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Evaluation of a Model Describing the Advancing Flow Front in Injection Moulding

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Published/Copyright: June 5, 2013
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International Polymer Processing
From the journal International Polymer Processing Volume 17 Issue 2

Abstract

The simulation of the advancing flow front during mould filling in the injection moulding cycle is important as a way of anticipating manufacturing defects, particularly different types of welds, air traps, cold spots and hot spots. The purpose of the present work was to evaluate a model (the distance model) simulating the advancing flow front and predicting potential issues related to the progression of the flow front such as welds and air traps. The distance model is based on a mathematical theory of Hele-Shaw flow for strongly shear-thinning fluids, i. e. fluids with a power-law index, n, equal to 0,3 or preferably less. Two grades of general-purpose polystyrene were selected according to their abilities to shear thin (weakly or moderately strong) at the selected processing temperature and in the typical shear rate range of the injection moulding process. The two grades were injection moulded into twelve mould configurations derived from two similar single-gated moulds. The flow length from the gate to the weld was measured in the mouldings obtained at three distinct rates of filling (conventional, slower and faster) and compared to the flow lengths obtained by the distance model. Good agreement was found between the predicted flow lengths and the experimental flow lengths at the conventional and faster filling conditions. Larger deviations between simulation and experiment were found at the slower filling rate, particularly for the weakly shear-thinning polystyrene grade. Some comparisons were also made with the predictions obtained using the commercial simulation code Moldflow. A comparison between the advancing front predictions of the distance model and experimental short shots of a commercial polypropylene grade in a lure-box type of mould geometry showed that the distance model, despite its simplicity, could probably be used to detect welds and air traps in more complex and practice-related mouldings.

* Mail address: A. Boldizar, Dept. of Material Science and Engineering, Chalmers University of Technology, SE-41296 Göteborg, Sweden
Received: 2002-2-1
Accepted: 2002-2-14
Published Online: 2013-06-05
Published in Print: 2002-05-01

© 2002, Carl Hanser Verlag, Munich

Articles in the same Issue

  1. Editorial
  2. Thirteenth of a Series: The First and Best Industrial Polymer Rheologist — Melvin Mooney (1893–1968)
  3. Single Extrusion
  4. A New Method for Simulating the Conveying of Solid Pellets
  5. A 3D Numerical Study of Fluid Flow and Heat Transfer in a Single Screw Extruder
  6. Pressure/Throughput Behavior of a Single-screw Plasticising Unit in Consideration of Wall Slippage
  7. Computational Study of the Velocity Field in the Conveying Element of a Ko-kneader with CFD Method
  8. Reactive Extrusion
  9. Modification of Polyolefin with Maleic Anhydride/Styrene and Methyl Methacrylate/Styrene
  10. Fibers and Films
  11. Direct Measurement of Fiber Temperature in the Continuous Drawing Process of PET Fiber Heated by CO2 Laser Radiation
  12. Injection Molding
  13. Evaluation of a Model Describing the Advancing Flow Front in Injection Moulding
  14. Process Design for Reducing the Warpage in Thin-walled Injection Molding
  15. Composites
  16. Preferable Filament Diameter Ratios of Hybrid Yarn Components for Optimized Longfiber Reinforced Thermoplastics
  17. Squeeze Flow Rheology of Glass Mat Thermoplastic (GMT) in Large Tools and at High Closing Velocities
  18. Analysis of Heat Flu from Molten Polymers to Molds in Injection Molding Processes
https://doi.org/10.3139/217.1682

Articles in the same Issue

  1. Editorial
  2. Thirteenth of a Series: The First and Best Industrial Polymer Rheologist — Melvin Mooney (1893–1968)
  3. Single Extrusion
  4. A New Method for Simulating the Conveying of Solid Pellets
  5. A 3D Numerical Study of Fluid Flow and Heat Transfer in a Single Screw Extruder
  6. Pressure/Throughput Behavior of a Single-screw Plasticising Unit in Consideration of Wall Slippage
  7. Computational Study of the Velocity Field in the Conveying Element of a Ko-kneader with CFD Method
  8. Reactive Extrusion
  9. Modification of Polyolefin with Maleic Anhydride/Styrene and Methyl Methacrylate/Styrene
  10. Fibers and Films
  11. Direct Measurement of Fiber Temperature in the Continuous Drawing Process of PET Fiber Heated by CO2 Laser Radiation
  12. Injection Molding
  13. Evaluation of a Model Describing the Advancing Flow Front in Injection Moulding
  14. Process Design for Reducing the Warpage in Thin-walled Injection Molding
  15. Composites
  16. Preferable Filament Diameter Ratios of Hybrid Yarn Components for Optimized Longfiber Reinforced Thermoplastics
  17. Squeeze Flow Rheology of Glass Mat Thermoplastic (GMT) in Large Tools and at High Closing Velocities
  18. Analysis of Heat Flu from Molten Polymers to Molds in Injection Molding Processes
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