Study of surface finish of fiber-reinforced composite molds

One of the primary processes for the production of composite parts is the liquid composite molding process. This process is based on the injection of resin into a mold, which is usually metallic. Today, studies are being undertaken to produce these molds using Hextool (TM), a carbon fiber-reinforced thermosetting plastic. The molds, constructed by draping prepregs, must be finished by free-form machining to ensure the dimensional and surface quality requirements. An arithmetic roughness of 0.8 mu m is required, and this quality is not attained by milling operations. Thus, a manual polishing operation is necessary. However, to minimize the time taken by this manual operation, it is necessary to verify the roughness obtained by milling. Thus, the work presented in this article consists first of a study of the capability of milling to produce molds from Hextool with given surface quality requirements. The conclusion of this study is to define values of radial depth of cut to attain a surface quality with minimum machining time. Second, this work highlights how to replace the manual polishing operation by a machining operation with an abrasive diamond tool. Thus, the capability of an abrasive diamond tool to machine a mold with high surface requirements is discussed.