Computational Technology Resources - CSETS

Keywords: gas assisted injection moulding, live feed mouldin, profile extrusion die design, optimisation, robust design, fluid-structure interaction.

In the first section, finite element techniques for the 3-dimensional simulation of some advanced injection moulding technologies for plastics are outlined, and applied to examples of gas assisted injection moulding and live feed injection moulding. Figure 1 shows a typical result for the simulation of the filling, the primary and the secondary gas penetration for a car door handle.

**Figure 1:** Initial plastic position before primary gas penetration (left), and gas injection including blowout during gas injection.

The second section introduces the simulation of uPVC profiles after leaving the profile die. This includes the heat transfer calculation and the determination of warpage. Figure 2 shows the results of the cooling simulations of a uPVC profile.

**Figure 2:** Temperature profiles and air flow pattern inside profile cavities due to cooling for a profile at various stages of cooling [1].

In the third section, deterministic optimisation is applied to the design of profile extrusion dies. Figure 3 shows the optimised cross-section of the profile die for the manufacture of a uPVC window profile.

**Figure 3:** Optimisation results depicting departure of flow rate in each partition from the target value in %. Initial design (in brackets) compared with final values [3].

In the final section, robust design techniques are applied to the design of slit dies for the manufacture of thin sheet materials. The coupled simulation solving the fluid-structure interaction problem takes the die deformation into account. Figure 4 shows the exit flow rate distribution for two cases of a choker bar profile optimisation.

**Figure 4:** Worst, best and nominal exit flow-rates for several solutions on the 100-sample `Pareto' curve.

1: I. Szarvasy, "Automatic CAD Model Based Simulation of PVC Extrusion and Calibration", PhD thesis, School of Engineering, University of Wales Swansea, January 2005.
2: H.J. Ettinger, "Computer Aided Simulation and Design of uPVC Profile Extrusion Dies", PhD thesis, School of Engineering, University of Wales Swansea, August 2004.
3: S.J. Bates, "Development of Robust Simulation, Design and Optimisation Techniques for Engineering Applications", PhD Thesis, University of Wales Swansea, 2003

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