塑料杯成型工艺及注塑模设计

本文对水杯的技术要求和工艺结构进行了分析,确定了工艺方案及模具形式。而且对水杯进行了相关数据的分忻与计算,根据分析结果选注塑机和注塑工艺,从而确定聚丙烯水杯设计思路及方案,最后在设计过程中运用Pro／E、Auto CAD软件进行注塑模结构设计与计算并绘制出模具总装图以及部分非标准图形。     

Modeling of mold filling process for powder injection molding

The mold filling process has been modeled for the injection molding of different polymer-based binders and powder-polymer mixtures. It is essentially a two dimensional non-Newtonian fluid flow analysis in a non-isothermal environment. A complete analysis is accomplished by combining a finite element method and control volume technique to describe an increment of flow front movement, whereas a finite difference method is used to solve the energy equation to characterize the temperature distribution. Numerical results are compared to exact solutions for a circular ring cavity using a power law fluid model under an isothermal condition. Comparison of computed results against published data for a simple circular disk shows good agreement between the two analysis methods. After making selected comparison studies, it is demonstrated that the filling process in Powder Injection Modeling with different combination of powder-polymer mixtures is markedly dependent on specific combinations of powder; and polymer based binders. Computed flow front results for a rectangular cavity also compared favorably against the data for a power law fluid model under non-isothermal conditions.     

注塑工艺对PVC-U合金性能的影响

研究了注塑工艺对PVC-U合金性能的影响,结果表明:在注射温度185℃、注射压力80MPa、注射速度60g/s、注射时间5s的工艺条件下,注塑制品具有较好的力学性能。     

Effects of mold surface conditions on flow length in injection molding process

In this study, to clarify the influence of a mold on thin‐wall molding, the effect of different mold surface conditions on the flow length and mobility (i.e., ease with, which melted plastics can be filled into the mold) in an injection molding process was investigated. Three different coatings were used for the mold surface. Several degrees of roughness were also selected for the mold surface. The results were evaluated by comparing flow length with interfacial tensions, which were derived from Young's formula. Although the interfacial tension exhibited different values, the influence on flow length was generally found to be small. On the other hand, in the mold that gives surface roughness, though the change of interfacial tension was small compared with coatings, the flow length increased linearly with the surface roughness when the roughness exceeded a certain level roughness. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Failure mechanisms in stereolithography injection molding tooling

Stereolithography tooling is a form of rapid tooling that has been used to injection mold limited runs of prototype parts. However, the process is not well understood and tooling life for fine mold features is difficult to predict. Injection molding processing conditions and feature geometry affect the number of parts that can be made before a mold fails. To study the effects of feature geometry, general purpose polystyrene parts were injection molded in molds made of DSM Somos 7110 stereolithography resin. The ACES build style was used, and no polishing was performed on the mold. The experimental results were compared with theoretical models developed for the two failure mechanisms for raised features in a stereolithography mold—failures during injection due to the flow pressure of the injected polymer; and failures during ejection, whereby the part pulled out a feature of the mold. Injection failures occurred in taller mold features due to the force of flow and the feature's geometry. Ejection failures occurred in the shorter features when the stress from the ejection force (distributed over the bond area) exceeded the yield strength of the mold material. Models were developed to predict the number of parts that a mold could make before mold features break off and were validated through experimental results.     

Dynamic modeling of the mold filling process in an injection molding machine

This paper presents the development of a nonlinear mathematical model for the study of the mold filling process in an injection molding machine. The model is formulated by the Reynolds transport theorem which is applied to describe the polymer flow dynamics. The mold filling process can be approximated by the transient phenomenon of the non-Newtonian fluids flowing through a closed conduit. The comparison between the experimental results and the theoretical simulation indicate that the nonlinear model is a reasonable representation of the mold filling dynamics when the acrylonitrile-butadiene-styrene (ABS) is injected into a disk shape mold. The actuation system dynamics of an injection molding machine are also investigated. The results indicate that the nonlinear model can also adequately predict the transient behavior of the actuation system.     

The design of conformal cooling channels in injection molding tooling

Solid Freeform Fabrication technologies have demonstrated the potential to produce tooling with cooling channels, which are conformal to the molding cavity. 3D Printed tools with conformal cooling channels have demonstrated simultaneous improvements in production rate and part quality as compared with conventional production tools. Conformal cooling lines of high performance and high complexity can be created, thus presenting a challenge to the tooling designer. A systematic, modular approach to the design of conformal cooling channels is presented. Cooling is local to the surface of the tool, so the tool is divided into geometric regions and a channel system is designed for each region. Each channel system is itself modeled as composed of cooling elements, typically the region spanned by two channels. Six criteria are applied, including: a transient heat transfer condition, which dictates a maximum distance from mold surface to cooling channel; considerations of pressure and temperature drop along the flow channel; and considerations of the strength of the mold. These criteria are treated as constraints, and successful designs are sought that define windows bounded by these constraints. The methodology is demonstrated through application to a complex core and cavity for injection molding.     

Visualization of in‐mold shrinkage in injection molding process

This article presents an experimental investigation on the visualization of (material/mold) separation development during the in‐mold shrinkage of injection molded parts. The purpose is to correlate the separation times with the shrinkage values. Two cavity designs were studied: (i) a simple rectangular plate (nonconstrained plate) and (ii) a rectangular plate with an obstacle pin (constrained plate). Separation development was recorded using a high speed camera on a designed and manufactured visual mold. The results indicate that although there is a meaningful correlation between shrinkage value and separation time in the nonconstrained mold, this correlation is highly disturbed in the presence of a constraint (here, an obstacle pin). POLYM. ENG. SCI., 47:750–756, 2007. © 2007 Society of Plastics Engineers.     

Properties of rapid prototype injection mold tooling materials

Epoxy acrylate‐based sterolithography resins have been used successfully as tools for injection molding. Molds made out of these resins fail at distinct times: during the first injection of plastic; during the first part first ejection; during either injection or ejection, but after a certain number of parts have been produced, which can be compared to a fatigue process. This paper presents corelations between measured properties of stereolithography molds and injection molding processing conditions so as to understand and predict mold failure. The study focuses on two stereolithography resins (SL 7510 and SL 7510) and one epoxy‐based composite material used for the high speed machining of prototype molds (Renboard). Rapid tooling materials are studied in fatigue, tensile, and fracture at injection molding operating temperatures and at room temperature. Finally, a method to address failure of molds is proposed using the theory of fracture.     

Production of injection molding tooling with conformal cooling channels using the three dimensional printing process

A Solid Freeform Fabrication Process called Three Dimensional Printing is applied to the fabrication of injection molding tooling with cooling channels which are conformal to the molding cavity. The tool is created by spreading layers of stainless steel powder and selectviely joining the powder in the layers by ink‐jet printing of a binder material. Unbound powder is removed from without and within the green part thus defined. The green part is sintered and infiltrated with a copper alloy to produce a fully dense tool. The infiltrant is kept out of the cooling channels by elevating the tool above the free surface of the pool of infiltrant in the crucible, thus creating a controlled negative pressure within the infiltrant. An upper limit to the separation of tooling cavity and cooling channel was derived based on transient heat transfer considerations. A tooling set was created to mold a split ring shape and conformal cooling channels were placed in both the cavity and core sides of the tool. The performance of this tool was compared against the performance of a tooling set with straight cooling channels. Thermocouples buried in the core and cavity showed that the conformal tool had no period of transient behavior at the start of molding, while the tool with straight channels took 10–15 cycles to come to an equilibrium temperature some 40°C above the temperature of the coolant. The conformal tool was also found to maintain a more uniform temperature within the tool during an individual molding cycle. The gap in the molded split rings did not change from cycle to cycle with the conformal tool, while it did with the conventional tool. A 2‐D finite difference model accurately captured the observed temperature histories of the mold with conformal cooling channels.     

成型工序设备及工装的改造

对成型工摩几项设备及工装存在的问题、相应的改进方案以及效果分析进行了阐述。认为通过对设备及工装进行适时、适当的改进可以起到满足工艺要求、降低能耗和成本、提高劳动效率、保证产品质量等作用。     

Adaptive model following control of the mold filling process in an injection molding machine

This paper is concerned with the practical application of the adaptive model following control (AMFC) theory on the cavity pressure control of the mold filling process in an injection molding machine. The experimental results indicate that the AMFC technique based on the modified Popov-Landau method is very useful for the cavity pressure control. Two kinds of control algorithms are implemented on a 16 bit microcomputer to control the cavity pressure. The results also show that the AMFC algorithm is superior to the classical PI control in this system when the acrylonitrile-butadiene-stryrene (ABS) is injected into a test specimen mold which is designed according to the ASTM code.     

纤维增强塑料注射充模过程中纤维对模具的冲蚀磨损模拟

针对塑料模具在玻璃纤维冲蚀下造成的表面磨损问题,运用有限元软件ANSYS/LS-DYNA建立了模具材料多颗粒冲蚀有限元模型,进行三维显式冲击动力学计算,研究纤维在不同冲蚀速度和冲蚀角度下对模具的冲蚀规律,分析冲蚀机理。结果表明,玻璃纤维对模具的冲蚀过程以微切削为主;玻璃纤维对模具的冲蚀磨损率随着冲蚀速度的增加而增加,随着冲蚀角度的增加而呈现先增加后减小的趋势。     

The plasticating process in injection molding

A mathematical representation of the plasticating process in a reciprocating-screw injection-molding machine has been formulated as a design tool for simulating the effect of processing parameters on the melting performance, the melt temperature, and the pressure profile. Comparisons with experimental data on low density polyethylene (LDPE), acrylonitrile butadiene styrene (ABS), and polyvinyl chloride (PVC) under a wide variety of processing conditions are described.     

Characterization of mold fouling during elastomer injection molding

Consideration is given to the characterization and origins of mold fouling occurring during the injection molding of elastomers. Results for nitrile rubber and fluoroelastomer compounds are presented with a range of techniques, including light microscopy, scanning electron microscopy, elemental analysis by energy‐dispersive X‐ray spectroscopy, X‐ray photoelectron spectroscopy, and surface‐energy measurements with the sessile drop approach. A specially designed mold tool combined with interchangeable cavity inserts has also enabled the exploration of the effects of different metal surface treatments on the onset and extent of mold fouling. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3186–3194, 2006     

新型注塑成型工艺

介绍了在传统注射成型工艺的基础上逐渐发展起来的几种新型注射成型工艺。气体辅助注射成型、多层共注成型和气体辅助多层共注成型、并对其进行了较详细的描述。     

Effects of inserts on the injection molding process

Injection molds often contain blocks of dissimilar material for improved cooling; they may also contain blocks of movable metal as a means of ejecting large parts from the mold. In this case, the blocks of metal are made of the same material, but the resistance at the interface between them has a marked influence on the cooling in the local area near the interface. In many other cases, inserts may be required because of wear in a particular mold section, or because efficient mold design is needed to produce similar parts. Hence, any mathematical model for analysis of heat transfer in injection molds must be general enough to apply to interfaces with and without gaps (i.e., with and without resistance to the flow of heat at the interface) for similar, as well as dissimilar, materials. A new and accurate model for prediction of heat transfer in heterogeneous (zoned) molds is presented in this paper. Through the solution of real problems with this model, the effects of differing material properties and interfacial thermal resistance are studied and the results are reported. It is observed that inserts have both local and global effects on the injection molding process; the overall ejection time for a part may be shortened, and the surface appearance of a part may be improved by correct placement of inserts.     

多级注射成型工艺条件及控制要点

计算机在注塑机上的广泛应用,使多级注射在塑料制品成型加工上成为可能,满足了加工大型塑料制件、复杂精密塑料制品的需要,使注射成型工艺条件的重复精度得到提高。     

Numerical simulation of mold filling in reaction injection molding

A two dimensional finite element model for the simulation of the advancing front in reaction injection molding (RIM) is presented. The model is based on the solution of the full Navier-Stokes equation for the computation of the velocity and pressure. The arbitrary Lagrange-Euler method is used for the moving front. The method of characteristics is used for the solution of the mass-and energy equations. An automatic remeshing algorithm is used to prevent element distortion and to optimize element size and number. Numerical results are presented for flow into a complex domain in order to illustrate the versatility of the method.     

A study on the mold filling process in resin transfer molding

A numerical simulation of the mold filling process during resin transfer molding (RTM) was performed using the boundary element method (BEM). Experimental verification was also done. Darcy's law for anisotropic porous media was employed along with mass conservation to construct the governing differential equation. The resulting potential problem was solved with the boundary element technique. As the calculation domain changed due to the proceeding resin front, boundary nodes were rearranged for each time step. The node which goes out of the calculation domain as time progresses was relocated at the intersection between the solid boundary and the line drawn between the node at previous and at current time steps. Results showed good agreement with data for a rectangular mold. To evaluate further the validity of the model, the area velocity of the resin-impregnated region during mold filling was calculated. The area velocity thus calculated was compared with the corresponding resin inlet velocity to check the mass conservation. A close agreement was observed, which renders confidence in the resin front proceeding algorithm. Numerical calculations were also performed for complicated geometries to illustrate the effectiveness of the current method.