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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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Injection Molding

In Situ Injection Molding Thermotropic Liquid Crystalline Polymer Reinforced Nylon 6 Composites With MWCNTS Filler
Jier Han, May 2020

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
Khalid Alqosaibi, May 2020

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
Gethin Llewelyn, May 2020

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
Rui-Ting Xu, May 2020

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
Eric Boud, May 2020

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
Ravi Mayavaram, May 2020

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
Wei-Huang Choong, May 2020

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
Chi-Chuan Hsu, May 2020

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.

The Challenge of Simulation For Ear-Flow Phenomenon In Injection-Mold Filling
Venny Yang, May 2020

Plastics applications are found in almost all areas of everyday living due to their versatility with an economically attractive choice in the manufacturing industry. Injection molding is the most common manufacturing process for producing plastic parts. However, there is a long-running problem requiring an urgent solution for the industry: to date, prior state-of-the-art predictive engineering tools have always provided unsatisfactory results regarding “so-called Ear-flow”, in which the advance of the flow front in the centre of the cavity is obviously slower than at the edges. Thus, the primary objective of this work is to simulate a reliable Ear-flow for neat polycarbonate (PC) material in injection molded disk via a new Moldex3D Flow solver coupled with the viscoelastic constitutive equation [U.S. Patent Pending in USPTO with Application No. 62/886,539 (2019)].

The Effect of Clamping Force on Product Quality: A Study on Platen Deformation
Wei-Jie Su, May 2020

The clamping force is a critical parameter to the stability of mold during injection molding process. An improper setting of the mold clamping force can adversely affect the service life of movable and stationary platens, tie bars, and molds. Thus, the clamping force is a key factor in product-quality consistency. This study bonded strain gauges to both sides of the movable platen to measure, in real time, strain changes in the platen under different clamping-force settings. The results were assessed using the corresponding cavity pressure and mold separation values to determine the molding clamping force’s effect on product quality (with respect to thickness, weight, and appearance). The findings indicated the following. (1) The mold clamping force is significantly correlated with cavity pressure, mold separation, and platen deformation. A low clamping force can cause mold separation to increase, which in turn results in greater platen deformation. (2) For the prediction of mold separation, strain gauges that are mounted on the movable platen can sufficiently replace displacement transducers that are placed within the molds. In other words, the condition inside the molds can be predicted using sensing devices outside the molds. (3) The analytic results for platen deformation and product quality indicate that an insufficient mold clamping force potentially results in excessive mold separation and platen deformation, causing flashing and an increase in product weight and thickness.

Towards Multi-Tiered Quality Control In Manufacturing of Plastics and Composites Using Industry 4.0
Saeed Farahani, May 2020

One of the most important topics in modern manufacturing, Industry 4.0 is quickly changing the way in which production lines in many industries operate. Industry 4.0 broadly refers to the connection of multiple manufacturing systems into a large system in which those individual systems communicate with one another. With systems connected in such a fashion, manufacturers can easily obtain actionable data from every aspect of their systems and use that data to improve their processes. Generally, Industry 4.0 technologies will vary significantly with application, and as a result, it can be difficult to develop an effective system from scratch. Given the increasing quality requirements demanded of the composites industry, particularly from automotive manufacturers, the development of an effective system to integrate data from the manufacturing process and apply it to advanced quality control methods is critical. Accordingly, we propose the concept of a multi-tiered system that combines machine data, in-mold sensors, external sensors, and a human component for use in plastics or composites manufacturing settings. Using this infrastructure, a multivariant analysis is first conducted to evaluate the advantages and limitations of each data sources in terms of determining process and part deviation. In the second study, the feasibility of developing a framework for monitoring quality of injected parts is investigated using a machine learning approach.

Workflow for Enhanced Fiber Orientation Prediction of Short Fiber-reinforced Thermoplastics
Susanne Kugler, May 2020

In this paper a workflow is proposed for an enhanced fiber orientation prediction in injection molding of short fiber-reinforced thermoplastics. The workflow is easy-to-use, as the final fiber orientation prediction is integrated into the commercial software Moldflow®. For a given material with polymer matrix P and a volume fraction x of fibers, four steps have to be performed: 1) Generating a representative volume element (in the following, referred to as cell) with volume fraction x and mean fiber length, 2) Shearing of the cell using a mechanistic fiber simulation, 3) Calculating the transient fiber orientation tensor and fitting macroscopic parameters and 4) Performing the fiber orientation analysis with the optimized macroscopic parameters in Moldflow®. Based on experimental data, the pARD-RSC model was selected as macroscopic simulation model. It was implemented in Moldflow® via the Solver API feature. The enhanced workflow is validated at the example of two industrial applications with different polymer matrices and different fiber volume fractions. With the proposed workflow, we observe equal or higher accuracy of fiber orientation estimation in comparison to Moldflow® fiber orientation models RSC and MRD.

The Evolution of Screw Design Technology for the Injection Molding Process - Part 1
Timothy W. Womer, November 2011

The screw is the heart of an injection molding process. Over the past several decades, screw design for the injection molding process has played a vital role in delivering high quality and value added plastics parts. That’s where the story begins.

‘Plug-and-Play’ Weight Reduction Solution by Hollow Glass Microspheres
Steve Amos | Baris Yalcin | Andrew D’Souza | I. Sedat Gunes, May 2011

Fillers have been in use since the early days of plastics. Today’s enormous growth of the polymer industry is due to the unique properties of fillers they impart to polymers. Glass bubbles (low density hollow glass microspheres) as fillers have been incorporated into thermoset polymers for decades. They are tiny hollow spheres and are virtually inert. These glass bubbles are are compatible with most polymers. Until recently, their use with thermoplastic polymers has been limited because of high rates of bubble breakage from the high shear forces to which they are exposed during such thermoplastic processing operations as extrusion compounding and injection molding. At issue has been the strength of the glass microspheres.

Aesthetics and Low-Cost Assembly Favour Film Insert Moulding
Prithu Mukhopadhyay, October 1999

It's the package that sells in the market. Decoration of injection moulded parts are no exception. Commonly known decorative methods are screen printing, pad printing, hot stamping or painting. However, to enhance productivity and achieving design freedom, new decorating methods such as Insert Moulding (IM) is gaining popularity.

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