Experimental verification of an optimal thermal design in a compression mold

Abstract A production sheet molding compound (SMC) mold for an automotive hood outer panel was instrumented with 64 thermocouples to measure cavity surface temperatures along two cross‐sections in each mold half and regulate the supply of steam to each heating line. The positions and temperatures of each heating line in the mold were optimized using an in‐house computer program to produce a minimum spatial variation in cavity surface temperature during steady cyclic molding. Provision was also made to heat the mold conventionally so that optimal and conventional heating could be directly compared in the same mold. While maintaining a 78 s overall molding cycle, the conventional heating system eventually produced a 10°C temperature variation on the cavity surface. This, in turn, led to serious resin undercure and severe difficulties in removing the part from the mold. When the optimal heating design was substituted in place of the conventional system, the surface temperature variation was reduced to less than 3°C and the problems experienced with conventional heating disappeared. For the most part, the measured temperatures in these experiments agreed with the results of the computer analysis to within 1°C.