SPE Library
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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Conference Proceedings
Automatic Injection Velocity Initialization for Computer-Assisted Injection Molding Setup
David R Astbury, Alexander S. Bakharev, Russel Speight, May 2004
Modern systems for computer-assisted injection molding use data acquired from sensors and feedback from operators to setup the injection-molding process, to automate optimization of process parameters and to provide a statistical process control. A good initial starting point greatly streamlines injection molding setup and increases its robustness. Here we describe an algorithm for initial determination of injection velocity based on rheological calculations of the melt flow inside the mold cavity.
Geometric Variation of Micro-Features in Injection Molding Experiment
Sung K. Lee, Charles L. Thomas, May 2004
Micro features were produced on inserts for a macroscopic polymer injection mold. The inserts were produced using traditional machining and micro machining techniques. The inserts were installed and subsequent moldings were examined to measure the accuracy of replication of the micro features. The molding conditions were varied to identify the processing window available for accurate production of the micro features.
Flow Prediction in the Presence of Inserts for the Injection Over-Molding Process
Shishir Ray, Franco S. Costa, May 2004
Injection over-molding involves injection of molten polymer into complex cavities over solid inserts to form fabricated parts. This process is non-isothermal and the flow is strongly affected by the presence of the insert, and its thermal and mechanical properties. This paper compares the three dimensional flow simulation results of metal and polymer inserts and reviews their effects on filling pattern with experimental data. Furthermore, a two shot over-molding simulation is also presented.
A Genetic Optimization of Shrinkage by Runner Balancing
Kevin Alam, M.R. Kamal, May 2004
A new approach to runner balancing is proposed which identifies and deals with limitations associated with the traditional approach to runner balancing. The runner diameters are varied by a multi-objective genetic algorithm, which simultaneously optimizes the product shrinkage and cost. The results suggest that balanced runner systems, which exhibit large differences in cavity pressure, have lower product costs than systems characterized by similar fill times and cavity pressures. The optimization of the secondary runner lengths also reduced costs significantly.
Theoretical and Experimental Comparison of the Four Major Types of Mesh Currently Used in CAE Injection Molding Simulation Software
Matthew J. Jaworski, Zhongshuang Yuan, May 2004
Currently, CAE injection molding simulation software uses four major types of mesh for analysis. These four mesh types are beam (1D), mid-plane (2.5D), Dual Domain™ (modified 2.5D) and three dimensional (3D). Each mesh type is useful for simulating different types of plastic part geometries but also has its own limitations and assumptions. This paper will discuss the advantages and disadvantages of each mesh type through theoretical and experimental data.
Microcellular Injection Molding
Lih-Sheng Turng, May 2004
The paper reviews the processing advantages and challenges of microcellular injection molding and summarizes the recent research results obtained at the University of Wisconsin-Madison. The study emphasizes on how the process conditions and micro-/nano-scaled fillers affect the microstructure and mechanical properties of microcellular injection molded components. In addition, initial results of a novel co-injection molding process that combines the aesthetic and processing advantages of injection molding with the property attributes and benefits of microcellular plastics (MCPs) are presented.
Numerical Analysis of Microcellular Injection Molding
Sejin Han, R. Zheng, P. Kennedy, J. Xu, L. Kishbaugh, May 2004
This study presents a simulation model for the microcellular injection molding process in which supercritical fluid such as carbon dioxide or nitrogen is mixed with molten polymer and injected into the mold. Our model simulates the development of cells in the melt during injection molding. The effects of cell growth on material properties and flow have been investigated. Some simulation results such as melt pressure and final cell size distribution are compared with experimental results.
Structure Development and Mechanical Properties of Overmolded Parts
D.B. Tchalamov, A.M. Cunha, May 2004
Overmolding is a non-conventional injection molding method in which two or more polymers are introduced sequentially with a time lag into a special mold. In this study experimental design was employed for investigating retractable insert overmolding of two PP/HDPE combinations. Optical microscopy was used for evaluating structure development. Mechanical properties were examined through flexural and impact tests. The role of the interface of the two materials on the overall mechanical behavior was analyzed.
Effect of Overdrying Hygroscopic Resins and a Technological Solution for its Prevention
Suhas Kulkarni, David Hart, May 2004
Hygroscopic resins are dried before processing. Most polymers are blended with low molecular weight additives as heat stabilizers, processing aids and/or other specialty additives. If the resin is dried for an extended period of time, these additives tend to break down causing deterioration properties. Moisture can play an important role in the melt rheology. Experiments were done to study this effect with the help of thermal analysis and evaluation of physical properties. A technological solution to prevent overdrying is presented.
Thermoformability of ABS Grades
L. Pecora, A. Bardetti, D. Laroche, May 2004
Relationships between the rheological properties of different material grades with their processability are often difficult to make. In this work, a parameterization technique of the rheological properties is proposed to quantify the variations from grade to grade, within the same family. The impact of the identified parameters on the thermoformability of different ABS grades was investigated with the use of finite element simulation of the thermoforming process.
Production of Segmented Mold to Control the Distribution of Materials in the Thermoforming Process
Majid Tabrizi, May 2004
Control of temperature distribution throughout a segmented mold to reduce a part’s residual stress and improve material distribution has been studied. A segmented mold has been produced using a rapid mold making technique with in-cast cooling lines for a non-uniform cooling of the different segments of the mold.Polystyrene and polyvinyl chloride has been used to produce a number of parts for evaluation. The result showed a noticeable improvement in reduction of the internal residual stress with minimal effect on material distribution.
Influencing Wall-Thickness of Small Diameter Parisons
Walter Michaeli, Jens Grünewald, May 2004
Many complex blow-molded parts demand wall-thickness influencing systems to achieve a regular wall-thickness distribution in the part. For small parison diameters the standard systems can not be employed because of the high stiffness of the used deformable metal rings. A new die concept with turnable elliptical rings and an elliptical mandrel allows to change the flow channel height over the circumference and the parison swell behavior at the die outlet can be influenced.
Minimum Requirement for a Reliable Hot Runner Controller
Thomas P. Linehan, May 2004
There are many types of hot runner control designs. Some provide only basic features. There is a growing trend towards integrated or “GUI” (Graphic User Interface) styles of systems. However, despite the high-end features that many of these newer systems provide, they often have problems accurately measuring and therefore controlling temperature.This paper will discuss differences in system designs and how to detect the presence of potential problems.
Significant Factors on the Dimensional Accuracy of Fused Deposition Modeling
Robert C. Pennington, Nicole L. Hoekstra, Jeffrey L. Newcomer, May 2004
This project investigated the dimensional accuracy of parts produced using the rapid prototyping method of Fused Deposition Modeling. Parts with six different features were created on a Stratasys FDM2000 out of ABS and then measured with a Coordinate Measurement Machine and digital micrometers. An analysis of 12 different measurements on parts produced using FDM identified that part size, location in the work envelope, and envelope temperature had a significant effect on the dimensional accuracy of FDM.
The New Role of Moldmaking, with the Combination of Other Disciplines Form a Powerful New Role for Moldmaking in Today’s Manufacturing World
Thomas J. Diaz, May 2004
Presentation of the processes utilized to satisfy customer requirements for on time quality tooling while supporting a world class molding operation using internal and external resources in a very unique way in today’s competitive world of mold manufacture.
The Next Generation of Stainless Mold Steels for the Plastics Industry
Magnus Tidesten, Odd Sandberg, James Kaszynski, May 2004
Uddeholm Tooling in Hagfors, Sweden, has developed a new grade of stainless mold steel. This new material, called Stavax Supreme, has undergone extensive testing to evaluate its response to heat treatment, corrosion resistance and impact toughness.The data from laboratory and field-testing indicates a significant improvement in both the mechanical and physical properties over existing 420- type stainless mold steels. As a result, larger and more complex tools can now be manufactured from a fully hardened stainless mold steel.
New Developments in Unscrewing Molds
Ealias C. Joseph, May 2004
There are two new developments in unscrewing mold technology. The first development is an unscrewing system that is machine ejector actuated, eliminating the need for externally mounted hydraulic cylinders. This system was developed to suit clean-room applications for small diameter closures. The second development is a cavity-side unscrewing system utilizing a rotating cavity and is suitable for large diameter closures. This system was developed to suit multi-level stack molds.
Challenges in Characterizing Sealant
C.C. White, D. Hunston, May 2004
Sealant is one of the very few major consumer products valued primarily for its rheological and adhesive properties. While, these materials may appear to be simple elastic solids, upon further examination, their behavior can be extremely complex. In this research, reasonable simplifications are developed to model the non-linear viscoelastic properties of cured sealant. Also included are modifications of the traditional instrumental design to allow for high throughput evaluation of a cured sealant’s mechanical properties.
Rheological Properties of HDPE-Wood Composites
Karen Xiao, Costas Tzoganakis, May 2004
A comparison of the rheological properties of HDPE-wood composites as measured by both capillary and rotational rheometry was made. The blends studied ranged from 0% (pure HDPE) – 50% 40-mesh size maple wood flour. The elastic behavior of these materials was studied through the measurement of storage and loss moduli, creep data and Bagley correction factors. The Cox-Merz rule was found to be invalid for these HDPE-wood composites. The effect of processing behavior on the rheological properties was also investigated.
Yield Stress Measurements in Gels, Block Copolymer Systems and Suspensions
D. De Kee, May 2004
We will discuss a new slotted-plate device to directly measure static yield stresses of complex multiphase systems. Possible wall effects associated with our earlier yield-stress plate instrument have been minimized . Our new setup avoids the disadvantages of the vane instrument. Yield stress values on a variety of systems have been obtained and have been compared with the values obtained via a variety of other methods.
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