A tool system for molding an article comprising a tool (100) having a tool surface (110) for forming an article, the tool surface (110) comprising a plurality of tool zones, a plurality of fluid flow paths (151, 152) to direct the flow of a heating or a cooling fluid to individual tool zones, heating means comprising an in-line heater (150) for heating fluid passing through a respective heating fluid flow path and cooling means comprising a cooling fluid flow path, the cooling fluid flow path bypassing the in-line heater of the heating fluid flow path.