**2. Production techniques in AEC**

The historical evolution of architecture is closely linked to that of construction techniques. The combination of available techniques and workforce—in quantity and quality—has driven the sector since antiquity, and architects had to know and carefully consider them as a premise of their design. Moreover, while some techniques have emerged from within the field of architecture, in the effort of solving construction problems, very often it was the spillover of advancements in other fields of science and technology that determined the adoption of new production techniques in architecture.

are different from one another, i.e., customized elements. It is the 'mass-customization' paradigm. The use of CAD/CAM software became the key tool in the hands of designers and architects to harvest this new production potential. In fact, the 'virtual' design within the software could be now transformed into something tangible driving the production machines directly from the computer and without the need for any 'translator' or skilled human intermediary. As in the First Industrial Revolution, workforce manual skills were not relevant anymore, but unlike under the previous paradigm, it was now not necessary or advantageous to reduce the complexity of the design elements and to embrace radical simplification. As we will see dealing with 3D printing techniques, it is worth noticing that this new approach started off as a convenient tool for fast prototyping, but due to technical advancements, it is potentially becoming a method for the production of final parts or even entire architectures, as it has already become

The Evolution of 3D Printing in AEC: From Experimental to Consolidated Techniques

http://dx.doi.org/10.5772/intechopen.79668

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a production technique in some fields of advanced engineering, such as aeronautics.

Additive manufacturing (AM) is possibly the most disruptive production paradigm stemming from the adoption of CNC machines. It promises to transform a(ny) virtual shape designed in a software environment to a real-world object, as much as 2D printing is transforming virtual pixels into ink dots on a sheet. It requires that the object to be printed be 'rasterized' into discrete elements, which usually is performed through the use of Mesh geometries in the CAD environment. More often than not, additive manufacturing techniques are actually working by layered 'slices' (sections) of the desired object, so that the final shape results from the combination of subsequent, 2D designed, layers of material with a standard thickness.

1980–1981: Hideo Kodama (Nagoya Municipal Industrial Research Institute) invented and described two first additive manufacturing techniques based on photo-hardening of plastic polymers. This seminal work can be considered the ancestor of both photopolymerization and stereolithography. An application for patent was filed, but the inventor did not follow up

1984: Jean-Claude André (CNRS), Alain le Méhauté (CGE/Alcatel) and Olivier de Witte (Cilas) filed an application for patent of stereolithography, i.e., an additive manufacturing method whereby a laser beam selectively hardens a UV-sensitive liquid resin, following a sequence of cross-sections of the object to be printed. The patent filing was abandoned, and Chuck Hull filed a patent, granted in 1986. The system was based on ultraviolet laser light beams hardening crosssection by cross-section a resin contained in a vat. The .stl file extension Hull adopted is still in use today for most AM. He also founded 3D Systems, a company manufacturing 3D printers. 1987: Carl R. Deckard invented at UT-Austin the selective laser sintering technique, based on high-power (usually pulsed) laser beam that selectively fuses powder particles along crosssections of the desired shape. The powder can consist in plastic, metal, ceramic or glass, and is usually pre-heated in the bed just below the fusion point. A patent for a similar technique

**3. 3D printing history related to construction methods**

within the required one-year deadline after application [1, 2].

was filed in 1979 by R. F. Housholder, but it was not commercialized.

**3.1. History and evolution**

While such combination of workforce skills and production techniques has been consistent throughout the centuries, there have been some radical paradigm changes in their combination. In particular, while a sort of batch production of some architectural elements was present since antiquity, as well as in gothic architecture—as for bricks, tiles, and column drums—starting with the industrial revolution, such production in series acquired a more industrial character, and the relevance of skilled labor started to decline, while mechanized processes took off as the most decisive factor in production costs and quality. Modularity, which previously was rather an ideal set of geometrical relationships and proportions related to orders, started to become a necessary way of streamlining the production in series of identical base components, the only way industrialization could lower production costs as well as assembly times and efforts. Architectural practices and theories had to reflect these needs, and especially with the Modern movement, the trend toward simplification and use of standardized elements became common practice. The case of 'The Eames House, Case Study House 8' by Charles and Ray is a paradigmatic example thereof: the building was even designed and assembled starting from 'off-the-shelf' standard pieces, while trying to create an individual architectural character. Production in this case was a given before the design, and not the result thereof. Fast forwarding in history, the use of building information modeling (BIM) software has connected this trend to the realm of the design in the virtual (software) environment, especially as it allows and even encourages the use of available and industrially pre-fabricated architectural elements, such as doors and windows, and also rebars, trusses, and the like.

On the other hand, starting from the 1960s, the degree of geometric freedom and control over the produced elements started to increase through the use of computer-aided design (CAD) and computer-aided manufacturing (CAM) software, even though the constraints of a required standardization of elements continued to be present for a cost-effective production. Through Bézier curves and Non-Uniform Rational B-Spline (NURBS) modelers, it was now possible to create more organic and complex shapes. An early example thereof was the Renault 'Unisurf' software used to design and produce car parts. However, the process often required non–computer-controlled phases and the mass-production of standardized pieces.

It was in the last 10–20 years that a more streamlined and integrated use of computer numerical controlled (CNC) machines started to allow for a new change in paradigm within the architectural field. While a few centuries ago, the spillover of industrialization techniques meant that standardization and simplification had to become the design approach to architectural projects because industrial production required identical elements to be mass-produced in order to lower the cost per unit, now it became possible to cost-effectively mass-produce elements that are different from one another, i.e., customized elements. It is the 'mass-customization' paradigm. The use of CAD/CAM software became the key tool in the hands of designers and architects to harvest this new production potential. In fact, the 'virtual' design within the software could be now transformed into something tangible driving the production machines directly from the computer and without the need for any 'translator' or skilled human intermediary. As in the First Industrial Revolution, workforce manual skills were not relevant anymore, but unlike under the previous paradigm, it was now not necessary or advantageous to reduce the complexity of the design elements and to embrace radical simplification. As we will see dealing with 3D printing techniques, it is worth noticing that this new approach started off as a convenient tool for fast prototyping, but due to technical advancements, it is potentially becoming a method for the production of final parts or even entire architectures, as it has already become a production technique in some fields of advanced engineering, such as aeronautics.
