ساخت و تولید افزایشی در بخش مبلمان چوبی: پایداری تکنولوژی، مزایا و محدودیت های انطباق Additive manufacturing in the wood-furniture sector Sustainability of the technology, benefits and limitations of adoption

1. Introduction Currently the world economy is going through a period of transition and change in the manufacturing landscape. Jeremy Rifkin believes that the phase of digitization, the third, has just begun and has yet to fully show all its implications and its potential (Rifkin, 2011). On the contrary Klaus Schwab, a German Engineer and Economist, best known as the Founder and Executive Chairman of the World Economic Forum, argues in his book The Fourth Industrial Revolution, that the first three revolutions are the transport and mechanical production revolution of the late eighteenth century; the mass production revolution of the late nineteenth century, and the computer revolution of the 1960s. He agrees that some people might consider the fourth revolution just an extension of the third but claims that the scale, speed and impact of the latest technologies deserve a revolution of their own (Schwab, 2016). Whether the revolution in act today is the Third or the Fourth, it can be said that one of the most significant drivers of this change is the emergence of advanced manufacturing technologies that are enabling more cost- and resource-efficient small-scale production. In combination with other prominent trends such as servitisation (Neely, 2008), personalization (Zhou et al., 2015) and prosumption (Fox and Li, 2012), the emergence of Additive Manufacturing (AM), commonly known as 3D printing, as a direct manufacturing process, is leading companies to rethink where and how they conduct their manufacturing activities (Ford and Despeisse, 2016). AM is defined as “the process of joining materials to make objects from 3D model data, usually layer upon layer, as opposed to subtractive manufacturing methodologies, such as traditional machining” (ASTM, 2010). The 3D printing process works as follows. Once the user has selected an electronic design blueprint and loaded up the raw materials into the 3D printer, the machine begins its work. In a process that can take several hours to days, the 3D print head deposits layer upon layer of tiny droplets of raw material to form the object. Depending on the complexity of the design, the machine is able to switch between different print heads to work with multiple materials and form shapes with a number of colors and diverse textures. Eventually, after countless back-and-forth sweeps, a three-dimensional object forms out of the raw material (Lipson and Kurman, 2010). This technology evolved during the mid-1980s when computing and control systems progressed (Hopkinson et al., 2006); in its early years AM was mostly applied for the fabrication of conceptual and functional prototypes, which is also known as rapid prototyping (Mellor et al., 2014). Only recently 3D printing has gained much attention, as the process has proven to be compatible with industrial manufacturing beyond prototyping (Berman, 2012; Gershenfeld, 2012; Reeves, 2008). Therefore the concept of rapid manufacturing (RM), a production of end-use parts from AM systems (Hague et al., 2004), emerged in the last decade; though its economic impact has remained modest (Levy et al., 2003). Bai et al. (2017), employed a patent bibliometric analysis and found that at the moment the USA, Japan, and Germany are the leading countries in 3D printing technology, although the technology accumulation patterns of these countries are rather different. Additionally Israel and Italy also have good performance in the fast-growing technology sub-fields. The most commonly applied processes are Stereolithography (SLA), selective laser sintering (SLS), digital light processing, fused deposition modeling, selective laser melting and electron beam melting (Petrovic et al., 2011). Although the technologies have many similarities as their development was simultaneous there are also distinct differences between each one (Kulkarni et al., 2000). Reviews of the numerous AM technologies have been performed in previous works (Gibson, 2010; Groover, 2007; Hopkinson et al., 2006). Polymers, alloys of aluminum, steel and titanium, as well as ceramic composites are currently printable at a minimum layer thicknesses of 20-100 μm, depending on the process and the physical state of the material (Hopkinson et al., 2006). Therefore, 3D printing can be applied to various manufacturing markets. The decision to invest in additive manufacturing technologies must be linked to the market and product characteristics. Generally, the product characteristics are: products with a degree of customization; products with increased functionality through design optimization and those of low volume (Mellor et al., 2014).