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Mold Cavity (mold + cavity)
Selected AbstractsVisual perception and measurements of texture and gloss of injection-molded plasticsPOLYMER ENGINEERING & SCIENCE, Issue 2 2009Sofie Ignell The effect of an imposed texture on the gloss of injection-molded polymeric surfaces was evaluated as well as the way in which these properties are visually perceived. Specimens having small differences in surface topography were produced using two mold cavities with slight differences in texture and three different polymers. The texture and gloss were characterized using laser profilometry, gloss measurements, and by means of psychometric evaluations. The measured surface topography parameters and gloss were determined mainly by the texture of the mold surface and the gloss also by the processing conditions. Variations in surface topography due to differences in the rheological properties of the polymer melts were, in most cases, too small to be reflected in the measurements. The visual assessments of the texture and the gloss of specimens from the same cavity were in fair agreement with the measurements, although the observers could discern differences between some specimens not revealed by the measurements. When the specimens molded in the two cavities differing significantly both in gloss and texture were compared, the agreement between the measured topography parameters and the perceived roughness was poorer. It is suggested that higher gloss of a textured surface enhances the perception of a higher roughness. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers [source] Effects of process parameters on the micro molding processPOLYMER ENGINEERING & SCIENCE, Issue 9 2003J. Zhao The trend towards miniaturization has brought about strong demand for increasingly smaller precision-molded plastic components. In order to control metering accuracy and homogeneity of the very small quantities of melt in the micro molding process, new micro molding machines that use an injection system comprising a screw extruder and a plunger injection unit have been developed. By use of such injection systems, standard plastic granules can be handled by the screw extruder and melt accuracy can be achieved by the electrically driven injection plunger. The objective of this work is to investigate the effects of the process parameters on the micro molding process and part quality. A series of micro gears were molded using a polyoxymethylene resin in a set of statistically designed experiments. Micro component inspection, characterization, and data analysis work was carried out to study the molded gears. It was found that metering size and holding pressure time are the process parameters that have the most significant effects on part quality, and that the process is also significantly affected by the interaction of these two parameters. There is an optimum metering size range in which the hold pressure can act together with the metering size to properly fill micro mold cavities. [source] Centrifugal Gel Casting: A Combined Process for the Consolidation of Homogenous and Reliable CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2010Saeed Maleksaeedi In this work, a combined process, called centrifugal gel casting (CGC), was proposed for the fabrication of homogenous and reliable monolithic and composite ceramics starting from submicrometer-sized powders. This method exploits the advantages of both conventional gel casting (GC) and centrifugal slip casting (CSC), while overcoming the limitations associated with the two methods. Via this process, a relatively low centrifugal force is applied to form a highly concentrated slurry in the mold cavity, which is then followed by in situ polymerization of slurry during gelation. In this work, concentrated alumina slurries with different solid contents from 45 to 65 vol% were consolidated by the three forming methods mentioned above. Various properties of green and fired products were measured and compared. Shorter processing time, lower centrifugal force, higher green strength, and minimal segregation are observed to be the characteristics of CGC in comparison with CSC. In situ elimination of bubbles with no need for degassing and the ability to remove heterogeneities, on top of high reliability and the potential to process higher viscosity slurries, are the main advantages of this method over the conventional GC. [source] Optimization of cure kinetics parameter estimation for structural reaction injection molding/resin transfer moldingPOLYMER COMPOSITES, Issue 6 2001Robert J. Duh A numerical method is proposed for polymer kinetic parameter estimation of either Structural Reaction Injection Molding (SRIM) or Resin Transfer Molding (RTM). The method simulates either radial flow or axial flow of reactive resins through a fiber preform inside a mold cavity. This method considers a non-isothermal environment with different inlet boundary conditions. Based on the molding conditions, this method can find the best values of chemical kinetic parameters by comparing the simulated temperature history and the experimental temperature history. Since the kinetic parameters are estimated with the real molding conditions, the simulations using these parameter values can have better agreement with molding data than those parameters which are obtained from idealized conditions such as Differential Scanning Calorimeter (DSC). The optimization approach was verified by estimating kinetics parameters for RTM data available in the literature. Temperatures predicted by the optimized kinetics parameters are compared with experimental data for two different molding conditions: injection of a thermally activated resin into a radial mold under constant pressure flow, and injection of a mix activated resin into a radial mold under constant volume. In both cases, the optimized kinetics parameters fit the temperature data well. [source] Analysis of the vacuum infusion molding processPOLYMER COMPOSITES, Issue 1 2000A. Hammami The vacuum infusion molding process is becoming increasingly popular for the production of large composite parts. A comprehensive model of the process has not been proposed yet, making its optimization difficult. The flexible nature of the vacuum bag coupled to the varying pressure inside the mold cavity results in a variation of the cavity thickness during the impregnation. A complete simulation model must incorporate this phenomenon. In this paper, a complete analysis of the vacuum infusion molding process is presented. The analysis is not restricted to the theoretical aspects but also reviews the effect of the main processing parameters. The parameters investigated in this paper are thought to be those of most interest for the process, i.e. the compaction of the reinforcement, the permeability, the infusion strategy and the presence of flow enhancement layers. Following the characterization experiments, a 1-D model for the vacuum infusion molding process is presented. This model is derived assuming that an elastic equlibrium holds in the mold cavity during mold filling. Even though good agreement was found between simulation results and experiments, it is concluded that additional work is needed on the numerical model to integrate interesting findings from the experimental part. [source] Overall numerical simulation of extrusion blow molding processPOLYMER ENGINEERING & SCIENCE, Issue 8 2000Shin-Ichiro Tanifuji This paper focuses on the overall numerical simulation of the parison formation and inflation process of extrusion blow molding. The competing effects due to swell and drawdown in the parison formation process were analyzed by a Lagrangian Eulerian (LE) finite element method (FEM) using an automatic remeshing technique. The parison extruded through an annular die was modeled as an axisymmetric unsteady nonisothermal flow with free surfaces and its viscoelastic properties were described by a K-BKZ integral constitutive equation. An unsteady die-swell simulation was performed to predict the time course of the extrudate parison shape under the influence of gravity and the parison controller. In addition, an unsteady large deformation analysis of the parison inflation process was also carried out using a three-dimensional membrane FEM for viscoelastic material. The inflation sequence for the parison molded into a complex-shaped mold cavity was analyzed. The numerical results were verified using experimental data from each of the sub-processes. The greatest advantage of the overall simulation is that the variation in the parison dimension caused by the swell and drawdown effect can be incorporated into the inflation analysis, and consequently, the accuracy of the numerical prediction can be enhanced. The overall simulation technique provides a rational means to assist the mold design and the determination of the optimal process conditions. [source] Effects of defrosting period on mold adhesion force of epoxy molding compoundASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2009Hwe-Zhong Chen Abstract In integrated circuit (IC) packaging, when epoxy-molding compound (EMC) is filled in the mold cavity and cured in the mold, adhesion occurs in the interface between EMC and the mold surface. Too large an adhesion force can cause many problems. For example, too large an adhesion force may damage an IC during ejection and cause the package to fail and thus lower the yield rate. To resolve mold adhesion problems, improving the mold design and applying suitable surface treatments, such as mold surface coating, are the common approaches. Applying suitable surface coating is a more popular and practical approach. Defrosting is a process to increase the frozen EMC temperature to room temperature, and to retain it at room temperature for some period before molding. It is a common practice to put EMC under required atmospheric environment during defrosting. It has been found by molding engineers that increased defrosting period will increase the frequency of mold cleaning. But there is no quantitative description on how much the adhesion force increases during the defrosting process. This paper describes the use of a semiautomatic EMC adhesion force test instrument to measure the normal adhesion force between the mold surface and EMC. By measuring the adhesion force, one can quantify how much adhesion force exists between EMC and the mold surface under different defrosting periods. The results show that it is best to use the EMC with 24,32 h of defrosting, to prevent excessive amount of mold adhesion force and it has been found that the adhesion force of the 24 h defrosting period will be 24% less than that of the 48 h defrosting period. Decreasing moisture absorption will decrease the increase in adhesion force for prolonged defrosting period cases. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd. [source] | ||||||||||