Читать книгу Rethinking Prototyping - Группа авторов - Страница 135

Due to the rise of complex free-form shapes in architecture the glass industry had to develop new strategies and adapt their production lines. Now we differentiate between two main bending methods, the Annealed Glass Bending and the Tempered Glass Bending. These two techniques differ in the type of glass used, bending tools or machines and application of the fabricated elements. Based on many associated parameters of the glass, like edge curvature or panel geometry (Fig. 3) the costs for producing cylindrical and conical glass is quite the same, but costs for double curved glass are much more higher.

For double curved panels one needs to build a mould for every shape. (Eigensatz et al 2010) propose a method for computing different types of curved panels for given panel edges. Their algorithm depends on the choice of a coordinate system in the panel’s centre, which in turn determines the direction of curvature lines and thus reflection properties. Furthermore, the panel’s edge curves have to be given.

Fig. 3 Special glass panel types: a) cylindrical, b) cylindrical, edges not aligned, c) paraboloid, d) toroidal, e) double curved, three edges aligned, f) conical, g) anticlastic, h) synclastic. Panel types a, b c, f are developable, and therefore ruled surfaces, panels d, e, g and h are double curved surfaces.

There are a few advantages of conical glass elements over double curved elements. They are more cost efficiency and easier installation. This depends primarily on the geometry of the edges and further the sealing of the joints of watertight structures.

Cylindrical panels and elements of annealed glass that are based on ruled surfaces can be produced with the same technique (Fig. 1).

Fig. 4 Annealed Glass Bending with gravity force method is set up as depicted left and produces ruled surfaces, of which the types on the right are special cases: rotational cylindrical, rotational conical, general cylindrical and general conical (from top left to bottom right).