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Department of Engineering, ICT and Technologies for Energy and Transport Patent Title Reproduction method. Ref. CNR 10278 Assignee(s): CNR CNR Institute: ISTI Main Inventor: Paolo Cignoni Countries: IT Priority date: 25/07/2013 Abstract Method to fabricate a cross-joined physical structures starting from a given digital 3D model (represented by a triangle mesh). These cross-joined structures are composed of several (hundred) unique interlocking planar pieces whose 2D profiles are automatically generated by the proposed method. These planar pieces are cut by a laser cut machine and manually assembled into a rigid self-supporting object whose shape approximates the input 3D model. These structures are composed by interlocking ribbon-like planar pieces that are approximately perpendicular to the surface and that, when available, follow a cross field defined over the surface of the 3D model. The proposed approach is based on three main contributions: Interlocking mechanism, Joinery abstractions through graphs and Generation and placement of the slices. Background Wooden Puzzles build by crossing slides are well known. Commercial examples are available and they constitute a significant market. However, all these models are laboriously designed by hand by skilled artists. Tailored CAD tool, like 123DMake, can help the design of simple interlocking structures based on the classic waffle slit scheme, but are unable to produce complex arrangements. Technology The proposed approach is based on three main contributions: “Interlocking mechanism”, “Joinery abstractions through graphs” and “Generation and placement of slices”. The Interlocking mechanism has been extended by relaxing the geometric constraints that seriously limit the quality of the reproduction. We have introduced a graph based mathematical representation of the arrangements and devised a slice placement strategy that follows a cross field for an higher fidelity in the representation. Advantages and Applications The present invention allows the fabrication of low cost illustrative representation of 3D objects. The shape of the pieces of structure are generated automatically and can be assembled to compose a self-supporting robust structure. With respect to the classical interlocking mechanism, this method is capable of more flexible joinery’s and allows a better adaptation to the characteristic shape of the initial 3D object. Development stage A prototype implementing the entire pipeline is already available; it is capable of generating a model that can be printed with laser cutting techniques. Together with the slices, it’s also provided a user guide useful for the assembly procedure. The technique has been experimented with several complex input shapes. 79