Effects of Process Parameters on the Skin/Core Distribution in Co-Injection: Experiments and Simulations Using a Simple Geometry

Abstract

In this work the effect of processing parameters on core breakthrough and material distribution during co-injection in a model mould has been studied. PMMA was used for the skin and ABS for the core. To identify the influences of the core volumetric fraction, its injection rate and temperature and the skin injection temperature a series of computer simulations and experimental tests were performed according to the design of experiments statistical approach. The results of statistical analysis performed on data coming from experiments and simulations are consistent, even if simulations overestimate the ABS content at which the breakthrough takes place.

Keywords:

• Breakthrough
• Co-Injection moulding
• Design of experiments

ACKNOWLEDGMENTS

The author wishes to thank Ing. Roberto Onori and Ing. Francesca Pavani for their collaboration in the planning and execution of the co-injection moulding experiments and is grateful to Teuco Guzzini S.p.A. for financial and operational support of this research.

Notes

CIR = Ram speed (mm/s)* −1 = 4; 0 = 6; +1 = 8.

CT = Core material injection temperature(°C) −1 = 220; 0 = 230; +1 = 240.

CC = Core material volumetric fraction (%) −1 = 30; 0 = 35; +1 = 40.

*Core material injection rate is set on the moulding machine as ram speed. As the cylinder diameter is 180 mm, the three ram speeds correspond to −1 = 100 cm³/s; 0 = 150 cm³/s; +1 = 200 cm³/s.

CIR = Core material injection rate (cm³/s) −1 = 120; 0 = 180; +1 = 240.

ST = Skin material injection temperature (°C) −1 = 220; 0 = 230; +1 = 240.

CT = Core material injection temperature (°C) −1 = 220; 0 = 230; +1 = 240.

CC = Core material volumetric fraction (%) −1 = 30; 0 = 35; +1 = 40.