Development of metal filled epoxy inserts for injection moulding process

In this study, aluminium filled epoxy (EA) mixed with brass (EAB) and copper fillers (EAC) were fabricated into moulding inserts for producing mechanical testing specimens of plastic material through injection moulding process. The moulding inserts consisted of cavity and core blocks which are CNC machined into specific dimensions of the tensile strength and Izod test specimens based on ASTM standards. Epoxy inserts were assembled into the mould base as fixed and moving halves which were mounted on the plastic injection moulding machine. Polypropylene was used as the specimen material and the simulated processing parameters from plastics flow analysis were obtained at 177 bar of injection pressure, melting temperature of 240.1°C and holding pressure of 149.6 bar. However the actual settings were different from simulation whereby, the injection pressure was higher by 41% and temperature was reduced by 10%. Injection speed was set at 50 mm/s and the total cycle time was between 48s to 63.54s. After demoulding, mechanical tests were conducted, in order to investigate the behaviour of specimens obtained from all inserts as compared to specimens produced from conventional metal moulds. Results indicated that EA moulded part produced higher yield tensile strength of 36.3 MPa and impact energy of 1.823J, compared to conventional metal moulded parts of 33.8 MPa and 0.002J. EAB and EAC inserts indicated high tensile modulus at 1640 – 1670 MPa and their moulded parts showed similar result for impact energy and strength with EA. This result confirmed that mould materials have different effect on the mechanical properties of the injected parts.