Critical thickness estimation in ISO-MC cards injection using CAE tools

Injection moulding is a widely used polymer processing operation because of its ability to produce net-shaped components of good dimensional accuracy with a relatively short cycle time. Nevertheless, only few industries use CAE tools to optimise the injection process or to design the mould. Today, many industries have more confidence in their know-how than in the prediction on a commercial simulation software package. In this work we use C-MOLD to estimate the critical thickness for injection by studying the flow parameters in the thinnest section point of the ISO-MC card. We simulated the process with the geometry of a microchip credit card, which has a minimum thickness of 250 μm (memory microchip area thickness), and studied the variation of different process parameters as this thickness increased. The maximum thickness was fixed at 800 μm (global thickness) and the minimum thickness was modified from 250 to 500 μm. Different injection points and filling times were used to optimise the process. The pressure and temperature variations during the filling process are the most sensitive parameter. The plot of these parameters versus the minimum thickness allowed us to estimate the critical thickness of 360–390 μm for this geometry using different ABS plastics formulations. The plots show how the magnitudes are stabilised in a plateau when the thickness is higher than 390 μm but they increase as the thickness decreases below 360 μm.