Faster cycle times mean improved productivity and profitability in plastics processing. Constant efforts are being made to reduce and optimize cycle times. Thinner wall parts with wall thicknesses of 1mm and less are becoming more common. Extensive research has been done in developing thinner parts. However, there is always a limit on how thin one can go. Cooling time takes up the major portion of the cycle and it is a function of many processing variables, viz. mold and melt temperature being the most important ones. The heat transfer mechanism during cooling also depends on the thermal conductivity of the core/cavity material. This thesis compares two different mold construction materials with different thermal conductivities.; The part selected was a plunger which goes into the assembly of a pen and whose function is to snap into a specified position when pressed. The parts were molded with DuPont Delrin{dollar}spcircler{dollar} at different processing conditions. These parts were tested to measure the overall height dimension which was used as a controlling parameter (part quality). 420 stainless steel and Moldmax{dollar}spcircler{dollar} LH (beryllium-copper alloy) were used as core pin materials. The mold was run under similar processing conditions and then optimized to get the required part quality. It was found that using the Be-Cu alloy reduced the cycle time (cooling time) by 20%. Core pyrometer readings showed that the heat dissipation of the Be-Cu alloy material was much higher than that of the stainless steel.
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