CYCLE TIME REDUCTION IN MULTI CAVITY THERMOPLASTIC INJECTION MOULDS WITH NANO FLUIDS
In injection moulding, cooling phase generally takes major portion of the cycle time. Any reduction in the cooling time leads to increase in productivity. This is generally achieved by either enhancing the heat transfer rate or by decreasing the cooling water inlet temperature. In case of ambient with high atmospheric temperature and humid climate, decrease of coolant inlet temperature causes moisture condensation over moulds leading to reduction in mould life due to corrosion. Current research points towards the advantages of using a new class of fluids called Nano fluids as coolants which exhibit better thermal conductivity at normal operating temperatures to reduce cooing time in injection moulding of a sketch pen barrel. AL2O3 and CuO Nano fluids in varying concentrations of 0.02% to 0.1% in the base fluid 10% ethylene glycol and 90% water are used as coolants to achieve heat transfer enhancement. The experiments are conducted at different inlet temperatures and at different flow rates. The results indicated increased heat transfer coefficients and reduced cycle time when both the Nano fluids were used as coolants. This increase was achieved even at 30°C, 35°C and 40°C coolant inlet temperature which effectively eliminates the moisture condensation on mould. At 25°C coolant inlet temperature with CuO Nano fluid, a maximum heat transfer enhancement of 16% and for AL2O3 Nano fluid, a maximum heat transfer enhancement of 3% is obtained. Under these conditions, the maximum cycle time reduction of 2 sec and 0.4 sec is achieved for CuO and AL2O3 Nano fluids respectively.