The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.
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A Valid Design Prediction Approach of 3D Metal-Printed Mold Manufacturing
In plastic part production, 3D metal printing is a leading manufacturing method for fast, waste-less, and high-accuracy way for making molds with conformal cooling channels. In this automotive power supply test-seat assembly case, the development process combines injection molding simulation, 3D metal printing technology and real experiments to demonstrate an effective mold development approach. Simulation-driven conformal cooling design minimizes the mold temperature difference and significantly reduces part deformation from the traditional straight-line cooling design. Through 6 sets of distance detection, the product dimensions are optimized and can improve the fitting of the three assemblies.
An Investigation of the Crystallinity in Vibration Assisted Injection Molded Poly-Lactic Acid
Vibration assisted injection molding (VAIM) is a process in which a controlled oscillatory movement is introduced to the injection screw during injection molding. This research was focused on the effect of processing parameters on crystallinity and the crystal structures of poly-lactic acid (PLA) during VAIM. It was observed that vibration assisted injection molded PLA products have higher crystallinity than conventionally molded PLA products under similar conditions. Additionally, the cycle time for fabricating PLA parts can be reduced utilizing VAIM without significant loss of crystallinity. The growth of α´ phase of PLA during VAIM and conventional injection molding process was investigated utilizing an X-Ray diffraction technique. A slight phase change from α´ to α phase can be observed in VAIM samples fabricated under certain conditions. The mean size of crystal structures decreased as VAIM frequency increased to 30Hz.
Analyzing the Machine-specific Process Behavior for Automated Adaption of Setting Parameters
As injection molding represents a highly automated, but to the same extend complex manufacturing process to produce e.g. plastic parts without the necessity of post-processing, many efforts focus on compensating fluctuations and reproducing part quality. Injection molding simulation therefore offers the opportunity to determine a valid operating point even before start of production. However, the machine-specific process behavior and the individual machine setup limit transferability of simulated process parameters. Standardized interfaces like OPC-UA for continuous communication with the injection molding machine offer plenty of data from the running production process. Machine data about e.g. screw movements thereby reflect the real-time machine behavior. By analyzing the injection phase at varying injection flow, dosing volume and nozzle temperature with respect to the resulting part weight and the melt cushion, a machine-specific transmission behavior has been observed to adjust settings on different machines based on OPC-UA data.
Blending Scholarly Knowledge and Practioner Know-How To Successfully Injection Mold A Complex Part
A complex piece of sporting equipment was molded to customer satisfaction, meeting critical dimensions despite complicated tooling and the use of a crystalline resin. Combining modern simulation techniques and industry expertise proved to be a winning strategy in solving this challenge. The use of post-molding, warp controlling fixtures was completely eliminated from the legacy production process, leading to improved part performance and plant efficiency.
Direct Compounding of Long Glass Fiber-reinforced Plastics in the Injection Molding Process
Currently, only specially treated and compacted carbon fiber recycles can be fed into the twin screw extruder. In this paper, different delivery forms of fibers are characterized in terms of the product quality. The differences between the fibers for twin screw extrusion is illustrated.
Comparison of Fiber Orientation Results of a Moldflow®-implemented pARD-RSC Model to µCT Scans
Fiber-reinforced polymers have gained popularity in various industries over the past years, as they allow the reduction of products' structural weight without compromising on performance. The material and mechanical properties of such polymer composites are mainly dependent on those of the fibers included in the polymer matrix. It is therefore crucial to be able to predict the fiber orientation in the injection-molded part during the design process. Simulation techniques offer an efficient and cost-friendly way to perform such predictions early on in the development process. However, accurate simulative predictions necessitate precise material models. Therefore, in this work, the prediction accuracy of three fiber orientation models are compared to experimental fiber orientation data obtained from high-resolution x-ray micro-computed tomography (µCT) scans for two different geometries. The models used to describe the fiber orientation in the Moldflow® simulation are a Solver API-implemented pARD-RSC model with shear-fitted parameters, an MRD model with Moldflow® default parameters and an RSC model with Moldflow® default parameters. Through the performed comparison, it was found that today’s state-of-the-art models are still unable to predict the fiber orientation for variant flow regimes and different part geometries accurately. This shortcoming was mainly highlighted for elongational flows.
Creating A Skin-Core Structure With Foamed Phenolic Resins In An Injection Molding Process
The research of foam injection molding for thermosetting materials is still in an early stage. Recent studies focused on the process of volumetric underfilling, but open pore structures and gradients over the flow path were obtained. This paper gives an insight into a novel process variant, which makes the production of skin-core structures possible. It is shown, how an expanding mold technique enables the production of components with a solid skin layer and a foamed core in an injection molding process with phenolic resins. In an experimental design, packing pressure time and mold temperature are identified as the main influencing parameters. Their impact on the skin layer’s height as well as the surface quality of the specimen are discussed. Finally, a model description of the processes leading to the formation of these foam structures is proposed.
Dynamic Variable Gate of Mold and its Application to Injection Molded Part Quality
As sensors evolve, their application has expanded. Mold related processes and technologies have become a focus of technology research and development. Mounting sensors in the mold cavity has become a trend in recent years. Since heretofore data has largely been limited to feedback data from the injection molding machine, control of the sensor data is the key to exploring the filling behavior of the molten melt in the cavity.In this study we created a dynamic variable-gate design in the mold. In combination with sensors to collect real-time data in the mold cavity during the injection stage, experiments were conducted to explore the course of shear heat and pressure drop generated by the melt passing through the gate when the gate thickness is varied. Therefore, the dynamic variable-gate design parameters such as gate thickness, advance delay time, and forward distance are discussed herein. To understand whether the gate thickness changes in the injection process, the influence of different parameters on the product shrinkage, product weight, and tensile strength are explored.
Enhanced Filling of Injection Molds By Microstructured Cavity Surfaces
The main objective of this paper is to evaluate the influence of microstructured injection mold cavity walls on cavity filling. Thermoplastic material has been tested with a variety of micro structured molds. The area density of the structures has been varied and the flow length of the plastic melt using constant filling pressure has been measured. Microstructures applied on one side of the injection mold significantly extend the flow length of the molten plastic. In addition, depending on the processing viscosity, there is an optimum structure area density for the longest possible flow paths. This knowledge is therefore valuable in production to realize longer flow paths with the same machine technology.
Experimental Wear Data Acquisition for Condition Monitoring in Injection Molding Machines
Condition Monitoring and Predictive Maintenance are big fields of research in the context of Industry 4.0. The ability of determining the state and predicting the lifetime of specific components can have a big economic impact. As datasets from production containing wear data are rare, it makes sense to generate this data in laboratory experiments. In this paper we present methods for implementing condition monitoring of injection molding screws and non-return valves. After developing key indicators, wear datasets are generated in laboratory experiments and the results are compared to the theoretical considerations.
Glass Reinforced PA 66 Compound with Improved Flowability for Thin Wall Applications
Glass reinforced polyamide compounds are widely used in various applications. Many of these applications require a material with high flowability to allow the molders to properly manufacture parts with thin walls and complex geometries. In this study, a flow enhancing additive is used to improve the flowability of a glass reinforced polyamide 66 compound. Flow characteristics of the new formulation were studied using various characterization methods. Test results showed that physical and mechanical properties were maintained very well while flowability of the modified formulation was enhanced significantly compared to the control material.
Hot Runner Molding of Bioplastics and Recyclates
The interest for molding of bioplastics and recyclates is continuously increasing, not only with increased awareness of sustainability issues but also in response to regulatory mandates to reduce environmental impact. Bioplastics and biopolymers have been successfully derived from renewable resources, however their commercial adoption remains hindered by the lack of processing experience. Degradation issues are a potential concern for manufacturers, especially for hot runner injection molding. In this work, the performance and thermal stability of three commercial biopolymers and a recycled resin were characterized and compared to a reference synthetic polypropylene. The results indicate that bioplastics can be readily processed by hot runner injection molding by following design and processing rules similar to those conventionally implemented for synthetic resins. Minor degradation and quality issues are solved by routine optimization of processing parameters.
In Situ Injection Molding Thermotropic Liquid Crystalline Polymer Reinforced Nylon 6 Composites With MWCNTS Filler
Thermotropic liquid crystalline polymer (TLCP), Vectra B, and nylon 6 (PA6) along with multi-walled carbon nanotubes (MWCNTs) forming multi-scale composites were processed via injection molding, yielding in-situ nanocomposites. Within this research, optimal injection molding processing conditions, in particular the temperature profile, for the production of MWCNTs filler reinforced in-situ composites were established. The optimized processing condition was aimed to minimize thermal degradation of PA6 and maintain mechanical properties of the composite. With the help of one percent addition of MWCNTs filler, the strength of the in-situ nanocomposites in the transverse to fluid flow direction was enhanced by 28%, while maintaining other tensile properties. MWCNTs also could help reduce the anisotropy in the nanocomposite. The experimental tensile results quantitatively followed the estimated values by the rule of mixture, which indicated PA6 had no thermal degradation.
Intelligent Hybrid Hot Runner System for Optimized Polymer Products
A novel “Rheo drop” concept is developed to advance the process of injection molding with hot runner systems. It controls shear rate during injection molding process in the hot drops, allowing us to process the material at lower temperatures since the viscosity can be reduced by increasing shear instead of increasing the temperature. Also, maintaining lower viscosity at the hot drop will prevent slug formation that causes incomplete filling defects when manufacturing thin walled parts. This innovative idea is suitable for temperature sensitive materials as they might degrade when subjected to excessive heat for longer periods. Analytical and experimental investigations were performed to validate the developed “rheo drop” concept. Simulations were performed using ANSYS fluent and the results confirmed that the concept was able to produce a sufficient amount of shear to significantly reduce the dynamic viscosity between injection molding cycles. To validate the concept experimentally, a hot runner mold was modified to retrofit the rheo drop technology. The results showed that the new concept was able to solve one of the molding significant issues, which is a defect that is caused by incomplete filling.
Low- and High-Pressure Foam Injection Molding of Polypropelene/Talc Through Chemical and Physical Foaming Agents
Recent research in the area of advanced polymer processing has demonstrated the potential of foaming agents to introduce additional functionality within injection molded components. In this research, Talc filled Copolymer Polypropylene (PP) ISO standard tensile bars were produced through low- and high-pressure foam injection molding (FIM). Two chemical blowing agents (CBA), Microcell® 548 and TecoCell® H1, in addition to N2, a physical blowing agent (PBA), were processed at both low-pressure and high-pressure configurations. The 2 foaming configurations were used to create parts with weight reductions of 12.6% and 8.8%, respectively. The samples foamed through CBAs produced stronger mechanical parts in both tensile and flexural modulus. Also, low-pressure foaming through CBA produced parts that had near-perfect surface finishes, matching that of conventional molding. High-pressure foaming through PBA showed an improved surface finish compared to low-pressure (through PBA) but was still inferior to that of the CBA foamed parts.
Machine Calibration Effect on the Optimization through Design of experiments (DOE) in Injection Mold
Quality issue is one of the most important concerns in injection molding. However, before executing mass production, how to retain good quality is one of the crucial factors in injection molding. To retain good quality, it is commonly using CAE to assist from original design to revision and to fabrication. However, even using CAE, it doesn’t guarantee the quality factors obtained from CAE can be applied to real experiments. Moreover, the design of experiment (DOE) method has been utilized into injection molding product development. Today, there are still some challenges when people using DOE in injection molding. In this study, we have designed one injection molding system to define quality factor based on a circle plate. Then, we have tried to perform a series virtual DOE testing for injection molding using CAE to optimize the process condition. Furthermore, we also performed real DOE experiment to verify the virtual DOE concept. Finally, we will discuss about the machine calibration effect on the accuracy of quality comparison. Results shows that before machine calibrated, both virtual CAE-DOE and real DOE optimization can provide better quality for injection parts. However, there is some difference between the virtual and real DOE results. To find out why the difference between the virtual and real DOE results happened, we have investigated the machine feature and tried to calibrate it. After machine calibrated, the difference between the virtual and real DOE results has been improved by 58%.
Method for Determining Cooling Time in Injection Molding Using Infrared Thermography
Injection molders face confusion about the best way to determine cooling time. Many methods exist to estimate cooling time, but disagreement among results and fundamental flaws create error that leads to extra work, long cycle times, and a loss of profitability for molders. This paper proposes a new method for determining cooling time at the injection molding machine using infrared thermography and DMA data to relate part ejection temperature to dimensional stability. Experiments showed evidence that dimensional stability is linked to material modulus, which would allow molders to choose cooling times based on required dimensional stability by relating measured ejection temperatures to specific modulus values using DMA data.
Predicting Fiber Orientation in Short Fiber Reinforced Injection Molding Process Using DEM
A new and efficient method using Discrete Element Method (DEM) to perform fiber orientation analysis for short fiber reinforced injection molding process is presented in this paper. This method uses a particle-based approach with one-dimensional two-node tracker particles that are convected by the flow field. Using this particle approach instead of solving a full tensorial equation yields higher accuracy and excellent computational efficiency. The underlying flow field for this analysis is computed using a FEM based simulation of the filling and packing phases of the injection molding process. Two case studies are presented to validate the implemented solution. The results show that the implemented solution is accurate and matches well with experimental data. Strengths and limitations of the model and the ongoing work to further improve this analysis are discussed.
Real-time PRESS MEAS during Plasticization and Injection Process and Its Effect on Part WT Variation
The development focus of the injection molding industry has gradually shifted from single-machine to factory-wide intelligence. Accordingly, a crucial research topic has emerged regarding the use of information collected by real-time sensors in injection molding machines to facilitate the integration of science-based software and machines and enhance product quality and machine productivity. In addition to equipment and manufacturing stability, product plasticization quality and characteristics are crucial factors affecting the establishment of a cyber-physical system for smart injection molding. The pressure-specific volume-temperature relationship is an essential attribute of polymers. The specific volume of a polymer varies with molding temperature or pressure. This causes difficulties in predicting the changes of polymer melts during injection molding, and therefore impedes control over product quality and precision. To address the aforementioned problem, this study adopted computer-aided engineering to perform analysis and experiments on the plasticization characteristics and behavior of plastic materials used in injection molding. A measurement system was established and installed on an injection unit to perform real-time measurement and record changes in the pressure of plastic melts during plasticization. The weight of the molded products was also recorded. Several process parameters were explored, including screw speed, back pressure, and melt temperature. The results indicated that (1) screw speed and back pressure exert considerable effects on barrel pressure and part weight; (2) overly fast screw rotation can cause the pressure in the compression section to exceed that in the metering section; and (3) back pressure exerts the greatest effect on barrel pressure and part weight.
Study On The Properties Of Microcellular Injection Molded Polyolefin/Polycaprolactone Composites
This study investigated the effects of polycaprolactone(PCL) loading on the morphology, tensile strength, and thermal properties of foamed injection molded PP and PPgMA composites. PCL is one of the biodegradable materials and can be used in heavy metal removal study. Results showed that PCL could increase tensile strength on PP but only small amount of it could enhance the tensile strength on PPgMA. PCL could affect the crystallization temperature and glass transition temperature both on PP and PPgMA. Storage modulus was enhanced by addition of PCL into PP and PPgMA.
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