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
Ultrasonic Velocity Measurements during Cure of Dicyclopentadiene (DCPD)
E.C. Brown, N. Corrigan, P.D. Coates, E. Harkin-Jones, R.J. Crawford, May 2004
Ultrasonic velocity measurements have been made during cure of DCPD. This material is under investigation for use in reactive rotational moulding in which the moulded part is manufactured using liquid DCPD and a layering technique. Each layer must be sufficiently cured to support the weight of subsequent layer addition. Ultrasound is being explored as a non-intrusive process-monitoring tool to detect mechanical property changes during early cure and enable use of the layering technique. Velocity is observed to decrease, simultaneous with temperature rise. Velocity is then observed to increase as cure progresses. The technique can distinguish variations in rate of cure.
Wireless Pressure Sensor for Injection Molding
David O. Kazmer, Robert X. Gao, Charles B. Theurer, Li Zhang, May 2004
Development of a wireless pressure sensor is motivated to reduce instrumentation and mold modification cost, improve lifecycle robustness, and thereby facilitate the widespread use of in-process sensing for process monitoring and control. In the presented design, the dynamic pressure in the mold cavity compresses a stack of piezoelectric rings, which generate a proportional electrical charge. Using an oscillator-based threshold switching device, the collected charge is relayed to an ultrasonic transmitter, which sends an acoustic signal at specific center frequencies to a receiver outside of the mold. Such a mechanical-electrical transduction process enables the online measurement of mold cavity pressure in a wireless fashion, without any external power supply.
Ultrasonic Cavity Sensors for Micro-Molding
S. Lee, D. Cuff, N. Huilgol, M. Chandra Sekhar, Charles L. Thomas, May 2004
This research investigates the application of ultrasound for monitoring conditions inside microcavities too small to be sensed using conventional sensors. An ultrasonic transducer was installed on an injection mold containing micro-cavities such that the sound pulse would strike the surface of the mold cavity and reflect back to the transducer. Changes in the intensity of reflected echoes are shown to be sensitive to the presence of polymer in the mold. By monitoring this changing reflected echo a signal is produced that is sensitive to conditions in the mold during processing. Two distinct advantages of the sensor are first, that it can sense conditions inside a micro-cavity, and second, that it can potentially do this from the outside of the mold plate, allowing an installation that requires no machining of the mold.
Controlling Melt Temperature in Injection Molding Using an Adaptive CFD Predictive Controller
Anna Healy, Rickey Dubay, Andrew Gerber, May 2004
Control of melt temperature in molding of high-precision components depends on the non-linear heat transfer and fluid dynamics behavior governing the process. Such systems are difficult to represent in a standard control strategy, especially if the material changes or set-point profiles are modified frequently in the process. This paper presents a strategy for combining computational-fluid-dynamics (CFD) with active process control to optimize controller performance. In this case the strategy is applied to control simulations of melt temperature in injection molding.
Infrared Melt Temperature Measurement: Effect of Filler Content on Penetration Depth
A.L. Kelly, E.C. Brown, P.D. Coates, May 2004
The effect of filler content on penetration depth of infrared temperature sensors is described, both in extrusion and in a specially designed imposed temperature gradient cell. White magnesium hydroxide and carbon black fillers were compounded with polyethylene in various levels and measurements made during extrusion and in the static cell. Filler content had significant effect on measured temperature in extrusion, causing changes in absorption coefficient of the compound. Effective penetration depths were quantified using the static gradient cell and emission spectra obtained from in-process infrared spectroscopy.
Real-Time Monitoring of Ethylene Vinyl Acetate Extrusion Using Process Spectroscopy
S.E. Barnes, M.G. Sibley, E.C. Brown, H.G.M. Edwards, I.J. Scowen, P.D. Coates, May 2004
Analysis of polymer production processes using spectroscopic and ultrasonic techniques is becoming more prevalent. Such at-process methods allow realtime chemical and physical information on melt characteristics to be obtained for process monitoring and control.This work will demonstrate real-time monitoring during extrusion of ethylene vinyl acetate (EVA) random copolymers with varying vinyl acetate (VA) content 1-40 % wt. In-line transmission near infrared and Raman spectroscopy has been used simultaneously with ultrasonic transit time measurements. The efficiency of the respective methods for determination of VA content is investigated and multivariate analysis of the spectroscopic data acquired is presented.
In-Line Color Monitoring during Polyethylene Extrusion: Reflectance Spectra and Images
Forouzandeh Farahani, Kyle Jeong, Saed Sayad, Stephen T. Balke, Felix Calidonio, Alex Rom-Roginski, May 2004
Two methods of monitoring the color of pigmented polyethylene during extrusion are being investigated. The first method utilizes a fiber-optic assisted charge-coupled-device (CCD) spectrometer to measure the color of the polymer melt. Highly precise L*a*b* values can be calculated from the reflectance spectra. The second method employs a CCD camera and RGB values are obtained for each pixel in the image of the extrudate. These RGB values track color changes but are sensitive to lighting.
Application of Ultrasound and Neural Networks in the Determination of Filler Concentration and Dispersion during Polymer Extrusion Processes
Zhigang Sun, Catalina V. Anghel, Jacques Tatibouët, May 2004
Mineral filler concentration and dispersion are important pieces of information for the production of mineral-charged polymers. In order to achieve timely control of product quality, a technique capable of providing real-time information on filler concentration and dispersion is highly desirable. In this work, ultrasound, temperature, and pressure sensors as well as an amperometer of the extruder motor drive were used to monitor the extrusion of mineralfilled polymers under various experimental conditions in terms of filler type, filler concentration, feeding rate, screw rotation speed, and barrel temperature. Then, neural network relationships were established between the filler concentration, filler dispersion index, and some of the process variables and the measurement data provided by the sensors. By using these networks and ultrasonic measurement data as input of the networks, we were able to achieve a better than 1 wt% average accuracy on the estimation of filler concentration and a better than 0.06 accuracy on the estimation of filler dispersion index. This study has demonstrated the feasibility of using ultrasound and neural networks for in-line monitoring of filler concentration and dispersion during extrusion processes of mineral-charged polymers.
Measuring Resin Temperature during Extrusion Using a Fluorescence Technique
A.J. Bur, S.C. Roth, D.W. Baugh, K.A. Koppi, M.A. Spalding, J. Gunderson, W.C. Buzanowski, May 2004
We have used a temperature sensitive fluorescent dye, doped into polycarbonate, to monitor the true resin temperature during extrusion processing. For this measurement, a fluorescent dye, perylene, was doped into the polycarbonate at very low concentration. We apply this measurement concept to extrusion processing by using an optical sensor that accesses the machine at standard instrumentation ports. The sensor has a confocal optics design that permits the measurement of temperature profiles. With the sensor looking over the screw of a single extruder, temperature profiles from the barrel wall to the core of the screw were obtained as a function of screw speed, screw design and melt flow index.
Effects of Processing Parameters & Wall Thickness on Core Geometry & Core Penetration for Co-Injected Parts
Stephen Johnston, Shawn Squires, May 2004
Co-injection is a specialized injection molding process in which two or more materials are sequentially or simultaneously injected into a mold. The resulting plastic part will consist of a skin of the first material covering a core made of the second material. This can allow for an ergonomic surface finish without jeopardizing mechanical strength. It also can help reduce material costs by allowing lower quality material to be incorporated into the core. The focus of this research was to determine the effect of processing parameters and wall thickness on the core geometry and penetration depth. With a better understanding of the co-injection process, it can be implemented for more parts and a potential cost savings can be realized.
Powder Metal Injection Molding - The Effect of Runner Design on Filling Imbalances at Different Fill Speeds
Andrew Schenck, Brian Martonik, May 2004
Imbalances occur in powder injection molding of multi cavity molds, which are sometimes opposite to the shear induced imbalances of conventional plastic materials. In a previous study it was found that melt rotation technology not only reduced imbalances, but also helped reduce differences between the mechanical properties of parts molded in multi-cavity molds. This paper presents the results of a study that expands on a previous work to include effects of fill rate, additional variations in runner geometries, and designs of melt rotation technologies for eliminating the variations.
Examination of Method for Diagnosing Mold Filling Imbalances in New Multi-Cavity Molds
Jaime A. Cypher, Amanda M. Neely, May 2004
During the startup and operation of new multicavity molds, it is expected that cavity-to-cavity filling variations will be found. This will occur despite the use of geometrically balanced runners. With cold runners, this imbalance is dominated by either steel variations in the mold, or shear induced variations developed in the runner. In order to correct the imbalances, it is important to be able to separate these two causes and to quantify their contribution. A method, here referred to as “The Five-Step Process” was developed for this purpose. This paper presents a study to determine how robust The Five Step-Process is in diagnosing steel variations in a mold.
The Effect of Runner Shape on Mold Filling and Product Variation
Amanda Neely, Mark Hennebicque, May 2004
In the plastics industry today it is generally accepted that full round runners provide the most efficient flow channel. However, when full round runners are implemented it is common for misalignment of the two halves of the runner to occur. This paper presents the effect that this misalignment has on mold filling and the resultant product. It is also common, in many instances and for many reasons, for other cross-sectional designs to be used. This paper also examines how subtle variations in runner design dramatically affects filling pressure, resulting in variations in molded parts. This study finds that there is a direct predictable relationship between the pressure drop through a runner and the ratio of the perimeter of the runner geometry to the cross sectional area of the runner.
Relationship of Predicted Shear Stress to Molded Plastic Parts
Marty W. Timm, Michael J. Couts, May 2004
Shear stresses developed during mold filling induce polymer orientation. This stress-induced orientation can be a significant contributor to a part’s residual stress, the development of anisotropic shrinkages and its tendency to warp. This paper presents a study that evaluates the relationship between the shear stress predicted from mold filling analysis software to its effects on a variety of different plastic materials. The study evaluates the impact of part wall thickness, melt temperature and fill rate. The study includes a variety of plastic materials, material fillers and reinforcements. Through a better understanding of the impact of predicted shear stress on different materials, a molder, or mold-filling analyst, will be able to minimize or avoid shear stress induced molding problems.
The Study of Process Stabilization and Consistency Using Pulse Cooling Compared to Cooling with a Thermolator
Trina R. Carl, Douglas French, Carl Caldwell, Eric D. Bowersox, May 2004
Injection molding requires a cooling phase within the cycle to cure the molten plastic that was just injected into a steel mold. The traditional method of cooling uses a mold cooling system to regulate the cooling. Pulse cooling, another method of cooling, is being studied to see how it compares in process stabilization and consistency to the traditional, constant flow, method of cooling.This study consists of an experiment using a constant flow cooling system to regulate cooling vs. using a pulse cooling system to regulate cooling. The data from the experiment is compared and the stabilization and consistency of the process using a pulse cooling system is compared to the standard cooling with constant flow.
Optimization of Extrusion Blow Molding Ovalized Tooling
James E.M. Lightfoot, Vincent A. Gallo, May 2004
Producing blow-molded bottles such as oval shaped cosmetics bottles requires the use of ovalized tooling. Currently the design of these dies is based the past experience. Simulation software can be used to eliminate extensive rework of the die, by allowing for the tooling design to be optimized without any steel being cut. The end result of this is a more uniform wall thickness distribution in the final product. 3D simulation software will be used to demonstrate its ability to construct and optimize the ovalizing of die and/or mandrel that could produce a parison for blowing oval shaped bottles. The results of this simulation can only be used with 3D simulation software.
Parison Verification of Parison Programming for Extrusion Blow-Molding Simulation Software
Benjamin Atkins, Nathan Lyons, May 2004
Using simulation software, a computer can help to gain a basic parison profile and in turn be an effective way to validate a design. When molding parts, by using parison programming, the operator has the ability to maintain a uniform wall thickness. The majority of users who do simulations assume a constant wall thickness and a uniform cylindrical shape for the parison. However, in real world applications this is not true, and two major occurrences, die swell and sag, are overlooked. The inability for the blow molding simulation software to recognize these factors, can lead to greater cost in terms of lost time.In an attempt to verify the accuracy of the software simulation programs, a 2D axisymmetric model of the parison was created and then compared actual parisons created on a blow-molding machine using parison programming. After completing this study, it is our hope that this will help the people who run the software to perform better simulations.
Evaluation of Geometric Effects for Extrusion Blow Mold Pinch-Off Design
Michael Butala, Ryan Reinhardt, May 2004
This study looks at secondary design parameters that affect the strength of extrusion blow molded parts at the pinch-off. The effectiveness of secondary parameters on weld strength creates a greater understanding of pinch-off design. Pinch-off design is critical in extrusion blow molding since it welds the parison together in the mold. Weld strength is important because the part could fail in application if the weld strength is poor.This is a continuation of a prior experiment, which concluded flash pocket dimensions were the primary contributor to weld strength. This study focused on the secondary effects while keeping the flash pocket constant. The bottles for this experiment were made out of HDPE. A two-level Design of Experiment (DOE) was implemented to examine the effect of the parameters on weld line strength.
HDPE Blow-Molded Bottle Pinch-Off Weld Strength of High Density Polyethylene at Various Molecular Weights
Mark K. Gutman, Justin M. Page, May 2004
This study focused on the weld strength of different materials in the pinch-off area of an extrusion blow-molded bottle. Various materials of different densities were run through an extrusion blow-molding machine. This study determined how weld strength at the pinch off was affected by the density of the material being processed. The pinch off is the portion of the mold that welds the ends, and at times the interior portions, of the parison as well as cut the excess flash to aid in removal. Having a strong weld was extremely crucial to overall bottle quality and was a direct result of pinch off design. The reason the pinch off has an effect on quality is due to the weld probably being the weakest part of the bottle and bottle strength is only as strong as its weakest point. Strength was a key issue in determining overall quality and the research performed allows for a direct correlation between strength and material grade.
Analysis of Weld Line Strength and Thickness for Extrusion Blowmolded HDPE Bottles
Sean Dubois, Colleen Janeiro, May 2004
One objective of any blow molder is to create the strongest weld possible at the pinch-off region. In order to do this, a clear understanding of how the material’s viscosity interacts with processing variables to produce a weld line of certain thickness and strength is required. By varying mold closing time, mold temperature and relief angle on two melt viscosity variations of high density polyethylene (HDPE) this paper will show a clear relationship between these variables. Thus, allowing for the blow molder to produce the strongest and most optimum weld line for HDPE blow molded bottles. In doing so, this article will show that a slow mold closing time coupled with a high mold temperature will produce the strongest and thickest weld lines for both vicosity variations of HDPE.
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