Enhancing Plasticizing Rate of The Injection Moulding Machine Screw With Polyflow Modelling & Simulation

Abstract

Injection moulding has been an ever evolving technology in field of plastic components manufacturing. For many years, there have been several attempts to improve the performance of the injection moulding machine. But there still remains the scope of analysing the polymer behaviour inside the screw-barrel system by means of numerical simulation. With recent developments in computational fluid dynamic tools, this task has become an active area of experiments. This work of thesis proposes a noble design of the reciprocating screw and aims to improve the rate of plasticization of the injection moulding machine. The flow behaviour of the polystyrene material is also observed along the screw profile. The commercial software used for modelling the screw model is Creo Parametric and ANSYS Polyflow for carrying out the numerical simulation. At first, a benchmarking problem is identified and numerically simulated to validate software suitability for such kind of problems. An existing standard screw is considered for numerical simulation to verify the results with the experimental observations in terms of pressure difference during re-fill operation. A novel design for reciprocating screw is proposed. This design is able to significantly improve the pressure difference throughout the profile and melt quality, making it possible to achieve a higher rate of plasticization. The Power Law model for shear rate dependency on viscosity is used to predict the flow behaviour of the material. Applying the rheological and material properties of polystyrene, the pressure difference and velocity are predicted. The results obtained shows a significant improvement in the pressure distribution from 18.34MPa in basic screw to 41.27MPa in proposed screw. Also, the velocity tends to increase in the metering section from 402.20 mm/s to 611.30 mm/s, leading to an improved plasticizing rate.