Injection Moulding Simulation Research Articles

Enhancing Injection Molding Simulation Accuracy: A Comparative Evaluation of Rheological Model Performance

Enhancing Injection Molding Simulation Accuracy: A Comparative Evaluation of Rheological Model Performance

Analysis of the Similarity between Injection Molding Simulation and Experiment.

In the plastics industry, CFD simulation has been used for many years to support mold design. However, using simulation as a substitute for experimentation remains a major challenge to this day. This is due to the unknown congruence between simulation and experiment. The present work focuses on a comparison between simulation (generated with the software Moldflow Insight Ultimate from Autodesk Inc., San Francisco, CA, USA) and experiment by using molds of different complexity, where, in contrast to a large number of previous investigations, both the characteristics of the parts and the time series of the process parameters were compared with each other. For this purpose, the high-resolution time series of the process parameters injection pressure, flow rate, and cavity pressure as well as the mass and the dimensions of the manufactured parts were acquired during the experiments and the results were compared with the computations obtained from the simulation. In addition, potential causes like the material data, mesh and solver parameter, and the machine-specific behavior were analyzed to assess which of these causes may be decisive for a deviation between simulation and experiment.

Monitoring and modelling the deformation of an aluminium prototype mould insert under different injection moulding and clamping conditions

The conventional material of prototype injection moulds is aluminium. Well-established techniques are available on the applicability of such moulds, yet their operational state is not analysed comprehensively. State monitoring has huge benefits because the mould can be protected from excessive loads and deformations and product quality can be monitored in real time. In this paper, we measured the operational strains, cavity pressure and temperature distribution of prototype injection moulds with the traditional state monitoring method, and analysed the combined effect of holding pressure and clamping force on the operational deformations and cavity pressures. Increasing the clamping force and the holding pressure results in higher operational strains and cavity pressures. The precision of core shift analysis was tested if it can predict operational deformations of aluminium injection moulds. Core shift analysis could accurately predict the maximal deformation but it is inaccurate regarding the time when it occurs. A novel modelling method was also introduced where pressure and temperature results of the injection moulding simulation can be imported into finite element (FE) mechanical simulations. This way, mould deformations can be modelled in mechanical FE simulation environment. The measured operational deformations were compared both with core shift analysis results and with the coupled IM-FE simulation results. Core shift simulation can predict maximal deformations with adequate precision but it does not consider thermal expansion effects properly. In order to improve the accuracy of the simulations, a coupled IM-FE method is necessary, where excellent agreement can be found between the measurements and the calculations. The new, combined modelling technique can improve the accuracy of mould deformation modelling because additional mould material models become available in a professional finite element software. It can be especially useful in the modelling of polymeric mould inserts where stiffness is heavily temperature-dependent and the material creeps.

Optimization of Plastic Speed Meter Housing for Automobiles: Injection Molding Simulation, Taguchi Method and Machine Learning

The plastic speed meter housing for automobiles requires accurate parts and assembly to inform the driver of their exact speed. For accurate assembly, the molded speed meter should have a minimize amount of deformation. In this study, to obtain injection molding conditions that minimize the deformation of the speed meter, the main molding conditions that cause the deformation of the speed meter were identified using the Taguchi method. By combining the confirmed molding conditions, 150 data sets were created, and machine learning was conducted using the data set. The model with the best accuracy learned through machine learning was the Linear Regression model. The results of this Linear Regression model were then validated with test data. The optimal injection molding conditions were derived by inputting 5000 molding conditions data into the learned Linear Regression model. Injection molding analysis was performed using the derived injection molding conditions, and the amount of deformation was reduced by about 6.4% compared to the case where current molding conditions were applied. The optimal molding conditions obtained by machine learning were applied to actcual molding. The amount of deformation of the mold amount of the molded speed meter housing was smaller than the amount of deformation predicted in the machine learning model.

On the Phase Space of Fourth-Order Fiber-Orientation Tensors

Fiber-orientation tensors describe the relevant features of the fiber-orientation distribution compactly and are thus ubiquitous in injection-molding simulations and subsequent mechanical analyses. In engineering applications to date, the second-order fiber-orientation tensor is the basic quantity of interest, and the fourth-order fiber-orientation tensor is obtained via a closure approximation. Unfortunately, such a description limits the predictive capabilities of the modeling process significantly, because the wealth of possible fourth-order fiber-orientation tensors is not exploited by such closures, and the restriction to second-order fiber-orientation tensors implies artifacts. Closures based on the second-order fiber-orientation tensor face a fundamental problem – which fourth-order fiber-orientation tensors can be realized? In the literature, only necessary conditions for a fiber-orientation tensor to be connected to a fiber-orientation distribution are found. In this article, we show that the typically considered necessary conditions, positive semidefiniteness and a trace condition, are also sufficient for being a fourth-order fiber-orientation tensor in the physically relevant case of two and three spatial dimensions. Moreover, we show that these conditions are not sufficient in higher dimensions. The argument is based on convex duality and a celebrated theorem of D. Hilbert (1888) on the decomposability of positive and homogeneous polynomials of degree four. The result has numerous implications for modeling the flow and the resulting microstructures of fiber-reinforced composites, in particular for the effective elastic constants of such materials. Based on our findings, we show how to connect optimization problems on fourth-order fiber-orientation tensors to semi-definite programming. The proposed formulation permits to encode symmetries of the fiber-orientation tensor naturally. As an application, we look at the differences between orthotropic and general, i.e., triclinic, fiber-orientation tensors of fourth order in two and three spatial dimensions, revealing the severe limitations inherent to orthotropic closure approximations.

Peroxide-Based Crosslinking of Solid Silicone Rubber, Part I: Insights into the Influence of Dicumylperoxide Concentration on the Curing Kinetics and Thermodynamics Determined by a Rheological Approach.

Predicting the curing behaviour of industrially employed elastomeric compounds under typical processing conditions in a reliable and scientifically driven way is important for rubber processing simulation routines, such as injection moulding. Herein, a rubber process analyser was employed to study the crosslinking kinetics of solid silicone rubber based on the concentration of dicumylperoxide. A model was proposed to describe the optimal cure time variation with peroxide concentration and temperature, based on the analysis of processing parameters applying kinetic and thermodynamic judgments. Additionally, the conversion rate was described with the aid of a phenomenological model, and the effect of dicumylperoxide concentration on the final crosslink state was investigated using kinetic and thermodynamic explanations. Optimal curing time was affected both by temperature and dicumylperoxide concentration. However, the effects were less pronounced for high temperatures (>170 C) and high concentrations (>0.70 phr). A limit on the crosslink state was detected, meaning that the dicumylperoxide capacity to crosslink the silicone network is restricted by the curing mechanism. Curing restrictions were presumed to be primarily thermodynamic, based on the proton abstraction mechanism that drives the crosslinking reaction. In addition to providing more realistic crosslinking models for rubber injection moulding simulation routines, the results of this study may also explain the chemical behaviour of organic peroxides widely used for silicone crosslinking.

Heat Transfer Analysis of 3D Printed Wax Injection Mold Used in Investment Casting.

Investment casting is one of the precise casting methods where disposable wax patterns made in wax injection molds are used to make a casting mold. The production capacity of precision foundry is determined by the time taken for producing wax patterns, which depends on the time taken for wax solidification. Wax injection molds are usually made of aluminum or copper alloys with the use of expensive and time-consuming computer numerical control (CNC) processing, which makes low-volume production unprofitable. To reduce these costs, the authors present a heat transfer analysis of a 3D printed wax injection mold. Due to the low thermal conductivity of the photopolymer resin, the influence of different cooling channels’ shapes was investigated to improve the time of the manufacturing process. Transient thermal analysis was performed using COMSOL software based on the finite element method (FEM) and included a simulation of wax injection mold cooling with cold air (−23 °C), water, and without cooling. The analysis showed that use of cooling channels in the case of photopolymer material significantly reduces the solidification time of the sample (about 10 s shorter), and that under certain conditions, it is possible to obtain better cooling than obtained with the aluminum reference wax injection mold (after approximately 25–30 s). This approach allows to reduce the production costs of low-volume castings.

Experimental Investigation and Applicability of Multi-Stage Simulations in the Case of a Thick-Walled Injection-Moulded Composite

The structure and mechanical properties of an injection-moulded short glass fibre (GF)-reinforced polymer composite were analysed through simulation methods. Fibre orientation, which evolves during the production of a thick-walled automotive part, was determined with an injection moulding simulation. Next, using the material model for the injected product, the force that resulted from the given deformation was determined with finite element software. To validate the simulation results, the examined products were manufactured with 30% reinforced GF, and then measurements were carried out. The validation of the fibre orientation tensor was achieved with optical microscope images, while the validation of the finite element, which analysed the flexural tests, was carried out through a comparison of flexural rigidity. The aim of the project was to verify the reliability of multi-stage finite element software. According to the results, in the case of a thick-walled GF-reinforced product, it was demonstrated that the integration of a different finite element software could be used reliably.

Injection Molding Simulation of Polyoxymethylene Using Crystallization Kinetics Data and Comparison with the Experimental Process

It is well known that the processing conditions in polymer processing have a high impact on the resulting material morphology and consequently the component’s mechanical behavior. However, especially for semicrystalline polymers, the tools available for predicting the final morphology of injection molding parts still have significant limitations. In order to investigate the potential of injection molding simulation for the prediction of the morphology, POM homopolymer specimens were injection molded. The crystallization kinetics data were measured, and simulations in 3D and 2.5D with and without crystallization analysis were conducted in Autodesk Moldflow. The simulations are found to be good accordance with the experiments. Predicted spherulite size and crystalline orientation factor reveal a good qualitative correlation with optical micrographs. Also, the evolution of these parameters along the flow path is plausible. The simulation is found to be a powerful tool for morphology prediction in polymeric parts. Its applicability, however, is still limited to 2.5D models in Autodesk Moldflow, which, of course, is insufficient for complex, thick-walled 3-dimensional parts.

Simulation Opportunities by a Three-dimensional Calculation of Injection Moulding based on the Finite Element Method

Abstract The simulation of injection moulding is essential to meet quality requirements and to increase the efficiency of the design process. In this paper a 3D-finite element model for the simulation of injection moulding is presented. The model's capability comprises the calculation of velocity, pressure and temperature fields as well as the prediction of the flow front position. The numerical approach is mainly based on the Galerkin formulation. Special emphasis is placed on the handling of polymer compressibility in order to enable a realistic simulation of the packing phase. The numerical efficiency has been largely enhanced through the employment of an automatic time step control. In order to demonstrate the code's capabilities and outline advantages and disadvantages over other simulation systems, the calculation results are compared to experimental data and to results obtained from other numerical models.

Effect of fiber content on the layer structure formation of fibers inside injection-molded products using short glass fiber-reinforced materials

Abstract This study aims to clarify the relationship between the layer structure transition of fibers caused by the change in the flow field and the thermal properties and fiber interaction when the glass fiber content is changed. Polyamide 6 samples with different short glass fiber contents were prepared, and changes in layer structure during the flow process of injection molding were compared using X-ray computed tomography. An injection-molding simulation was performed to compare the changes in the layer structure of fibers during the flow process, and the temperature distribution and shear rate distribution were obtained by numerical analysis. Furthermore, the effect of fiber interaction on the layer structure transition of fibers was considered using a relaxation function composed of the fiber content, fiber shape factor, and strain rate.

Modeling of anisotropic dual scale flow in RTM using the finite elements method

In Liquid Composite Molding (LCM) processes, a fabric reinforcement is placed in a closed cavity and resin is injected into the mold. Almost all reinforcements are dual scale containing fiber tows, which fill at a different rate than the region in between the fiber tows. Simulation of LCM processes can help identify regions that fail to fill. However, the presence of dual scale flow is usually neglected. Here this phenomenon is modeled using Liquid Injection Molding Simulation (LIMS) software in which a complex network of one-dimensional elements is created. This allowed us to simulate transverse and longitudinal flow through the fiber tows taking into consideration the orientation and architecture of the reinforcement and, additionally, adding capillary effects to the model. A sensitivity study has been performed to investigate the effects of properties in non-dimensional form, allowing for comparison with experiments that were conducted to validate the model by visualization of the flow front position and dual scale area dimensions.

Kompozit alkatrész numerikus elemzése mikromechanikai jellemzők figyelembevételével

Az elemzés célja egyrészt egy kompozit anyagból készült alkatrész numerikus elemzése anyagának mikromechanikai jellemzői figyelembevételével, másrészt ehhez kapcsolódóan annak vizsgálata, hogy az eredetileg fémből készült alkatrész kiváltható-e kompozit polimer anyaggal az alkatrész súlyának csökkentése mellett a funkcionális és szilárdsági jellemzők megtartásával. A kompozit alkatrész gyártástechnológiájából eredő anizotrópiájának meghatározásához elvégeztük az alkatrész fröccsöntés technológiai szimulációját, majd a szimulációs eredmények felhasználásával végeselem analízis segítségével meghatároztuk az alkatrész statikus mechanikai terhelés esetén fellépő igénybevételeit.

Impact of rheological model on numerical simulation of low-pressure powder injection moulding

ABSTRACT The aim of this study is to quantify the impact of different rheological models on the accuracy of LPIM numerical simulation. Two different feedstocks were formulated, and rheological profiles were characterised using a rotational rheometer from which the parameters of different rheological models were extracted and then implemented in an Autodesk Moldflow package. Mould filling patterns into a rectangular shape mould cavity were simulated, and then validated using real-scale injections. Depending on the feedstock rheological behaviour, models are not always well adapted to predict the mixture viscosity over the entire shear rate range. Because injections were performed at constant volumetric flow, all the rheological models were successfully used to predict the injected length. However, the simulated pressure through the mould cavity was only accurately simulated using the second-order or matrix models since these viscosity models were able to adequately capture the feedstock behaviour in the shear rate range representing the injections.

Experimental Validation of Injection Molding Simulations of 3D Microparts and Microstructured Components Using Virtual Design of Experiments and Multi-Scale Modeling.

The increasing demand for micro-injection molding process technology and the corresponding micro-molded products have materialized in the need for models and simulation capabilities for the establishment of a digital twin of the manufacturing process. The opportunities enabled by the correct process simulation include the possibility of forecasting the part quality and finding optimal process conditions for a given product. The present work displays further use of micro-injection molding process simulation for the prediction of feature dimensions and its optimization and microfeature replication behavior due to geometrical boundary effects. The current work focused on the micro-injection molding of three-dimensional microparts and of single components featuring microstructures. First, two virtual a studies were performed to predict the outer diameter of a micro-ring within an accuracy of 10 µm and the flash formation on a micro-component with mass a 0.1 mg. In the second part of the study, the influence of microstructure orientation on the filling time of a microcavity design section was investigated for a component featuring micro grooves with a 15 µm nominal height. Multiscale meshing was employed to model the replication of microfeatures in a range of 17–346 µm in a Fresnel lens product, allowing the prediction of the replication behavior of a microfeature at 91% accuracy. The simulations were performed using 3D modeling and generalized Navier–Stokes equations using a single multi-scale simulation approach. The current work shows the current potential and limitations in the use of micro-injection molding process simulations for the optimization of micro 3D-part and microstructured components.

Design optimization of office chair star base leg using product LCM and anisotropic material properties from injection moulding simulation

The aim of this research is to design the office chair leg component through Product LCM using anisotropic material. For every product, Product Life Cycle Management (PLCM) plays a vital role to satisfy the customers requirement; especially on weight factor, the cost, failure rate, Time to market, manufacturing feasibility and aesthetics. The anisotropic material properties are mapped from the injection molding machine package to the software on elemental mesh analysis. In a recent time number of researchers used the injection molding simulation software interface with Finite element analysis software to predict the anisotropic material property induced during the molding process. The analysis of the office chair leg is done with respect to the BIFMA ×5.1 office chair standard. Since the leg must withstand both the bending and torsion load induced due to various caster position, the usage of anisotropic material properties plays a significant role in evaluating its stiffness. ANSYS is used for the structural evaluation, Altair OptiStruct is used for Topology optimization and Moldex3D is used for simulating the injection molding process. The leg is optimized from its concept design and validated in FEA using the process induced anisotropic material properties instead of using the isotropic properties available in the material datasheet. The optimum leg design is achieved, which is passing the stress criteria with the factor of safety.

Injection Moulding Simulation: The Development of Integral Hinges Test Samples Mould Design via Cadmould 3D-F

Injection moulding process ability’s in producing intricate parts such as component with integral hinges, had been established for decades. However, to produce a good product, a niche verification process called simulation need to be performed first. Hence, this research was conducted for the development an integral hinges test samples mould design via injection moulding simulation. The simulation output was used to analyse the injection moulding parameter setting and defects towards the prepared mould design. The runner size and shape was fixed, same as well for the gate location and number of cavities. The test sample that needed to be developed was a sample with an integral hinge at the middle of the injected mould article. Polypropylene PPC 8780 (Total Petrochemical) was selected as the reference material. The research methodology started from using SolidWorks as the solid modelling-computer aided design software to prepare the design. This design was then converted into the stereolithography (STL) format. Cadmould 3D-F injection moulding simulation software was chosen as the computed added engineering analysis tools. Parameters such as temperature and time was monitored. The defects such as sink marks, volumetric shrinkage, warpage, weld lines, and air traps were observed. The results show that the mould design had produced 232°C temperature and 0.179 s time when the molten polymer was completely filled. It also produced several defects such as 0.882 % of volume shrinkage and 0.025 mm of warpage. Some sink marks occurred at the above part of the hinge, with 1 weld line and 9 air traps were also detected after the simulation completes. The conclusion of this finding is, the simulation could assist the mould designer to prepare necessary countermeasures in the actual process, and to prepare a better mould with minimum alteration/repair and accelerating setup/preparation time. Hence, the time and cost of a mould could be reduced, especially for new mould design for integral hinge products.

An approximation to the PTT viscoelastic model for gas assisted injection moulding simulation

An approximation to the Phan-Thien Tanner (PTT) constitutive model is developed with the aim of giving low-cost simulation of Gas Assisted Injection Moulding (GAIM) while incorporating important viscoelastic characteristics. It is shown that the developed model gives a response typical of full viscoelastic models in transient and steady-state uniaxial and constant shear rate deformations. The model is incorporated into a 3D finite element GAIM simulation which uses the ‘pseudo-concentration’ method to predict residual polymer, and applied to published experimental results for a Boger fluid and a shear-thinning polystyrene melt.It is shown that the simulation gives a very good match to published results for the Boger fluid which show increasing Residual Wall Thickness (RWT) with increasing Deborah number. Against the shear-thinning polymer, the quality of match depends upon which of two ‘plausible’ relaxation times is chosen; qualitatively different results arise from two different means of estimating a single relaxation time. A ‘multi-mode’ approach is developed to avoid this uncertainty. It is shown that the multi-mode approach gives decreasing RWT with increasing Deborah number in agreement with the published experimental results, and avoids the issues that arise from estimating a single relaxation time for a molten polymer.

Design and Simulation of Injection Mold for a Laryngoscope

To overcome difficulty in airway management for elderly because in elderly due to loss of teeth, mouth will be collapsed and other old age factors. Troublesome intubation is a bad dream for an Anesthesiologist, especially so in an unforeseen difficult airway which will be harmful to the patient as well as Anesthesiologist particularly in rustic arrangement. In the present work we like to design and fabricate an indigenous camera based laryngoscope which is of ease, effectively accessible and reasonable technique for intubation. This video laryngoscope is integrated with the mobile which can be used as a video display device. It will improve the capability of airway management and will be free from many risk factors along with the existing laryngoscope. In the work mechanical model was design with Catia-V5 and the 3D model was imported into Ansys Software for FEM static structural analysis. Along with this a mold flow analysis is carried to obtain better results while fabricating an actual model

Flow-Fiber Coupled Viscosity in Injection Molding Simulations of Short Fiber Reinforced Thermoplastics

Abstract The main objective of this paper is to numerically investigate the use of fiber-dependent viscosity models in injection molding simulations of short fiber reinforced thermoplastics with latest commercial software. We propose to use the homogenization-based anisotropic rheological model to take into account flow-fiber coupling effects. The 4th-order viscosity tensor is approximated by an optimal scalar model and then implemented in the Moldflow Insight API framework. Numerical simulations are performed for a test-case rectangular plate with three fiber orientation models. The resulting coupled flow kinematics and fiber evolutions are then compared to the standard uncoupled simulations. Interpretations are given based on detailed post-processing of the field results. Certain deformation conditions are expected to be better taken into account, which may also in return lead to an improved fiber orientation prediction. Preliminary confrontation between flow-fiber coupled simulations and existing experimental data is then presented at the end of the paper.