Heightmap-based computing of the tool gap for additive manufacturing of paper embossing tools

Abstract

 Tools used for embossing paper and cardboard usually consist of two dies, which are inverses of each other. An important design parameter is represented by a defined gap between the fully closed dies. This is achieved by creating one of the two dies with an embossing relief that is displaced by a constant surface-normal offset. To facilitate fast data preparation for additive manufacturing of such embossing tools, a heightmap-based image data processing is developed, although the preparatory steps and resulting data may be also used for conventional manufacturing. The fundamentals of paper embossing tool layout and relief representation in heightmap images are explained and the developed process steps and their calculation bases are discussed. The focus is placed on the derivation of a heightmap with constant normal offset with respect to an input heightmap. For this purpose, image processing algorithms are elucidated to first determine the relief’s surface curvature and use this information to deduce the necessary alteration to receive a derived heightmap. The generated data is reviewed and evaluated regarding its suitability for the production of additively manufactured embossing tools, which is done by examining the data as well as the derived physical dies.