A method and a system for forming a polymeric resin mold for molding plastic items, wherein the method includes: (a) using a rapid-prototyping process to create a polymeric resin shell having a configuration in the form of the mold; (b) introducing a reinforcing material into the shell; and (c) curing the shell. The system includes a rapid-prototyping apparatus that creates a plurality of the polymeric resin shells on a platform; a reinforcing material introduction apparatus that introduces a reinforcing material into each of the shells while the shells are on the platform to form a plurality of uncured molds on the platform; and a curing apparatus that cures the shells while they are on the platform.