Walter Friesenbichler, Andreas Neunhäuserer, Michael Andreas Fasching, Evan Mitsoulis

    Research output: Non-textual formDigital or Visual ProductsResearch


    To establish closed-loop control of the injection molding process with regard to a self-optimizing process,
    quality models derived from injection molding simulations acc. to DoE are of crucial importance. Quality
    functions derived from simulation linking the process parameters with desired part quality (part weight,
    dimensions) allows running the production within the allowed process window realizing a robust injection
    molding process. It is well known that viscoelasticity of polymer melts [1,2] and pressure dependence of
    viscosity [3] play a major role in processing. Nevertheless these effects are commonly neglected in simulation
    of polymer melts resulting in remarkable deviations between the real pressure demand and the prediction via
    simulation. The effects increase strongly with raising pressure level for processing.
    The aim of this study was to compare measured data for the pressure demand in capillary rheometry as well
    as in injection molding with calculated values based on simulations. Particular emphasis had been given on
    viscoelasticity and the pressure-dependence of viscosity. The results from viscous calculations for different
    conical dies having different diameters, D, and length-to-diameter L/D ratios, were compared with those from
    viscoelastic modeling and viscoelastic modeling taking into account the pressure effect. Four injection molding
    nozzle geometries had been also used to reach apparent shear rates up to 800,000 s-1. Using oscillatory and
    capillary rheometry a full rheological characterization had been carried out for both a polypropylene-filled
    nanocomposite and a rubber compound (SBR).
    It was found that only the viscoelastic simulations were capable of reproducing the measured pressure drop
    very well [4], while any viscous modeling always strongly underestimates the pressures, especially at the higher
    apparent shear rates and L/D ratios. The experimental data have been fitted both with a viscous model (Cross)
    and a viscoelastic one (the Kaye - Bernstein, Kearsley, Zapas / Papanastasiou, Scriven, Macosko or KBKZ/
    PSM model).The data for pressure dependence of viscosity were measured on an injection molding
    machine rheometer with the help of a special rheological mold. Experimental data are evaluated taking into
    account the melt temperature rise due to dissipative heating.
    In addition the importance of pressure-dependence of viscosity for injection molding simulations of practical
    parts is shown for different thermoplastics (ABS, PS, isotactic PS) and a rubber compound (NBR) comparing
    measured pressures in the screw antechamber or the cavity with simulated pressure values. For pressures higher
    than 100 MPa the pressure-dependence of viscosity should be taken into account.
    Original languageEnglish
    Place of PublicationSlowenien
    Publication statusPublished - Apr 2017
    EventInternational Conference on Industrial Tools and Advance Processing Technologies - Grand Hotel Union, Ljubljana, Slovenia
    Duration: 24 Apr 201726 Apr 2017
    Conference number: 11

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