3D scanning & 3D printing techniques for historical buildings
Techniques for 3D scanning and 3D printing for refurbishing façades of historic buildings with rich details
Different technologies of three-dimensional acquisition and rapid prototyping can be applied in conservations procedures and restoration of architectural facades of historic buildings, depending on the required accuracy and the characteristics of the object to be surveyed and reproduced as a solid model. Usually, digital survey procedures and 3D printing are applied: for the integration of missing parts of decorative elements; to use the solid models for museum exhibition; to replace original decorations located outside (exposed to weather conditions) for conservative reasons; or for restoration and refurbishment procedures.
It is possible to three-dimensionally survey a simple object/surface even by using a common photographic camera and a 3D photogrammetry software; textures data are acquired as well. The process is similar to the one described above but it’s not necessary the registration phase, which is accomplished by the photogrammetric software before generate the 3D point cloud.
Three-dimensional models obtained by using these technologies must be processed and prepared for 3D printing. Point clouds must be triangulated to build a 3D mesh. Possible holes or polygons intersections have to be narrowly checked, and the "thickness" of the prototype has to be defined, thus generating a compliant STL files. The application of a three dimensional "texture" to the model in order to "differentiate" the copy from the original can be accomplished at this stage.
Prototyping or 3D printing techniques to be preferably used are based on deposit of material (layers), usually the FDM (Fused Deposition Modelling) or CNC (computer numerical control). For parts of small size and low mechanical strength can be used economical plastics materials such as ABS or PLA or the most expensive and resistant Nylon. Within the “slicing” procedures, layers are printed from the base to the top in order to obtain the complete solid model, that can be injected with an acrylic resin. The material which the solid models are made of, allows experimentations concerning the colouring of the surfaces according to restoration theories and techniques.