Messung von pvT-Daten bei prozessnahen Abkühlraten und deren Einfluss auf die Simulation von Schwindung und Verzug mit Moldflow Plastics Insight

Translated title of the contribution: Measurement of pvT data at process near cooling rates and its influence on the simulation of shrinkage and warpage with Moldflow Plastics Insight

Research output: ThesisDoctoral Thesis

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Abstract

In this thesis the topic was picked up that the simulation of shrinkage and warpage of injection moulded thermoplastic parts does not provide the desired reliability yet. From this the motivation was derived to improve the simulation results with Moldflow Plastics InsightTM (MPI) by using a new measurement method for the determination of pvT-data. A new measuring apparatus and special evaluation method for the measurement of pvT-data at process near cooling rates (hcr-pvT for high cooling rate pvT) were developed and the obtained measuring results were compared to standard measurements. Two amorphous and two semi-crystalline materials were investigated. The achieved cooling rates of approx. 15 K/s are about two orders of magnitude higher than in standard measurement methods. The hcr-pvT data of the amorphous thermoplastics were shifted to higher values in the temperature region below glass transition temperature compared to the standard data. For the semi-crystalline materials the difference to standard data was even more pronounced. The materials showed almost amorphous character regarding the shape of the curves and the transition between melt and solid state was strongly shifted to lower temperatures in comparison to standard measurements. The level of the specific volume of the hcr-pvT-data in the solid state is also clearly higher compared to standard data. With the four selected materials various box shaped test parts with different wall thickness variations were moulded. Afterwards, these parts were digitized using an optical 3D-scanner. The boxes were modelled as 3D- and Fusion-models in MPI and simulated using the process settings of the experiments. For the evaluation of the shrinkage and warpage prediction some representative dimensions of the boxes were defined. The simulated deformations of those dimensions were compared to the real measured part dimensions. The calculations were performed with standard pvT data and hcr-pvT data, respectively, in order to show the potential of improvement. For the investigated amorphous polymers an improvement of the accuracy of the predicted shrinkage and warpage could be achieved, whereas for the semi-crystalline thermoplastics some improvements stand directly opposed to many poor results. An explanation for this finding could be seen in the fact that the crystallization process does not only depend on the cooling rate but also on the imposed shear deformation (shear induced crystallization), which can neither be taken into account with standard methods nor this hcr-pvT apparatus.
Translated title of the contributionMeasurement of pvT data at process near cooling rates and its influence on the simulation of shrinkage and warpage with Moldflow Plastics Insight
Original languageGerman
QualificationDr.mont.
Supervisors/Advisors
  • Langecker, Günter R., Assessor A (internal)
  • Brand, Clemens, Assessor B (internal)
Publication statusPublished - 2009

Bibliographical note

no embargo

Keywords

  • pvT-data
  • simulation
  • shrinkage
  • warpage
  • injection moulding

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