Page 2 - Open-Access-Aug-2020

point of view

industrial robots from ABB, Kuka or other major players active D. contour crafting: published in 1996 by Prof. Berok
in this domain. then hoses and pipes are attached to the robots Khoshnevis, the concept of Contour Crafting aims at
and customized programming is done for these ends. Printed manufacturing of close to turnkey houses through a
materials are typically special mortars with no aggregates but combination of 3D construction printing and automation. While
chemical additives. Limitations of respective applications can the concrete shell is printed bottom up, all other building
be derived from sizes and dimensions of employed industrial components like rebar, piping, wiring, electrical installations,
robots, nature and cost of materials and respective product tiles, floors, etc. except for doors and windows are automatically
offerings. It is likely that some of these products will find their inserted or installed as the whole structure rises. Contour
respective markets or niches to make a sustainable business out Crafting Corporation, headquartered in Los Angeles, headed by
of it. CEO Berok Khoshnevis, realizes the concept of Contour Crafting
via two development steps: the first generation fully covers the
B. 3d shell component Printing: respective applications first robotic function which is printing concrete house shells of
aim at building house shells by printing many individual and up to 200 [m ] floorplan in one shot. The second generation will
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hollow wall objects, either on-site or off-site, stack or assemble provide the full set of robotic functions. The first generation has
them and then fill them up with poured concrete and finally been introduced at Bauma 2019 in Munich. The dynamically
finish the shell structure (also refer to chapter 3. Materials). exhibited CC-108 proprietary gantry printer is light; the whole
Here again, in most cases industrial robots come into play, and, robot including delivery system weighs less than 1,000 [kg], and
again special mortars serve as printed materials. intentionally is easily positioned or repositioned by only two persons. in terms
or unintentionally, this approach mimics the globally existing of iP, the company holds over 100 national and international
production of concrete precast panels. the difference, however,
is that precast panels are solid functional walls already when patents and has won two prestigious nASA awards.
they arrive at the jobsite. they consist of standard concrete and
contain all required rebar, pipes and electrical pre-installations 3. materIals
whereas their mortar printed counterparts lack all of this. Based For 3D construction printing applications aiming at printing load
on the available evidence, this approach cannot compete bearing structures (buildings), one first key matter is materials.
with well-established pre-fabrication facilities in terms of cost, the printed materials, to be precise. in the internet, 3D
time, and quality of produced components. in addition, it has construction printing seems to be synonymous with concrete 3D
to be clearly stated that these concepts only focus on house printing. Almost everyone on the net claims to print concrete.
shells, which typically account for only 25 to 35% of the total
construction cost of a building. Why? Because everybody, including authorities, knows and trusts
concrete. Concrete is everywhere. it is a technically proven,
C. 3d shell Printing: this approach aims at manufacturing lasting, globally available and relatively inexpensive material.
house shells, rather than complete houses. respective these three factors matter a lot in a high volume business like
applications aim at printing house shells directly at the jobsite. construction. However, in most cases, the reality is that printed
Some intend to print the shell in one shot, so no repositioning materials are rather expensive toothpaste-like cementitious
of the printer is required. Some need repositioning of the materials and not standard concretes. Special mixtures with
printer in order to complete the printed shell structure. in other either no aggregates or aggregates smaller than 4 mm in grain
words, in this approach complete shell structures are printed, size. Why is this important? Four reasons: first, there is the
unlike the previous approach (B) in which only segments of the price component as already mentioned above. A high volume
shell are printed. Companies that have adopted this approach business like construction cannot afford using materials that are
either develop and use customized equipment, or they rely on more expensive as a substitute for an inexpensive and proven
a configuration of the off-the-shelf OEM products, which have material. Second, the effect of adding gravel makes it possible
been originally designed for other applications. to determine to reduce the cement content, which improves dimensional
competitiveness, further key questions are: stability of the printed material and all this reduces the risk of
shrinkage cracking. if there are no aggregates, there is no such
- What material is printed?
effect. third, these special mixtures have different material and
- How quickly and easily can a printer be positioned or re- elastic properties than standard concretes. As in many cases,
positioned by operators? the printed wall parts are intended to serve as lost formwork,

- What is the system weight, handling time and effort? the wall cores are then filled up with standard concretes.
Due to the significantly different material properties, these
- How much personnel is required?
two materials do not form a monolithic structure and hence
- What is the time, cost and quality relation vs. local the structural performance of the final structure is affected.
competition? therefore, the printed special mixture structures are typically

76 The IndIan ConCreTe Journal | augusT 2020