Opvarmeligt værktøj

The tool incorporates an electrically conductive ceramic part (16) which heats a tool member at least in the area of a surface (18) which contacts the molten material. The ceramic part is integrated in or with the tool member (12,14). The tool incorporates an electrically conductive ceramic part (16) which heats a tool member at least in the area of a surface (18) which contacts the molten material. The ceramic part is integrated in or with the tool member (12,14). A controlled low voltage with high current is passed through the ceramic part (16) to achieve a high heat output in the latter. The ceramic may be sandwiched in the tool member (12,14) so that it lies close to or immediately below a melt contacting surface (18). Connection between the ceramic part and another part of the tool, e.g. a housing part or supporting part, is preferably by diffusion welding. The ceramic part may alternatively have a surface which contacts the melt and forms a cavity surface or a hot runner channel. For the latter a ceramic with high abrasion resistance is employed. The ceramic surface may be shaped to match the forming cavity profile. When cooling channels are required in the ceramic they are produced by erosion. The ceramic part may be mounted on a tool steel member (14) which acts as a carrier. Specific areas of the ceramic part surface may be electrically isolated. Current may be supplied by mounting the ceramic part on an electrically conducting surface.