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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Theoretical and Experimental Comparison of the Four Major Types of Mesh Currently Used in CAE Injection Molding Simulation Software
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
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
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
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
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.
Effects of Design Solutions and Moulding Operating Conditions in Warpage
Injection molded parts with plane surfaces and complex flow are subjected to distortion depending on the mould geometry and general processing conditions. In this study, the effects of several mould and part design solutions were evaluated as well as the operating conditions of the injection molding machine. To examine warpage, the geometry of the plastic parts was defined and a modular mould was designed integrating pressure and temperature sensors. Experimental results, namely pressure, temperature and warpage values, were compared with those obtained from C-MOLD simulations.
Thermoformability of ABS Grades
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.
Practical Experiences with a System for In-Line Monitoring of Melting Spherulites in Semicrystalline Polypropylene Sheets
In thermoforming, it is found difficult to process Polypropylene if the heating control is based on measured sheet temperatures. It is shown that monitoring the melting of spherulites provides a better method. Testing is carried out using a novel device transmitting a laser beam through the PP-sheet. The scattering of the beam at spherulites within the sheet is indirectly measured via remaining beam intensity behind the sheet. With translucent Polypropylene, the melting of spherulites can be observed during heating.
Production of Segmented Mold to Control the Distribution of Materials in the Thermoforming Process
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
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.
Nozzle Melt Density Sensor Application for a Hot Runner
When a hot runner mold manifold transfers a melt “shot size” into the mold cavity, the hot runner system reduces the shot size, but it also adds a second heat history to the melt.Since temperature has a dynamic impact on the molding process, a melt sensor was developed to measure Volumetric-Pressure-Temperature change and, consequently, confirm the consistency of the thermal state.This sensor was installed into a machine nozzle, and the injected melt fill-and-pack “density” was profiled for consecutive cycles. The sensor application for a hot runner mold and resulting profiles are presented.
Minimum Requirement for a Reliable Hot Runner Controller
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.
Rapid Tooling - It’s Not Rocket Science
Rapid tooling (RT) pushed tool making into new areas. In the 1990s, rapid tooling using SLA, SLS, lasers, and other rapid prototyping (RP) technologies were the new wave. The promise of the processes threatened traditional machining methods, and mold-making shops pondered investment in exotic furnaces, raw materials and dedicated RP technicians.Looking at 2003, trends have changed. Rapid tooling is a reality, but the tooling is made using tied and true methods combined with better communication, verification of design and better machining. Rapid tooling changed the market. Now the question is what is the next step for RP and RT.
Significant Factors on the Dimensional Accuracy of Fused Deposition Modeling
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
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
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
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
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
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
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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