Resin Transfer Molding

Resin Transfer Molding (RTM)

The RTM process was developed from cold cast molding in the 1950’s. It served the purpose of low cost production by utilizing metal molds while achieving glossier and smoother finishes than those made by hand lay-up or spray up processes. Recent development of RTM has adopted vacuum processes to eliminate voids and increase the liquidity of the resin which combined with low shrinkage resin material can form parts compatible to the quality of the SMC process. The raw materials used in RTM are resin, surface veil, continuous mat, pigment paste, filler, and curing agent. Recently, some prepreg materials are also used in replacing the continuous mat process. Aluminum casting molds are also replacing fiberglass molds for longer life. Molds that are made properly can be used to make more than ten thousand parts. The latest development is fast cure forming. It is targeted to make four parts per hour per mold. The RTM process is suitable for smaller production at a rate of 20,000 parts per year. It is a low investment cost production process.