenness of particle drawdown from the hopper, power consumption, screw wear and wall friction variations are all investigated. Important features captured by DEM that are not accounted for by the analytic model and which vary strongly between competing screw designs, include the particle circulation in the hopper, shearing of the particle bed in the trough just outside the screw and the spatially varying particle force along the hopper which leads to non-uniform drawdown and to the existence of large stagnant or slow moving zones. The screw design and consequent flow patterns also strongly affect the power draw with variations up to a factor of three and screw wear with large changes in their distribution and magnitude. Finally, the surface frictional properties of the screw are shown to strongly influence the rate of bed compaction within and along the screw leading to strong variation in mass flow rate, uniformity of drawdown and power draw. 相似文献
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讨论了挤出机螺杆熔融段的优化设计问题。以单位产量能耗最小为优化目标 ,建立简化的挤出机熔融段螺杆优化设计的数学模型 ,应用复合形法求解。结果表明 ,计算所得熔融段起、末端的螺槽深度、螺纹顶宽度和螺纹升角均位于或接近文献中所建议的最佳取值范围 相似文献
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对比了通用型螺杆与分离型螺杆对PVC-U复合粉料的塑化效果,分析了其结构形式及工作原理,发现分离型螺杆适用于PVC-U复合粉料的加工。 相似文献