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

The Dependence of Cooling Channels System Geometry Parameters on Product Quality as a Result of Uniform Mold Cooling

Athanasios Bikas, Andreas Kanarachos, May 1999

The design and geometry of a cooling-channel system are significant factors for the injection molding process, as an optimized cooling system presumes high-quality molded parts at minimum cooling time. Significant quality characteristics of the molded part, depend on the geometry of the cooling system and on how heat is taken away by the cooling system per production cycle. A proper cooling system design results in a rapid but uniform and balanced cooling, and therefore decreases shrinkage, warpage, thermal residual stresses and maintains dimensional accuracy and stability. In the present paper the C-MOLD cooling analysis software is used to investigate systematically, based on the design of experiments" method the effect of the basic cooling system geometry parameters (diameter depth pitchnumber of cooling channels per manifold) on mold cooling quality. The mathematical model obtained from the above analysis can then be used to optimize the injection molding quality."

The Dependence of Cooling Channels System Geometry Parameters on Product Quality as a Result of Uniform Mold Cooling

Athanasios Bikas, Andreas Kanarachos, May 1999

The design and geometry of a cooling-channel system are significant factors for the injection molding process, as an optimized cooling system presumes high-quality molded parts at minimum cooling time. Significant quality characteristics of the molded part, depend on the geometry of the cooling system and on how heat is taken away by the cooling system per production cycle. A proper cooling system design results in a rapid but uniform and balanced cooling, and therefore decreases shrinkage, warpage, thermal residual stresses and maintains dimensional accuracy and stability. In the present paper the C-MOLD cooling analysis software is used to investigate systematically, based on the design of experiments" method the effect of the basic cooling system geometry parameters (diameter depth pitch number of cooling channels per manifold) on mold cooling quality. The mathematical model obtained from the above analysis can then be used to optimize the injection molding quality."

A Comparison of Different Strategies for Injection Filling Velocity Control

Yi Yang, Furong Gao, May 1999

Injection velocity during filling stage was experimentally controlled using different control algorithms, from simple open-loop control and Proportional-Integral (PI) closed-loop control, to more advanced strategies such as Self-Tuning Regulator (STR), fuzzy control and Generalized Predictive Control (GPC). It is shown that the advanced control can effectively overcome the non-linear and time-varying characteristics of the filling velocity. The advantages and drawbacks of each strategy are presented and experimentally illustrated. The use of advanced control strategies is shown to be necessary for accurate control of the injection velocity with good repeatability.

Reduced Time to Market Using Blow Molding Simulation Software

Curtis S. Randall, David P. Prior, May 1999

Speed to Market. The cliché is well entrenched in today’s business jargon. When spoken, we nod our heads fully cognizant of the relentless pressures the concept conjures up. To deliver fresh new products in lightning strike fashion. That directive is the paramount force driving engineers and designers to endlessly search for the latest tool that will circumvent time, provide greater precision and produce that widget with less cost. Technical Blow molding is considered by many as much a black art as either science or engineering and rightfully so. We often look to the technician who runs the machine day in and day out for advice. Perhaps we consult a fellow employee who knows the most about what did or didn’t work in their world of experience. In both cases, we’re trying to get a feel of whether or not that new design is moldable. More often than not, we fall back to what is safe because we no longer have the luxury of additional time to debug or break in a truly new idea on the molding floor. A new tool has arrived that will change how we approach blow molding. This paper will examine an actual case study on how Fisher-Price, Inc. was able to drastically reduce product debug time by utilizing BlowView® Blow Mold Simulation Software developed by the Industrial Materials Institute of the Canadian National Research Council.

Effects of Molecular Structure on the Rheology and Processability of High Density Pokyethylene Blow Molding Resins

Alfonsius B. Ariawan, Savvas G. Hatzikiriakos, Henry Hay, Shivendra K. Goyal, May 1999

The influence of molecular structure on the rheology and processability of HDPE blow molding resins is studied. Experiments were conducted using capillary and extensional rheometers, a melt indexer and a blow molder unit. Twenty four resins were analyzed in terms of their shear flow and extensional properties, extrudate swell characteristics, and melt strength. The studied samples were produced using a variety of manufacturing technologies and had varying molecular weight characteristics. From the results, the influence of molecular structure on the rheological properties was determined. Furthermore, to assess resin processability, pillow mold (blow molding) experiments were performed. The implications of rheology on processability (parison sag and weight swell) are also discussed.

Determining Etch Compensation Factors for Printed Circuit Boards

Anthony DeRose, Richard P. Theriault, Tim A. Osswald, Jose M. Castro, May 1999

A model has been developed to simulate the progression of material properties and residual stress development during the processing and etching of metal-clad, multi-layered, fiber mat reinforced, thermoset resins used in the printed circuit board industry. The simulation predicts the dimensional movement of the laminates during the manufacturing stages. This information can then be used to prescribe compensation factors to the artwork during the etching process. Predicting the residual stress, shrinkage, and warpage of these systems can lead to a minimization of the size of the circuit patters while decreasing the number of failures.

Modeling and Simulation of Mechanical Properties of PP According to the Thermal History Imparted

C. Albano, R. Sciamanna, R. Gonzalez, May 1999

The object of this investigation is to design software, along with the corresponding experimental methodology, that allows characterizing and/or predicting the mechanical behavior of semicrystalline plastic materials, such PP, based on the crystallinity developed during the manufacturing process used. The experimental temperature and crystallinity profiles are theoretically reproducible by means of the simulation program developed. The curves obtained for the various properties indicate that there is a high degree of proportionality between crystallinity and mechanical properties.

Study of Staggered Flow Fronts with Applications to Sensor-Based Control

S.M. Walsh, R.V. Mohan, May 1999

The present study examines several issues of relevance in the understanding and development of techniques for characterizing and controlling flow fronts developed in the VARTM (Vacuum Assisted Resin Transfer Molding) process. A sensor-based control system was used to selectively and autonomously compensate for lagging flow fronts resulting from permeability variations in the constituent preform. The fundamental control objective was to thoroughly impregnate the entire fibrous preform in a minimum amount of time, subject to minimizing the flow lag" induced by dissimilar preform peremeabilities."

Composite Material for Rapid Tooling Produced by High Speed CNC Machinery

Mahesh A. Kotnis, May 1999

Rapid Prototyping (RP) and Rapid Tooling (RT) have become increasingly important processes for fast to market" product development. Two RT approaches are to produce molds from (1) RP patterns and (2) CAD data using additive or subtractive methods. This paper discusses the second approach based on a new moldmaking material that can be CNC machined at very high speeds. The new composite material demonstrates the compressive strength thermal resistance and thermal diffusivity required for the injection molding of production grade thermoplastics to produce hundreds of dimensionally accurate prototypes under normal injection pressures and temperatures."

DOE & Decoupled Molding Part I: Process Centering and Validation from the Plastic's Point of View

Robert G. Launsby, Michael R. Groleau, Tom Wilmering, Rodney J. Groleau, May 1999

Frequently, injection molders approach experimental designs from the perspective of the settings on the molding machine, sometimes resulting in sub-optimal or misleading results. Further, when the resulting process is validated, it is typically done under short term sources of variation. This frequently proves to be a poor evaluation of the true long-term capability of the process. A new approach to centering and validating processes is proposed and a model study is presented for illustration. Here, the experiment is conducted around the fundamental variables that affect the part inside the mold, using a physical model" that acknowledges the unique physics of the injection molding process. Next the data is correlated with fundamental process variables allowing causal relationships to be established. Finally during validation primary sources of long-term variation are introduced into the capability study."

DOE & Decoupled Molding Part I: Process Centering and Validation from the Plastic's Point of View

Robert G. Launsby, Michael R. Groleau, Tom Wilmering, Rodney J. Groleau, May 1999

DOE & Decoupled Molding Part II: Correlation of Cavity Pressure with Part Characteristcs for Automated Parts Containment

Michael R. Groleau, Robert G. Launsby, Rodney J. Groleau, May 1999

As more molders face pressure to reduce costs of quality, many are turning to cavity pressure monitoring to automate part segregation. Here, abnormal parts are automatically rejected in real time using alarm levels placed around key cavity pressure measures. However, few techniques are available to determine which measures to monitor and what alarm levels to set for each of them. A new, systematic technique has been developed to assist molders in the selection of appropriate measures and alarm levels. Using data taken during a DOE based tryout, correlations are made between cavity pressures and key part characteristics. For metrics which show the best correlations, alarm limits are set based on part specifications. In this paper, a model study is presented to illustrate the application of these techniques.

Dramatic Changes in Glass Filled Polyphenylene Sulfide (PPS) via Variations in Maximum Fill and Packing Pressures, Injection Rate and Melt Temperature

J.D. Ratzlaff, J.R. Wareham, May 1999

Process conditions in injection molding can dramatically change the mechanical properties of glass filled PPS. The parameters studied included maximum cavity-fill pressure, packing pressure, injection velocity, and melt temperature. This study utilized advancements in cavity pressure measurement and switching by cavity pressure to control the injection fill stage. Also, an easy designed experiment was used that allows for practical, quick, and reliable testing of part properties that can be applied to future part performance studies. Due to many mechanical variables, this study focused on tensile properties.

New Methodology for Determining the Blow Mouldability of Engineering Resins for Automotive Applications

A. Garcia-Rejon, M. Carmel, R. Ramanathan, May 1999

For a resin to be successful in a blow moulding application, it has to comply with a set of characteristics known as a whole as the material's blow mouldability". This concept includes the parison swelling behaviour (both in diameter and thickness) and the resistance of the melt to extension (melt strength). This paper outlines a new methodology geared towards the establishment of relationships between relevant rheological properties and key processing material behaviour parameters (swell and sag) governing the blow moulding process. The technique has been applied to the intermittent extrusion of a PC/ABS blend (PULSE™). Several processing parameters such as drop time extrusion temperature and die gap were studied."

Injection/Stretch Blow Moulding of PET/LCP Blends for Better Product Performance

A. Garcia-Rejon, K.T. Nguyen, W. Michaeli, L. Morich, G. Schmidt, R. Lusignea, May 1999

PET plastic containers are mainly manufactured by the injection stretch blow moulding process. Their main advantages compared to glass containers, are their low cost of production, lighter weight and high impact resistance. However, the growing demands on beverage containers regarding barrier properties and hotfill ability have surpassed the PET limits in applications such as beer bottles, fruit juice containers, etc. The aim of this work is to examine if PET/LCP blends moulded on a one-step injection stretch blow moulding can produce bottles that fulfill the requirements of barrier and mechanical properties and hotfill ability. The results are interpreted based on the flow behaviour and microstructure characteristics of the materials.

Microstructure Development during the Injection Moulding of PET/LCP Blends

E. Turcott, K.T. Nguyen, A. Garcia-Rejon, May 1999

For several years, plastics processors have been blending two or more generally incompatible materials in order to improve physical or mechanical properties. Depending on the degree of compatibility and thermomechanical history during processing, various goals may be attained: easier processing, improved mechanical (modulus, impact strength), thermal and barrier properties. Polyethylene terephthalate (PET) enjoys wide success in industrial applications because of its outstanding mechanical, optical and barrier properties. However, the growing demands of the electronics and automotive sectors have surpassed the PET performance limits. With its outstanding barrier properties as well as mechanical properties even at high temperatures, LCP's are potential candidates as a blend component.

Transverse Permeability of Direct Glass Rovings

P.J. Bates, Danny Taylor, Michael Cunningham, May 1999

Rovings are used in a variety of polymer processes such as filament winding and compression molding. In all these processes, impregnation of the roving monofilament bundle by the liquid polymer is essential. Modeling polymer impregnation requires an estimate of the transverse Darcy's Law permeability. This study measured the transverse permeability of 2400 tex glass rovings as a function of applied compressive stress, monofilament diameter, roving thickness, fluid velocity and viscosity. The permeability was observed to depend strongly on the compressive stress, and hence void fraction. The permeability was independent of the monofilament diameter, roving thickness, fluid velocity and viscosity. Results are presented using a simple model that accounts for roving void fraction inhomogeneities.

Finite Element Modeling of the Plug-Assisted Thermoforming Process

J.F. Lappin, E.M.A. Harkin-Jones, P.J. Martin, May 1999

In the production of food packaging using the plug assisted pressure thermoforming process it is desirable to optimize costs and product properties through efficient distribution of material. Typically in industry conditions for forming are obtained by trial and error which can be very inefficient. In this paper the development of a finite element model of the process is described. Modeling was carried out using a commercial finite element package and the model encompasses both 2D axisymmetric and more complex 3D geometry. Material behavior is simulated using a viscoelastic model based on data obtained from various material tests.

Crystallization of Isotactic Polypropylene: Pigment, Nucleating Agent and Recycling Effects

Y. Mubarak, E. Harkin-Jones, P. Martin, M. Ahmad, May 1999

In order to produce thermoformed products of consistent quality, an understanding of the effect of material and process parameters on end part performance is necessary. In this investigation the effect of pigment, nucleating agent, and recycling regrind on the nucleation of homopolymer isotactic polypropylene have been studied. Differential Scanning Calorimetry was used to reveal the effect of these additives on the crystallinity, type of crystals, crystallization and melting temperatures at different cooling rates. It has been found that percentage cystallinities were increased as the concentration of the nucleating agent and first and fifth generation regrinds increase up to the saturation level. Although more hexagonal ? crystals were formed by increasing the concentration of the pigment, the enthalpy of fusion was decreased.

Influence of Extrusion Parameters on Polypropylene Sheet for Use in Thermoforming

G.W. Harron, E.M.A. Harkin-Jones, P.J. Martin, May 1999

The quality of extruded sheet for use in subsequent thermoforming operations may be defined in terms of its resistance to sag, low and consistent shrinkage, tensile properties and overall consistency of these properties with time. The sheet extrusion process has many variables such as melt temperature and output rate that may influence the properties of the sheet and it is the objective of this work to identify the critical variables in the process. To achieve this objective a series of experiments were conducted using a statistical design of experiments methodology. This investigated the effects of MFI, Melt Temperature, Chill Roll Temperature and Line Speed on the properties of the extruded polypropylene sheet which are of importance in the future thermoforming process. The sheet properties investigated included tensile properties, crystallinity, sheet sag and shrinkage. The main findings of the study were that melt temperature had the main effect on the shrinkage in the machine direction, while the chill roll temperature and line speed had the main effects on the tensile properties. Sheet sag was found to be greatest at the lower MFI value, which correlated to the lower levels of crystallinity of the as made sheet.