CNC milling is the most common form of CNC processes of subtractive fabrication that makes manufacturing of complex forms available. Alternatively CNC milling machines are operated with a set of commands and functions in alphanumeric format; that is using NURBS geometry as a tool for manufacturing parts of non-Euclidean shapes becomes possible and therefore the credibility of complex designs is out of question. Generally the most important advantage of CNC milling technology is the availability of producing complex parts with high detail. There are some drawbacks though, for example CNC milling is rather slow comparatively to other fabrication processes. "CNC milling has recently been applied in new ways in building industry - to produce the formwork (molds) for the off-site and on-site casting of concrete elements with double-curved geometry, as in one of the Gehry's office buildings in Dusseldorf" (Schnabel 2002). Additionally Frank Gehry used another CNC technology, laser cutting, for steel supports of masonry walls in Zollhoff Towers in Dusseldorf. Returning to examples of implementing of CNC milling one may name the production of laminated glass panels with complex curvilinear surfaces (Bernard Franken's BMW Pavilion, Gehry's Conde Nast Cafeteria).
Innovative CNC processing technologies (milling, cutting) along with the increasing interest in "new" materials is supported by the attention rising towards shell structures, which conflate the structure and the skin into one element thus creating self-supporting forms: "The idea of a structural skin not only implies a new material, but also geometries, such as curves and folds that would enable the continuous skin to act structurally, obviating an independent static system" (Giovannini 2000)
New materials, especially composites previously used in aero-space, automotive, shipbuilding industries etc. can be of particular interest to architects when constructing a light-weight structur