Practical guidelines far predicting steady state cure time during sheet molding compound (SMC) compression molding

The longest part of the molding cycle during SMC compression molding is the curing stage. Thus it is extremely important to be able to predict its dur ation to estimate the cost of manufacturing a new part, During an SMC moldi ng cycle, the mold surface temperature drops suddenly when it contacts the cold charge. The surface temperature then gradually recovers as heat is con ducted from the interior of the mold and the resin releases heat during cur ing. In general, this exchange of heat remains locally unbalanced, causing a gradual decrease in the local surface temperature. To avoid blistering, t he cure time must be Increased with consecutive moldings until a steady sta te value is achieved It,,,l. In this paper, we present a series of charts t hat can be used to estimate the stead?; state cure time for new parts. Thes e values can then be used to estimate the manufacturing cost.