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Conference Proceedings
SIMULATING THE DEFORMATION BEHAVIOR OF THERMOPLASTIC PARTS UNDER THERMAL AND MECHANICAL LOADS
Yunior Hioe, Keh-Chyou Chang, Maria G. Villarreal, Jose M. Castro, May 2010
During service, thermoplastic parts are often subject to a combination of thermal and mechanical loads. Especially the temperature has a great influence on the stiffness and the specific volume. Consequently the thermal exposure has to be considered during the design process of thermoplastic parts. This paper describes the modeling of the temperature-dependent viscoelastic material behavior. Because the determination of the required thermal and mechanical properties is cost- and time-intensive, a procedure is elaborated to depict the temperature-dependent long-term behavior on basis of short-time tensile tests. Finally the model is evaluated in a comparison with experimental results.
PREDICTING THE CYCLE TIME IN INJECTION MOLDING AS A FUNCTION OF THE FROZEN LAYER THICKNESS
Yunior Hioe , Keh-Chyou Chang , Maria G. Villarreal , Jose M. Castro, May 2010
In the current economic market, production efficiency is critical if manufacturers are to remain competitive. The largest part of the cycle in injection molding is the cooling time. Thus for injection molders, to be successful, it is extremely important that they minimize this part of the process without adversely affecting part quality. Predicting the minimum safe cycle time in injection molding is complicated by the cyclic nature of the process. The mold thermal state changes with continuous molding until a quasi steady state is achieved.In this work, we evaluate the minimum frozen layer thickness required before the part can be demolded and how the growth of this frozen layer is affected as the mold thermal state changes with continuous molding cycles. Experiments are used to relate the minimum frozen layer thickness to dimensional stability and to select an ejection criterion in order to obtain a minimum safe cooling time
A STUDY ON MATERIAL DISTRIBUTION AND MECHANICAL PROPERTIES IN CO-INJECTION MOLDING
Yottha Srithep , Bob Miller , Rachmat Mulyana Maria G. Villarreal , Jose M. Castro, May 2010
In the co-injection molding process, sometimesreferred to as sandwich molding, two different polymermelts are either simultaneously or sequentially injectedinto a mold to form a part with a skin/core structure. Coinjectionmolding offers the flexibility of using the bestproperties of each material to reduce material cost andpart weight. Particularly, it allows, the use of recycledmaterial in the core without an adverse effect on surfacequality. The properties of a co-injection molded productdepend on the individual properties of the skin and corelayers, and the skin/core volume ratio. This paper presentsa study of the effect of molding parameters on materialdistribution and mechanical properties of co-injectionmolded plates. Two virgin materials were triedpolypropylene (PP), and thermoplastic polyolefin (TPO)as well as grinded TPO from plastic bumpers.
MODELLING THE STRUCTURAL PERFORMANCE OF STRETCH-BLOW MOULDED PET BOTTLES
Walter Michaeli, Thorsten Leopold, May 2010
The mechanical properties of PET bottles are significantly affected by the process. In order to precisely model the structural performance of these bottles, the wall thickness and the process dependent material properties have to be considered. This paper describes an approach to combine the structural analysis and the process simulation. The wall thickness distribution and the local stretch ratios of the blown bottle are calculated by a process simulation and are then transferred to the structural analysis. Thereby, the stretch ratios are correlated with stretch ratio dependent material properties. In cooperation with Nestl?? Waters M.T., Vittel, France, the approach is applied on an empty and filled 0.5 litre PET bottle. The investigations point out that the accuracy of the structural analysis is significantly improved by applying the integrative approach.
NUMERICAL SIMULATION OF THE FAILURE BEHAVIOR OF PE PRESSURE PIPES WITH ADDITIONAL LOADS
Pavel Huta? , Martin Šev?ík , Luboš Náhlík , Ivaylo Mitev , Andreas Frank , Gerald Pinter, May 2010
Using linear elastic fracture mechanics concepts a simulation methodology for the assessment of internally pressurized pipe lifetimes was developed. The concept is based on the numerical calculation of stress intensity factors for pipes under different loading conditions and on using experimentally generated creep crack growth kinetics for lifetime calculations. Comparison of simulated lifetimes with experimental data from tests with internally pressurized pipes proved the principal applicability of the concept but also identified major parameters affecting pipe lifetime.
NUMERICAL SIMULATION OF THE FAILURE BEHAVIOR OF PE PRESSURE PIPES WITH ADDITIONAL LOADS
Pavel Huta? , Martin Šev?ík , Luboš Náhlík , Ivaylo Mitev , Andreas Frank , Gerald Pinter, May 2010
Using linear elastic fracture mechanics concepts a simulation methodology for the assessment of internally pressurized pipe lifetimes was developed. The concept is based on the numerical calculation of stress intensity factors for pipes under different loading conditions and on using experimentally generated creep crack growth kinetics for lifetime calculations. Comparison of simulated lifetimes with experimental data from tests with internally pressurized pipes proved the principal applicability of the concept, but also identified major parameters affecting pipe lifetime.
DEVELOPMENT OF A PERMANENT PLASMA-INDUCED RELEASE COATING AS A SURROGATE FOR NON-PERMANENT RELEASE AGENTS
Kun Chang Lin, Ming-Tsai Liang, Chia-Hsun Chen, Chen-Feng Kuan, Hsu-Chiang Kuan, May 2010
In the production of polyurethane parts the use of nonpermanent release agents is still inevitable. The regular mold-cleaning of residua of the release agent reduces the efficiency of the production process considerably. This paper describes the development of a permanent plasma-induced release coating with high durability for the series production of PU-parts as a surrogate for conventional non-permanent release agents. Basis of the project is a plasma-polymeric gradient layer with highly crosslinked siloxane-compounds for the mechanical strength of the coating and a high density of methyl groups towards the PU-sided surface for excellent release properties.
VALIDATION OF AN ACCELERATED FRACTURE MECHANICS EXTRAPOLATION TOOL FOR LIFETIME PREDICTION OF PE PRESSURE PIPES
Philipp Liedl Guenter Haag, Gunter Fischer, Jeff Lambing, May 2010
For a fracture mechanics lifetime assessment of pressurized polyethylene (PE) pipes the knowledge of the material specific creep crack growth (CCG) kinetics is essential. As testing of CCG with common test methods is not possible in feasible times, an accelerated extrapolation procedure based on fatigue tests with cracked round bar (CRB) specimens was developed previously. Within the present work this test procedure was used to characterize CCG of a PE material at elevated temperatures of 60?øC. In combination with a numerical simulation model for pressurized pipes, lifetimes were predicted and correlated to real pipe failure times of the same material.
SAVING MONEY USING INTELLIGENT PROCESS OPTIMIZATION SOFTWARE
Philipp Liedl , Guenter Haag , Gunter Fischer , Jeff Lambing, May 2010
Looking at the increasing quality requirements and the potential for time and cost savings in almost all injection molding processes the classical way of optimizing a process has to be reviewed. New and innovative software solutions for process optimization and quality forecasting therefore plays an important role and helps to answer common questions to the shop floor managers: Is the current machine setting the best one in terms of cycle time and process capability? Is there a potential to save time material or energy? Which machine parameters have the highest influence on the quality? A new software solution using self generating neuronal networks now respond to these questions and supports users without requiring a deep mathematical background. It offers a pragmatic solution to be used by all participants on the shop floor level. Practical experience confirmed that on average 10% reduction in cycle time can be achieved.
SAVING MONEY USING INTELLIGENT PROCESS OPTIMIZATION SOFTWARE
Philipp Liedl , Guenter Haag , Gunter Fischer , Jeff Lambing, May 2010
Looking at the increasing quality requirements and the potential for time and cost savings in almost all injection molding processes the classical way of optimizing a process has to be reviewed. New and innovative software solutions for process optimization and quality forecasting therefore plays an important role and helps to answer common questions to the shop floor managers: Is the current machine setting the best one in terms of cycle time and process capability? Is there a potential to save time, material or energy? Which machine parameters have the highest influence on the quality? A new software solution using self generating neuronal networks now respond to these questions and supports users without requiring a deep mathematical background. It offers a pragmatic solution to be used by all participants on the shop floor level. Practical experience confirmed that on average 10% reduction in cycle time can be achieved.
STRUCTURAL ANALYSIS OF SEMI-CRYSTALLINE THERMOPLASTICS WITH REGARD TO THE LOCALLY DISTRIBUTED MATERIAL BEHAVIOR DUE TO VARYING INNER PROPERTIES
Natti S. Rao, Ranganath Shastri, May 2010
During its manufacturing cycle a thermoplastic injection-molded part can be exposed to heat at various times. This has an influence on the inner and therefore on the mechanical properties of the part. Regarding these effects an integrative simulation approach has been developed at the Institute of Plastics Processing at RWTH Aachen University. It includes the development of a user-defined non-linear material model which takes into account the local distribution of the inner properties depending on the processing conditions and heat treatment. This paper deals with the main aspects of the material model and with the linking of the process simulation and the structural analysis using a universal data format.
PERFORMANCE OF A HELIBAR® EXTRUDER USING A GROOVED BARREL
Chan I. Chung , MoonKi Choi , Lee Gunning , Eberhard Gruenschloss, May 2010
A new type of single-screw extruder with grooved barrel in the feeding and the melting section called “HELIBAR®” was successfully introduced in recent years. The grooved feeding section is typically cooled passively by ambient air. The performance of a 35 mm D. 34 L/D HELIBAR was evaluated by running PP PC and ABS in pellet form HMW-HDPE in powder form and HDPE as a blend of pellet and regrind. One barrier-type single-stage screw was used for all resins. The output rates of this extruder were 3-4 times higher than those expected for the same size extruder with smooth barrel while the specific output rates (output rate per RPM) were more than twice and virtually independent of screw speed or head pressure. Furthermore this extruder had excellent stability of the output rate and the melt temperature.
PERFORMANCE OF A HELIBAR?? EXTRUDER USING A GROOVED BARREL
Chan I. Chung , MoonKi Choi , Lee Gunning , Eberhard Gruenschloss, May 2010
A new type of single-screw extruder with grooved barrel in the feeding and the melting section, called 'HELIBARR', was successfully introduced in recent years. The grooved feeding section is typically cooled passively by ambient air. The performance of a 35 mm D., 34 L/D HELIBAR was evaluated by running PP, PC and ABS in pellet form, HMW-HDPE in powder form, and HDPE as a blend of pellet and regrind. One barrier-type single-stage screw was used for all resins. The output rates of this extruder were 3-4 times higher than those expected for the same size extruder with smooth barrel, while the specific output rates (output rate per RPM) were more than twice and virtually independent of screw speed or head pressure. Furthermore, this extruder had excellent stability of the output rate and the melt temperature.
DEVELOPMENT OF AN ADAPTIVE PROCESS OPTIMIZATION OF HOT-TOOL WELDING USING AN INNOVATIVE ACTUATION CONCEPT
Yogesh Vakharia, May 2010
This paper is a continuation of work presented at ANTEC 2009 [5]. It looks into the initial steps of the development of a self-optimizing hot-tool welding machine. A new machine concept permits the specimen to be pulled in a direction opposite to the joining direction. Using this feature it is possible to assess the strength of the weld directly at the hot plate welding machine. The strength was measured while the material was still in the molten state. In order to use these results for a selfoptimization it was necessary to establish a correlation between the short-time strength of the parts in the cooled state and their short-time strength in the still molten state. Using this concept, the control system of the welding machine can be adapted to find an optimum processing window with just a few test welds. The results show that the optimum of the parameter settings can be defined by measuring the tear forces on the welding machine. Based on these results a self-optimization and quality assurance during the running hot-tool welding process can be developed and tested.
WHY GRADIENT COPOLYMERS MAKE BETTER COMPATIBILIZERS OF IMMISCIBLE POLYMER BLENDS THAN BLOCK COPOLYMERS: DETERMINING CRITICAL MICELLE CONCENTRATIONS OF COPOLYMER IN HOMOPOLYMER
Robert W. Sandoval , Daniel E. Williams , Golnar Doroudian , Christopher L.H. Wong , Jungki Kim , Connie B. Roth , John M. Torkelson, May 2010
A fluorescence technique is used to determine critical micelle concentrations (CMCs) of styrene-containing block and gradient copolymers dispersed within a homopolymer. Block copolymer composition and molecular weight are varied to determine what factors impact the CMC. Gradient copolymers are shown to have higher CMCs than block copolymers due to the gradient in comonomer composition along the copolymer backbone. Gradient copolymers can be more effective as compatibilizing agents, as they are less likely to be trapped within micelles upon melt processing
IN-MOULD LAMINATION OF METAL SHEETS WITH INTEGRATED FORMING FOR METAL DECORATED PARTS
Musa R. Kamal, Jingsong Chu, Salim Derdouri, Andy Hrymak, May 2010
For high-class applications (e.g. automotive interior) metal decorated plastic parts impress the customers with a metallic look and cool-touch haptics. Producing these parts has been a highly complex process. The in-mould lamination process of metal sheets allows a shortened process chain. In the process the injected melt adheres to a primer system on the metal surface. Furthermore the pressurized melt causes a forming of the metal sheet. This new technology enables a one-step production of metal decorated plastic parts. This paper describes design principles for metal (stainless steel and aluminum) decorated parts first. Then the effects of the injection molding process parameters on the forming quality are shown. An approach to simulate the forming process is presented and evaluated by test results.
THE MORPHOLOGY OF MICRO-INJECTION MOLDED POLYOXYMETHYLENE
Musa R. Kamal , Jingsong Chu , Salim Derdouri , Andy Hrymak, May 2010
A micro-injection molding machine was used to obtain micro-moldings of high density polyethylene, polyoxymethylene, and polycarbonate, in order to study the effects of processing conditions on the microstructural characteristics and mechanical properties. The samples were microtomed and examined using a polarized light microscope for evaluation of morphology. Various microstructural features, such as morphological layer thickness and crystalline polymorphs, were observed and analyzed, in light of the thermo-mechanical history. These features were also correlated with both macro and local mechanical properties.
INTERNAL MIXERS: A NEW APPROACH TO COMPOUND TPE
E. Soos Takacs, S. M.Tanu Halim, J.Vlachopoulos, R.T. Fell, H.G. Diem, May 2010
The generation of process knowledge for the discontinuous compounding of TPE in internal mixers enabling companies of the rubber industries to produce TPE with defined material properties is the aim of the presented project. The properties of TPE strongly depend on its morphology. To adjust the material properties during the mixing in an internal mixer, it is important to understand how the morphology is influenced. Therefore, the melting of the thermoplastic phase and the dynamic vulcanisation of the elastomeric phase are investigated in dependence of the process parameters. The morphology of the TPE is then correlated with the material properties.
SWITCHOVER CONTROL IN THE POLYMER INJECTION FORMING PROCESS
Ruggero Baesso , Giovanni Lucchetta, May 2010
Polymer Injection Forming (PIF) is a new technology to manufacture sheet metal/polymer macro-composite components in a one-operation production process. During the process a metal blank is formed inside an injection mold by means of the pressure of the molten polymer.Changing from velocity control to pressure control just before the mold is filled is a common practice in the traditional injection molding process. In this paper different switchover strategies for the PIF process were investigated. Shot to shot consistency obtained by these methods was evaluated by means of process variations in terms of cavity melt pressure.
EVALUATION OF TITANIUM DIOXIDE PIGMENTS IN A RENEWABLY-RESOURCED POLYMER
S. J. Granger , P. M. Niedenzu , A. H. Reid Jr. , W.T. Sedar Jr., May 2010
A primary attribute of pigmentary titanium dioxide is its ability to ensure opacity while providing a white background in a variety of plastic matrices. The mixing behavior of titanium dioxide at high solids loadings in a renewably resourced polymer was evaluated via compounding processing data and viscosity performance at various temperatures. The study involved the determination of the viscosity behavior of several different surface treated titania pigments when compounded in a polytrimethylene terephthalate resin containing 37% renewably sourced material, by weight, derived from corn.


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