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The New Boundaries of 3D-Printed Clay Bricks Design: Printability of Complex Internal Geometries

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The New Boundaries of 3D-Printed Clay Bricks Design: Printability of Complex Internal Geometries

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The building construction sector is undergoing one of the most profound transformations towards the digital transition of production. In recent decades, the advent of a novel technology for the 3D printing of clay opened up new sustainable possibilities in construction. Some architectural applications of 3D-printed clay bricks with simple internal configurations are being developed around the world. On the other hand, the full potential of 3D-printed bricks for building production is still unknown. Scientific studies about the design and printability of 3D-printed bricks exploiting complex internal geometries are completely missing in the related literature. This paper explores the new boundaries of 3D-printed clay bricks realized with a sustainable extrusion-based 3D clay printing process by proposing a novel conception, design, and analysis. In particular, the proposed methodological approach includes: (i) conception and design; (ii) parametric modeling; (iii) simulation of printability; and (iv) prototyping. The new design and conception aim to fully exploit the potential of 3D printing to realize complex internal geometry in a 3D-printed brick. To this aim, the research investigates the printability of internal configuration generated by using geometries with well-known remarkable mechanical properties, such as periodic minimal surfaces. In conclusion, the results are validated by a wide prototyping campaign.
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Citation: Sangiorgio, V.; Parisi, F.;
Fieni, F.; Parisi, N. The New
Boundaries of 3D-Printed Clay Bricks
Design: Printability of Complex
Internal Geometries. Sustainability
2022,14, 598. https://doi.org/
10.3390/su14020598
Academic Editor:
Sayanthan Ramakrishnan
Received: 25 November 2021
Accepted: 2 January 2022
Published: 6 January 2022
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4.0/).
sustainability
Article
The New Boundaries of 3D-Printed Clay Bricks Design:
Printability of Complex Internal Geometries
Valentino Sangiorgio 1,2,3,4,* , Fabio Parisi 1,5, Francesco Fieni 6and Nicola Parisi 6
1ICITECH—Instituto de Ciencia y Tecnología del Hormigón, Universitat Politècnica de València,
46022 Valencia, Spain
2DICATECh—Department of Civil, Environmental, Land, Building Engineering and Chemistry,
Polytechnic University of Bari, 70125 Bari, Italy
3CONSTRUCT-LESE—Faculdade de Engenharia, Universidade do Porto, 4200-465 Porto, Portugal
4FCI—Facultad de Ciencias e Ingeniería, Pontificia Universidad Católica del Perú(PUCP), 15088 Lima, Peru
5DEI—Department of Electrical Engineering and Information Technology, Polytechnic University of Bari,
70125 Bari, Italy; fabio.parisi@poliba.it
6DICAR—Department of Civil Engineering Sciences and Architecture, Polytechnic University of Bari,
70125 Bari, Italy; francesco.fieni@poliba.it (F.F.); nicola.parisi@poliba.it (N.P.)
*Correspondence: valentino.sangiorgio@poliba.it
Abstract:
The building construction sector is undergoing one of the most profound transformations
towards the digital transition of production. In recent decades, the advent of a novel technology for
the 3D printing of clay opened up new sustainable possibilities in construction. Some architectural
applications of 3D-printed clay bricks with simple internal configurations are being developed around
the world. On the other hand, the full potential of 3D-printed bricks for building production is still
unknown. Scientific studies about the design and printability of 3D-printed bricks exploiting complex
internal geometries are completely missing in the related literature. This paper explores the new
boundaries of 3D-printed clay bricks realized with a sustainable extrusion-based 3D clay printing
process by proposing a novel conception, design, and analysis. In particular, the proposed method-
ological approach includes: (i) conception and design; (ii) parametric modeling; (iii) simulation of
printability; and (iv) prototyping. The new design and conception aim to fully exploit the potential
of 3D printing to realize complex internal geometry in a 3D-printed brick. To this aim, the research
investigates the printability of internal configuration generated by using geometries with well-known
remarkable mechanical properties, such as periodic minimal surfaces. In conclusion, the results are
validated by a wide prototyping campaign.
Keywords:
clay 3D printing; sustainable constructions; clay bricks; bricks design; building envelope;
additive manufacturing; printability simulation; periodic minimal surfaces
1. Introduction
The 21st century represents the beginning of the digital transition in the building
production sector. Among the enabling technologies of the fourth industrial revolution,
additive manufacturing is one of the most promising tools to renovate the construction
process with a sustainable perspective [1,2].
Nowadays, 3D printing can be considered a consolidated technology and several 3D-
printed buildings are being developed worldwide [
3
,
4
]. Most of the current applications
and companies’ interests are focused on full 3D-printed buildings. On the other hand, recent
researchers demonstrate the potential of this technology applied for small components
prefabrication [3,5,6].
In the last decade, the area of 3D printing prefabrication has grown with the advent of
a new sustainable technology for 3D printing of clay. The applications of this technique in
the construction sector has attracted interest of both companies and the academic world,
Sustainability 2022,14, 598. https://doi.org/10.3390/su14020598 https://www.mdpi.com/journal/sustainability
Sustainability 2022,14, 598 2 of 15
specifically in the architecture sector [
7
]. A significant research group working on large
blocks realization is the Institute for Advanced Architecture (IAAC). Indeed, IAAC is one of
the first research center that investigated the use of raw earth for construction by employing
massive technological systems destined for the architectural engineering through the
projects Digital Adobe and Terra Performa [
8
,
9
]. Other recent impactful applications of
clay 3D printing (prefabrication of small components) can be classified into three groups:
(1) bricks for non-structural walls and division; (2) building components for sunshades and
cladding; (3) non-structural brick vaults.
(1)
Bricks for non-structural walls and division have been studied by investigating the
external brick geometric freedom to achieve multifunctional behaviors [10].
(2)
Building sunshades and cladding realized in ceramic 3D printing have been investi-
gated in the University of California Berkeley in a broad range of different architec-
tural applications to explore materials like clay in a more technological and creative
way [11].
(3) Non-structural brick vaults to be used as shading systems have been developed in the
University of Minho by Carvalho et al. [12,13].
Beyond the freedom in the external shape, there are few studies regarding the re-
alization of 3D-printed clay components with different internal configurations. Some
preliminary investigations focused on the mechanical [
14
] and energy properties [
15
] of
3D-printed bricks by considering different internal simple geometries [
16
,
17
]. These studies
demonstrate the potential of both mechanical and energy performances and benefit in
sustainability of these new 3D-printed bricks. More in detail, Peters et al. [
15
] argue that, in
3D-printed bricks, the performance is “promising because of the ability to embed different
shapes and sizes of air pockets in the wall”. On the other hand, such studies designed,
printed, and tested regular internal configuration only (internal walls that do not vary their
section along the vertical axis) without investigating complex shapes with difficult print-
ability. Indeed, exhaustive studies exploring the design of complex internal configurations
and consequent limits in printability is still missing in the related literature [5].
This paper proposes a novel conception, design, and prototyping of 3D-printed clay
bricks for building construction to be realized with extrusion-based 3D clay printing. The
sustainability of the clay 3D printing technology is widely recognized and evidenced in
the review of [
5
]. Consequently, the current work presents an important advance in both
knowledge and practice for the application of the sustainable production of 3D-printed
clay bricks.
In particular, the new design realized with a parametric modeling aim to fully exploit
the potential of 3D printing by proposing complex internal geometries in the 3D-printed
bricks. The proposed approach allows overcoming the existing limit of simple internal
geometries experienced in the related literature. Indeed, the external shape is generated
according to the classical bricks (rectangular parallelepiped), while the internal geometries
are developed starting from the well-known periodic minimal surfaces (surface that locally
minimizes its area) [
18
,
19
]. Such geometries are chosen for their well-known ability to
provide effective mechanical properties and energy absorption capability [
20
,
21
]. The
research identifies the most effective internal shape of the bricks to be printed by considering
six different typologies of minimal surfaces and three different configurations of internal
cells with a total of 18 parametric models.
Finite element method simulations are developed by connecting directly the paramet-
ric model with Abaqus software to investigate the printability of such geometries with clay
material. In addition, numerous printing tests are carried out to validate the simulations
and investigate the best printing configuration to reach an effective realization of the bricks.
In conclusion, the research provides useful guidelines to avoid the principal printing
error found and classified during the proposed investigation.
Sustainability 2022,14, 598 3 of 15
The novelties of the presented research are three-fold:
A novel methodological approach based on four phases is proposed to combine
concept design, parametric modeling, finite element method analysis, and prototyping;
A novel conceptual design of a complex brick to be realized with 3D printing and
exploiting ‘minimal surfaces’ is proposed;
The principal printing errors of clay bricks with complex internal configuration are
discussed and useful guidelines are proposed to suggest how to avoid these drawbacks.
The rest of the paper is structured as follows. Section 2proposes the methodological
approach. Section 3shows the results of the novel conceptual design, simulations, and pro-
totyping. Section 4discusses the results and presents suitable guidelines and suggestions
for technicians. Finally, Section 5draws the conclusions.
2. Methodology
The proposed research is developed in four phases: (i) conception and design; (ii) para-
metric modeling; (iii) simulation and printability; (iv) prototyping. Figure 1shows
a flowchart of the four phases of the methodology (in the top left part) and the novel
conceptual design and prototyping of the 3D-printed clay brick (in the bottom).
Sustainability 2022, 14, x FOR PEER REVIEW 3 of 16
The novelties of the presented research are three-fold:
A novel methodological approach based on four phases is proposed to combine con-
cept design, parametric modeling, finite element method analysis, and prototyping;
A novel conceptual design of a complex brick to be realized with 3D printing and
exploiting ‘minimal surfaces’ is proposed;
The principal printing errors of clay bricks with complex internal configuration are
discussed and useful guidelines are proposed to suggest how to avoid these draw-
backs.
The rest of the paper is structured as follows. Section 2 proposes the methodological
approach. Section 3 shows the results of the novel conceptual design, simulations, and
prototyping. Section 4 discusses the results and presents suitable guidelines and sugges-
tions for technicians. Finally, Section 5 draws the conclusions.
2. Methodology
The proposed research is developed in four phases: (i) conception and design; (ii)
parametric modeling; (iii) simulation and printability; (iv) prototyping. Figure 1 shows a
flowchart of the four phases of the methodology (in the top left part) and the novel con-
ceptual design and prototyping of the 3D-printed clay brick (in the bottom).
In particular, (i) in the first phase, the concept design investigates how to include
minimal surfaces in the design of a clay brick realized with 3D printing.
(ii) Successively, the parametric models of the new clay bricks of are generated by
exploiting algorithms-aided design [22].
(iii) In the third phase, an advanced printing simulation is developed in order to iden-
tify the best minimal surfaces configuration and other geometrical parameters suitable for
designing and printing the new bricks. The simulations are obtained by linking the bricks
parametric model with the Abaqus simulation software [23].
(iv) In the final phase, the best printable bricks configurations are selected for effec-
tive prototyping.
Figure 1. Flowchart of the four phases of the proposed methodology.
Figure 1. Flowchart of the four phases of the proposed methodology.
In particular, (i) in the first phase, the concept design investigates how to include
minimal surfaces in the design of a clay brick realized with 3D printing.
(ii) Successively, the parametric models of the new clay bricks of are generated by
exploiting algorithms-aided design [22].
(iii) In the third phase, an advanced printing simulation is developed in order to
identify the best minimal surfaces configuration and other geometrical parameters suitable
for designing and printing the new bricks. The simulations are obtained by linking the
bricks parametric model with the Abaqus simulation software [23].
(iv) In the final phase, the best printable bricks configurations are selected for effec-
tive prototyping.
Sustainability 2022,14, 598 4 of 15
2.1. Novel Conception and Design
The conception of the new printable bricks starts from two ideas:
(a)
The observation of the traditional and widespread brick external shapes and related
regulatory in order to respect the external dimension and the internal wall thickness
(rectangle parallelepiped);
(b)
The use of minimal surfaces to generate the internal configuration of the bricks.
Typically for structural bricks, the length, width, and height can be consistently varied
within the range 15–50 cm, 12–30 cm, and 15–25 cm respectively. The thickness of the
internal walls is considered to be at a minimum 0.8 cm. In addition, the minimum thickness
of the external walls (external shell) is 1 cm with a tolerance of the 10% to consider the
typical imprecision of the production [24,25].
Starting from the above boundaries, the novel conceptual design of 3D printable bricks
investigates how to use minimal surfaces to realize the internal geometry of the bricks. In
particular, periodic minimal surfaces are used in this work because previous research has
demonstrated the advantages of such shapes for 3D printing, including high mechanical
properties, low pressure drop, and elastic-plastic damage [20,26,27].
2.2. Parametric Modeling of Minimal Surfaces and Periodic Minimal Surfaces
In the second phase of the methodology, the parametric models of the new printable
bricks are modeled with the Grasshopper visual programming language (a visual script-
ing and environment that runs within the Rhinoceros 3D computer-aided design). The
parametric modeling of the brick is achieved in three steps: (i) Generation of the external
shell, (ii) generation of the periodic minimal surfaces, (iii) internal shape and finalization of
the brick.
In the following, every step is described in detail by mentioning the specific compo-
nents (in italics) to be dragged onto the Grasshopper canvas.
(i) The generation of the external shell starts from the definition of a rectangle par-
allelepiped by using the components rectangle,extrusion, and cap holes (by respecting the
length, width, and height constraint defined in Section 2.1). By employing the component
centre box and solid difference, the thickness of the external wall is completed. More in detail,
these last two components operate a Boolean difference between the first parallelepiped
and another one with the centre in common, i.e., the same height but reduced width and
length on the basis of the desired thickness.
(ii) In parallel, periodic minimal surfaces are generated through the visual script from
their implicit mathematical equations [
28
,
29
]. The functions are plotted with a domain
of negative and positive
π
exploiting the following grasshopper components: construct
domain,range,cross reference,evaluate, and iso surface of the plugin “millipede” (https://
wewanttolearn.wordpress.com/tag/millipede/ (accessed on 15 February 2021)).
(iii) Once the single periodic minimal surface (single geometry) is generated, it is pos-
sible to create a box array including the obtained geometry to create the internal shape of the
bricks. The vertices in contact of every geometry are joined with the component join meshes
and weld of the “weavebird” plugin [
30
] and the thickness (respecting constraint defined in
Section 2.1) can be created with the components offset mesh of the “pufferfish” plugin.
Once the number of internal cells is defined and geometries have been adequately
scaled (in order to perfectly fit the external shape) with the additional components (division
and domain box connected to the box array), the internal geometry can be joined and finalized
by using the component mesh join. To the sake of brevity, Figure 2shows the visual script
to generate the external shape of the brick, while Supplementary Figure S1 shows the
whole script.
Sustainability 2022,14, 598 5 of 15
Sustainability 2022, 14, x FOR PEER REVIEW 5 of 16
Figure 2. Extract of the visual scripting to generate the external shell of the bricks.
The complete parametric model (Supplementary Figure S1) can quickly change pa-
rameters of the brick—such as dimensions, external shape thickness, and internal geome-
try (changing the mathematical equations and consequently the minimal surface). In par-
ticular, for what concerns the internal geometry, the number of repetitions of the mini-
mum surfaces inside the bricks can be modified in the parametrical model by considering
the number of cells of the box array components.
2.3. Simulations and Printability
The third phase of the methodology is devoted to performing a finite element mod-
eling (FEM) analysis of the printability of the internal cells of the bricks. Such analyses are
aimed to identify the most effective minimum surfaces and the number of repetitions of
the geometry within the brick. The approach is based on an effective plug-in named
VoxelPrint for Grasshopper [23] that can be used to construct simulation files, designed
specifically for 3D printing applications for viscous material, such as concrete. Such plugin
exploits voxelization of the designed three-dimensional shapes into a set of identical finite
elements and it produces ready-to-use input files for simulation in Abaqus. The approach
has been initially developed for concrete printing. On the other hand, in this work, the
material parameters (that can be included in the tool) are modified and adapted to simu-
late clay extrusion instead of concrete. The visual scripting is reported in Figure 3 and the
used components are listed in the following: BerpToVoxel, Material, PrintSetting, VoxelPre-
view, and VoxelToAbaqus.
Note that in order to use VoxelPrint an additional part of the graphical script is needed
to convert the brick geometry in an input file in the form of a B-rep (a solid represented as
a collection of connected surface elements, which define the boundary between interior
and exterior points) [31]. Supplementary Figure S1 shows the whole script.
Figure 3. Visual scripting to create the input files for simulation in Abaqus.
Figure 2. Extract of the visual scripting to generate the external shell of the bricks.
The complete parametric model (Supplementary Figure S1) can quickly change pa-
rameters of the brick—such as dimensions, external shape thickness, and internal geometry
(changing the mathematical equations and consequently the minimal surface). In particular,
for what concerns the internal geometry, the number of repetitions of the minimum surfaces
inside the bricks can be modified in the parametrical model by considering the number of
cells of the box array components.
2.3. Simulations and Printability
The third phase of the methodology is devoted to performing a finite element modeling
(FEM) analysis of the printability of the internal cells of the bricks. Such analyses are aimed
to identify the most effective minimum surfaces and the number of repetitions of the
geometry within the brick. The approach is based on an effective plug-in named VoxelPrint
for Grasshopper [
23
] that can be used to construct simulation files, designed specifically
for 3D printing applications for viscous material, such as concrete. Such plugin exploits
voxelization of the designed three-dimensional shapes into a set of identical finite elements
and it produces ready-to-use input files for simulation in Abaqus. The approach has been
initially developed for concrete printing. On the other hand, in this work, the material
parameters (that can be included in the tool) are modified and adapted to simulate clay
extrusion instead of concrete. The visual scripting is reported in Figure 3and the used
components are listed in the following: BerpToVoxel,Material,PrintSetting,VoxelPreview,
and VoxelToAbaqus.
Sustainability 2022, 14, x FOR PEER REVIEW 5 of 16
Figure 2. Extract of the visual scripting to generate the external shell of the bricks.
The complete parametric model (Supplementary Figure S1) can quickly change pa-
rameters of the brick—such as dimensions, external shape thickness, and internal geome-
try (changing the mathematical equations and consequently the minimal surface). In par-
ticular, for what concerns the internal geometry, the number of repetitions of the mini-
mum surfaces inside the bricks can be modified in the parametrical model by considering
the number of cells of the box array components.
2.3. Simulations and Printability
The third phase of the methodology is devoted to performing a finite element mod-
eling (FEM) analysis of the printability of the internal cells of the bricks. Such analyses are
aimed to identify the most effective minimum surfaces and the number of repetitions of
the geometry within the brick. The approach is based on an effective plug-in named
VoxelPrint for Grasshopper [23] that can be used to construct simulation files, designed
specifically for 3D printing applications for viscous material, such as concrete. Such plugin
exploits voxelization of the designed three-dimensional shapes into a set of identical finite
elements and it produces ready-to-use input files for simulation in Abaqus. The approach
has been initially developed for concrete printing. On the other hand, in this work, the
material parameters (that can be included in the tool) are modified and adapted to simu-
late clay extrusion instead of concrete. The visual scripting is reported in Figure 3 and the
used components are listed in the following: BerpToVoxel, Material, PrintSetting, VoxelPre-
view, and VoxelToAbaqus.
Note that in order to use VoxelPrint an additional part of the graphical script is needed
to convert the brick geometry in an input file in the form of a B-rep (a solid represented as
a collection of connected surface elements, which define the boundary between interior
and exterior points) [31]. Supplementary Figure S1 shows the whole script.
Figure 3. Visual scripting to create the input files for simulation in Abaqus.
Figure 3. Visual scripting to create the input files for simulation in Abaqus.
Note that in order to use VoxelPrint an additional part of the graphical script is needed
to convert the brick geometry in an input file in the form of a B-rep (a solid represented as
a collection of connected surface elements, which define the boundary between interior
and exterior points) [31]. Supplementary Figure S1 shows the whole script.
Sustainability 2022,14, 598 6 of 15
Once imported in Abaqus, the file (generated as the output of the VoxelPrint plugin)
already contains all the configurations to run a non-linear static analysis, useful to evaluate
large displacements on the basis of the considered printing material. Another important
parameter to be set is the “number_of_Steps” used for the definition of the number of
progressive steps of the analysis. Every step represents a portion of the 3D printing process
into which the simulation is divided to evaluate the displacements. In this way, the software
is able to rebuild and simulate the whole printing process.
2.4. Prototyping
The prototyping phase has two purposes: (i) validate the results and the printability
information achieved from the simulations; (ii) investigates some additional errors related
to the limits of the technology in order to create useful guidelines for researchers and
practitioners on how to avoid such specific printing errors.
3. Results
The proposed methodology is applied to investigate the limits of the novel design
of 3D-printed bricks including different internal possible configuration inside a defined
external shell. This section presents the results in three subsections according to the
proposed methodology.
Firstly, a set of 18 bricks are modeled by exploiting the novel conceptual design
(respecting the traditional and widespread brick external shapes) and the parametric
modeling by varying the minimal surfaces and the number of internal cells of the brick.
Secondly, the results of the FEM analysis performed by ABAQUS software are pre-
sented and the best printable configurations are selected (among the 18 bricks modeled).
Thirdly, the results of the wide prototyping campaign are showed, and the validation
of the simulations is discussed. The prototyping involves a total of 18 printings.
3.1. Novel Conceptual Design Results
The generation of the 3D models of the bricks precisely follows the proposed three
steps of the parametric modeling (Section 2.2): (i) generation of the external shell; (ii) gener-
ation of the periodic minimal surfaces; (iii) internal shape and finalization of the brick.
In the first step, the parametric modeling starts from the definition of the external shell
of the brick respecting the traditional external shapes (rectangular parallelepiped). The
current research investigates small brick of 15
×
12.5
×
9 cm since this dimension can be
effectively doubled or tripled to achieve standard brick and block sizes in construction (e.g.,
walls of 30 or 45 cm of width).
In the second step, the minimal surfaces can be generated to create the internal geome-
try of the brick with walls thickness of about 0.8 cm. In particular, six minimal surfaces
are investigated by considering some of the most used surfaces in digital manufactur-
ing [
32
34
]: Gyroid [
28
], Shwarz Primitive [
28
], Shoen’s Batwing [
35
], Battista-Costa [
36
,
37
],
Diamond [29], Sherk tower [38].
In the third step, by exploiting the last part of the visual scripting, it is possible to
combine multiple cells through the box array, assign thickness and automatically scale the
internal geometry to perfectly join the external shell.
Figure 4shows the single cell of minimal surfaces and the combination of many cells
in a box array 2
×
2. More in detail, in the upper part, the figure displays the single cell of
the minimal surface generated by using the proposed visual scripting. In the bottom part
of the image, an example of the combination of multiple cells is showed (in this simplified
illustration, a 2 ×2 box array is considered).
Sustainability 2022,14, 598 7 of 15
Sustainability 2022, 14, x FOR PEER REVIEW 7 of 16
Figure 4. Single cell of minimal surfaces and combination of many cells in a box array 2 × 2.
Once the parametric model is completed with the necessary information, it is possible
to quickly change the internal configuration of the brick by using different minimal sur-
faces and box arrays setting.
As previously mentioned, in this work, 18 printable bricks models are generated by
considering all the combinations of six different minimal surfaces and three different set-
ting of box arrays including the configurations 2.5 × 3, 4 × 5, and 5 × 5.
Figure 5 shows an example of how different configurations of the 3D bricks models
can be investigated by varying minimal surfaces and box arrays.
Figure 5. Different configurations of the 3D bricks: three different box arrays for the Shwarz P and
Gyroid minimal surfaces.
3.2. Simulation Results
With the aim of achieving a complete understanding of the internal brick’s geometry
printability, a series of FEM analyses of bonding is undertaken by using SIMULIA
ABAQUS software. In particular, the printability of the cells is investigated by considering
Figure 4. Single cell of minimal surfaces and combination of many cells in a box array 2 ×2.
Once the parametric model is completed with the necessary information, it is possible
to quickly change the internal configuration of the brick by using different minimal surfaces
and box arrays setting.
As previously mentioned, in this work, 18 printable bricks models are generated by
considering all the combinations of six different minimal surfaces and three different setting
of box arrays including the configurations 2.5 ×3, 4 ×5, and 5 ×5.
Figure 5shows an example of how different configurations of the 3D bricks models
can be investigated by varying minimal surfaces and box arrays.
Sustainability 2022, 14, x FOR PEER REVIEW 7 of 16
Figure 4. Single cell of minimal surfaces and combination of many cells in a box array 2 × 2.
Once the parametric model is completed with the necessary information, it is possible
to quickly change the internal configuration of the brick by using different minimal sur-
faces and box arrays setting.
As previously mentioned, in this work, 18 printable bricks models are generated by
considering all the combinations of six different minimal surfaces and three different set-
ting of box arrays including the configurations 2.5 × 3, 4 × 5, and 5 × 5.
Figure 5 shows an example of how different configurations of the 3D bricks models
can be investigated by varying minimal surfaces and box arrays.
Figure 5. Different configurations of the 3D bricks: three different box arrays for the Shwarz P and
Gyroid minimal surfaces.
3.2. Simulation Results
With the aim of achieving a complete understanding of the internal brick’s geometry
printability, a series of FEM analyses of bonding is undertaken by using SIMULIA
ABAQUS software. In particular, the printability of the cells is investigated by considering
Figure 5.
Different configurations of the 3D bricks: three different box arrays for the Shwarz P and
Gyroid minimal surfaces.
3.2. Simulation Results
With the aim of achieving a complete understanding of the internal brick’s geometry
printability, a series of FEM analyses of bonding is undertaken by using SIMULIA ABAQUS
software. In particular, the printability of the cells is investigated by considering the
Sustainability 2022,14, 598 8 of 15
minimum surface typology and the number of repetitions of the geometry. Consequently, in
the ABAQUS software, 18 simulations are considered including three different dimensions
for every one of the six different minimum surfaces. Such analysis allows to perfectly
simulate the 3D printing setting including both the layer dimension, the thickness of the
extrusion, printing speed and the characteristic of the material.
In particular, the following characteristics are set in the simulation according to the
selected 3D printer and material defined for the prototyping. Note that the used setting
is defined considering the current common features of printers on the market, e.g., Delta
Wasp 40100 for clay. Both material and printing characteristics are defined in VoxelPrint
and reported automatically in Abaqus by the imported model file. The material simulation
parameters are specified in Figure 3, according to the supplier specifications and the related
literature [
39
]. The simulation is also performed consistently with the real machine printing
process: a layer thickness of 1 mm printed by a nozzle of 2 mm diameter and a printing
speed of 30 mm/s.
In addition, some boundary conditions are set in order to consider a simulation
consistent with the whole geometry while analyzing an isolated cell of the different minimal
surfaces. For the continuity of the geometries, in each simulated cell, the orthogonal
displacements of the cell cutting plane are not allowed.
The outcome of the simulation for every cell can be interpreted with three possible
outputs: cell collapse,partial cell collapse, and perfectly printable model.
In particular, the cell collapse refers to an irreversible collapse that generates a necessary
stop of the 3D printing (the collapse is so severe that it does not lead to the positioning of
another layer of material).
The partial cell collapse means that a part of the model suffers a slight collapse during
the extrusion, but 3D printing can theoretically continue. In addition, such criticality affects
the final printed geometry that cannot be exactly the same of the designed 3D model.
In the perfectly printable model, there are no collapses and no significant
local deformations.
Figure 6shows three examples of the FEM results, one for every possible output.
More in detail, the upper part the Figure 6shows the cell collapse corresponding to the
Shwarz P minimal surface in the configuration of a 2.5
×
3 box array. The central part of
the figure shows the partial collapse of a Sherk tower minimal surface in the configuration
of
a 2.5 ×3
box array. The bottom part of the figure shows the effective printable model of
aSherk tower minimal surface in the configuration of a 4 ×5 box array.
In Figure 6, the nodal displacements are highlighted in a chromatic magnitude scale.
In the cell collapse, high deformations (~7 mm) are diffused along the last layer where the
collapse occurs with highest values in the most overhanging portions (~11 mm).
Also in the partial cell collapse, high values of deformations (~9 mm) are detected. On
the contrary, in this case, the large displacements are focused in a very small portion of the
central part of the cell, while the rest of the geometry remains with very low deformations
(~0.07 mm).
The perfectly printable simulation is confirmed by the deformation values of the last
layers (less than 1 mm) about one order of magnitude smaller than the cases of cell collapse
and partial collapse.
In total, the analysis shows that 12 of the cells of the designed 18 bricks could be
effectively printed and one of suffers a partial internal collapse.
Table 1summarizes the printability results of the internal geometries of the 18 designed
blocks obtained with the FEM analysis.
Sustainability 2022,14, 598 9 of 15
Sustainability 2022, 14, x FOR PEER REVIEW 9 of 16
Figure 6. Three examples of the FEM analysis results: collapse, partial cell collapse, and perfectly print-
able.
In Figure 6, the nodal displacements are highlighted in a chromatic magnitude scale.
In the cell collapse, high deformations (~7 mm) are diffused along the last layer where the
collapse occurs with highest values in the most overhanging portions (~11 mm).
Also in the partial cell collapse, high values of deformations (~9 mm) are detected. On
the contrary, in this case, the large displacements are focused in a very small portion of
the central part of the cell, while the rest of the geometry remains with very low defor-
mations (~0.07 mm).
The perfectly printable simulation is confirmed by the deformation values of the last
layers (less than 1 mm) about one order of magnitude smaller than the cases of cell collapse
and partial collapse.
In total, the analysis shows that 12 of the cells of the designed 18 bricks could be
effectively printed and one of suffers a partial internal collapse.
Table 1 summarizes the printability results of the internal geometries of the 18 de-
signed blocks obtained with the FEM analysis.
Figure 6.
Three examples of the FEM analysis results: collapse,partial cell collapse, and perfectly printable.
Table 1. Output of FEM analyses in term of printability of the 18 investigated geometries.
Simulation Results Printability
Minimal Surface Box Array 2.5 ×3 Box Array 4 ×5 Box Array 5 ×6
Gyroid Printable Printable Printable
Shwarz P Geometry collapse Printable Printable
Batwing Geometry collapse Geometry collapse Geometry collapse
Battista-Costa Geometry collapse Printable Printable
Diamond Printable Printable Printable
Sherk tower Partial collapse Printable Printable
Green colour corresponds to “Printable”;
Yellow colour corresponds to “Partial collapse”;
Red colour
corresponds to “Geometry collapse”.
3.3. 3D Printing Prototypes
The last phase consists of the realization of the prototypes of the 18 designed bricks.
The prototyping phase is designed to verify that the FEM analysis effectively simulate
the 3D printing of the bricks and to investigate other unpredictable printing errors. For
Sustainability 2022,14, 598 10 of 15
this purpose, the 18 bricks including six different minimal surfaces and three different
array configurations (box arrays 2.5
×
3, 4
×
5 and 5
×
5) are printed in the FabLab Poliba
laboratory of the Politecnico di Bari (Bari, Italy). In particular, the prototyping exploits the
slicing software Simplify3D and the 3D printer Delta Wasp 40100 for clay. The raw material
used for the printing is clay, a type of fine-grained natural soil material. Table 2shows the
specific mix compositions of the used clay while the percentage of water is 20%. In addition,
the printing laboratory is a climate-controlled room with constant indoor microclimate.
The temperature is around 20 C and the relative humidity is about 60%.
Table 2. Mix composition.
Composition SiO2Al2O3TiO2Fe2O3CaO MgO K2O Na2O CaCo3
3D printable clay 43.8% 15.3% 0.5% 4.1% 11.6% 1.8% 2.6% 1.5% 19.3%
SiO
2
(Silica); Al
2
O
3
(Aluminium oxide); TiO
2
(Titanium dioxide); Fe
2
O
3
(Ferric oxide); CaO (Calcium oxide);
MgO (Magnesium oxide); K2O (Potassium oxide); Na2O (Sodium oxide); CaCo3(Calcium carbonate).
The printing setting includes a layer thickness of 1 mm a nozzle size of 2 mm diameter
and printing speed about 30 mm/s (analogously to the print configuration of the FEM
analysis). The results of the prototyping phase are perfectly consistent with the outputs
of the FEM analyses. To provide some examples, Figure 7shows the collapse,partial cell
collapse, and the brick perfectly printable in the configuration of Shwarz P 2.5
×
3, Sherk tower
2.5 ×3, and Sherk tower 4×5 respectively (the same example of Figure 6).
Figure 7. Collapse (left), partial cell collapse (central photo), and the perfectly printable brick (right).
More in detail, the geometries that collapse according to the FEM model effectively
collapse even in prototyping (in these cases the printing must be stopped). Even the partial
collapse of the Sherk tower 2.5
×
3 occurs as predicted by the FEM simulation. The other
bricks can be easily printed as foreseen by the FEM analysis with the only difference for the
Batista-costa and Gyroyd geometry in the configuration array 5
×
6. Indeed, these geometries
have a complex texture and a very dense geometry (e.g., Gyroid has a very complex shape
and a void ratio of less than 20%) which causes critical printing issues. In particular, the
resolution of the 3D printer is not enough to create the small voids and the extruded
geometry loses its characteristic geometric features (extruded material starts to overlap
even when it should not). This last printing error is named hereafter ‘too dense error’.
Figure 8shows the 18 3D-printed bricks (with different internal geometries) and the
printing result in terms of too dense error,collapse,partial cell collapse, perfectly printable.
Sustainability 2022,14, 598 11 of 15
Sustainability 2022, 14, x FOR PEER REVIEW 11 of 16
More in detail, the geometries that collapse according to the FEM model effectively
collapse even in prototyping (in these cases the printing must be stopped). Even the partial
collapse of the Sherk tower 2.5 × 3 occurs as predicted by the FEM simulation. The other
bricks can be easily printed as foreseen by the FEM analysis with the only difference for
the Batista-costa and Gyroyd geometry in the configuration array 5 × 6. Indeed, these ge-
ometries have a complex texture and a very dense geometry (e.g., Gyroid has a very com-
plex shape and a void ratio of less than 20%) which causes critical printing issues. In par-
ticular, the resolution of the 3D printer is not enough to create the small voids and the
extruded geometry loses its characteristic geometric features (extruded material starts to
overlap even when it should not). This last printing error is named hereafter ‘too dense
error’.
Figure 8 shows the 18 3D-printed bricks (with different internal geometries) and the
printing result in terms of too dense error, collapse, partial cell collapse, perfectly printable.
Figure 8. Prototyping and 3D printing of the 18 bricks and specification of the results in terms of too
dense error, collapse, partial cell collapse, and perfectly printable.
4. Discussion and Guidelines
In recent years, few applications can be found in literature concerning the field of 3D-
printed clay bricks. On the other hand, some research institutes and companies (IAAC
and Wasp) are demonstrating the huge potential of clay 3D printing for sustainable con-
struction [8,9,40,41].
To this aim, this section discusses the characteristics and the differences of the pro-
posed bricks by comparing the proposed ideas and results with previous investigations
[5].
The most relevant research in the 3D printing of large walls and large blocks is per-
formed by Izard et al. [8] in the IAAC institute where cable-driven parallel robots were
applied. More in detail, the IAAC researchers investigated different aspects of 3D-printed
clay building components—including columns [40], bricks, and large blocks with various
types of openings [41]. The IAAC research demonstrated the potential of such technology
and stated the current limits of the application at the large scale. In addition, such inves-
tigation did not delve into complex internal geometries and printability limits since the
focus was directed towards the potential of large-scale applications.
Figure 8.
Prototyping and 3D printing of the 18 bricks and specification of the results in terms of too
dense error,collapse,partial cell collapse, and perfectly printable.
4. Discussion and Guidelines
In recent years, few applications can be found in literature concerning the field of
3D-printed clay bricks. On the other hand, some research institutes and companies (IAAC
and Wasp) are demonstrating the huge potential of clay 3D printing for sustainable con-
struction [8,9,40,41].
To this aim, this section discusses the characteristics and the differences of the proposed
bricks by comparing the proposed ideas and results with previous investigations [5].
The most relevant research in the 3D printing of large walls and large blocks is
performed by Izard et al. [
8
] in the IAAC institute where cable-driven parallel robots
were applied. More in detail, the IAAC researchers investigated different aspects of 3D-
printed clay building components—including columns [
40
], bricks, and large blocks with
various types of openings [
41
]. The IAAC research demonstrated the potential of such
technology and stated the current limits of the application at the large scale. In addition,
such investigation did not delve into complex internal geometries and printability limits
since the focus was directed towards the potential of large-scale applications.
On the contrary, the current proposal investigates small bricks which can be made with
commercial printers, such as the Delta Wasp 40100, for clay. In the field of small 3D-printed
bricks, the first research investigation has been conducted by Cruz et al. [
12
14
] in the
School of Architecture of the University of Minho (Guimarães, Portugal). This Portuguese
research contains the results of more than 3 years of research and provides the evidence
of the performance potential of the 3D-printed bricks, including the freedom to create
customized shapes.
Other investigations confirmed the potential of both geometry and mass customization
in 3D-printed clay bricks for different applications [
42
,
43
] (artistic and architectural) and
multi objective performances [
15
,
44
] (e.g., structural and thermal). On the other hand, none
of these previous studies investigate the possibility and limitations of printing complex
geometries inside bricks [5].
In the current work, firstly a suitable methodology is defined in order to design,
simulate (the 3D printing), and prototype novel complex clay bricks. Secondly, geometries
with well-known remarkable mechanical properties such as minimal surfaces and periodic
minimal surfaces are used to generate a parametric modeling with the novel complex
internal shapes of the bricks.
Sustainability 2022,14, 598 12 of 15
Six different minimal surfaces are investigated in three different internal configurations
(with a total of 18 bricks) in order to identify the most printable configurations.
In conclusion, the most promising geometry is the Diamond, printable in all the in-
vestigated configurations. Moreover, a good printability is also found in the Sherk Tower,
Swarts P, and Gyroyd since these geometries can be effectively printed in different internal
configurations of the bricks. Batwing is the most complex geometry and not suggested to
be effectively printed in a clay brick with the current technologies.
4.1. Guideline for the Design of the Novel Bricks (Avoid Printing Error)
Three different 3D printing errors have been identified in the attempt to print bricks
with complex internal geometries: cell collapse,partial cell collapse, and the too dense error.
The cell collapse configurations occur when internal geometry is increased too much in
size, the cells become large and consequently are difficult to print due to the presence of
larger surfaces with horizontal tangents. The research points out that geometries such as
Diamond,Gyroid, and Sherk tower are less prone to this problem due to their geometry.
The partial cell collapse occurs exactly for the same reason of the cell collapse. On the
contrary, in this case, the cell suffers a deformation only and the printing can be continued
even if the result could be different form the designed 3D model. In this case, the limit of
the cell size has been reached. If the cell dimension is further enlarged, a collapse would
occur. Both partial cell collapse and collapse can be predicted and avoided with the proposed
FEM analysis.
The too dense error differs from the two previous ones because it cannot be predicted
in the FEM analysis. In addition, this error occurs when the geometry is too dense (the
number of arrays is too high and the void ratio decreases reaching the limit of the printing).
In this case, the tolerance and precision of the machine are not sufficient to actually generate
the shape. The extruded material starts to overlap where it should not, and the result is
a fully deformed shape that is different from the original 3D model. This specific error
depends from the printed material and the precision of the 3D printer. Consequently, it
may or may not occur depending on the used technology.
4.2. Limits of the Technology and Future Direction
The presented research, and in particular the prototyping of the complex bricks,
pointed out three technological limits which need to be faced in the future in order to
ensure a sustainable and wide application of clay 3D printing in the construction sector.
The principal drawback found in the experimental phase concerns the printing time
of the bricks. Indeed, the average printing time is about 3 h. The complete overview of the
printing time of the proposed bricks is showed in Table 3. Consequently, the production of
bricks to realize a wall 3 ×4 m may require more than 400 printing hours.
Table 3. Printing time of the 18 bricks.
Minumal Surface Box Array 2.5 ×3 Box Array 4 ×5 Box Array 5 ×6
Gyroid 4 h 27 min 3 h 10 min 4 h 27 min
Shwarz P Geometry collapse 2 h 40 min 3 h 35 min
Batwing Geometry collapse Geometry collapse Geometry collapse
Battista-Costa Geometry collapse 2 h 40 min 3 h 00 min
Diamond 3 h 20 min 1 h 40 min 3 h 20 min
Sherk tower 1 h 50 min 2 h 20 min 2 h 50 min
Green colour corresponds to “Printable”;
Yellow colour corresponds to “Partial collapse”;
Red colour
corresponds to “Geometry collapse”; Black colour corresponds to “Too dense error”.
The second limit concerns the printing of some of the geometries that collapse without
a support [
45
]. In addition, recent studies have demonstrated how spatial 3D-printed
polymer elements can be used to efficiently reinforce 3D-printed geometries [
46
]. Such
intuition of Katzer and Szatkiewicz could be combined with the complex geometries
investigated in the current work to optimize efficiency of clay bricks.
Sustainability 2022,14, 598 13 of 15
The third important limits of current clay 3D printing concern the control of the extru-
sion of the material. The extrusion of the clay 3D printer is affected by small variations in
density of the clay and the mechanics of the printer extruder. These limits lead to insuffi-
cient precision in printing very dense geometries with a low void’s ratio (too dense error). In
this field, it would be useful to improve the existing technology with an automatic extrusion
flow control in order to increase the precision and avoid inaccuracies of the printing.
In addition, in the proposed research, the printing phase is not significantly affected
by the indoor micro-climate since the height of the bricks is very small. On the contrary, in
larger printings [
40
,
41
] temperature and humidity can reduce or speed up the hardening of
the material. To this aim, a future development of the technology can improve the control
on the printing material. An automatic control could correct the extrusion flow and the
percentage of water in the material preparation tank. Consequently, the extruded material
features can be adjusted in real time on the basis of external temperature and humidity to
optimize the printing.
In conclusion, it would be useful to increase the automation of processes, for example
by exploiting the production with 3D printing together with collaborative robots [
47
] to
reduce manpower and the consequent production times.
5. Conclusions
This paper explores, for the first time, the possibility of realizing new 3D-printed
clay bricks for building construction with complex internal geometries based on minimal
surfaces. A novel methodological approach is proposed to design, test, and prototype these
new sustainable bricks including three main steps.
Firstly, the conception and design are established for respecting external dimensions
and internal wall thickness of classical structural bricks.
Secondly, a parametric modeling is developed to realize 3D-printed bricks and to gen-
erate the input files for a FEM simulation in Abaqus suitable for verifying the printability.
Thirdly, a wide prototyping campaign is performed to realize the prototypes of 3D-
printed clay bricks and validate the performed analysis.
In total, a set of 18 brick models are designed, the relative printing is simulated
with a FEM analysis and the effective 3D printings are realized. In conclusion, the most
promising configuration is based on the minimal surface of Diamond, followed in the second
place by Sherk tower,Swarts P, and Gyroyd.
In comparison with previous research, the proposed work demonstrates the potential
of 3D printing in achieving 3D-printed bricks by exploiting different internal configurations
based on the minimal surfaces. In addition, the current research proposes a methodology
for designing and printing by using modern FEM analysis to simulate the printability. On
the contrary, previous experiences are mainly focused on the investigation of bricks for
architectural use only and without the complex internal geometry. Consequently, in the
previous works the simplified geometry did not require the FEM analyses proposed in the
current work to simulate the printability.
This research opens up new sustainable perspectives and possibilities to use 3D
printing for the realization of high-performance 3D-printed brick walls by reducing the
consumption of raw materials and optimizing the internal shape of the brick. On the
other hand, the research emphasizes the need for an improvement of the technology to be
competitive with traditional techniques from a realization time point of view.
Future research will investigate both the structural and thermal performances of the
achieved printable bricks configurations in order to identify most effective ones to realize
high-performance 3D-printed brick walls. Beyond this, another study will investigate the
possibility of modifying the external shell of the brick in order to enhance the combination
of brick 3D printing and the automatic construction of walls with collaborative robotic arms.
Sustainability 2022,14, 598 14 of 15
Supplementary Materials:
The following supporting information can be downloaded at: https:
//www.mdpi.com/article/10.3390/su14020598/s1, Supplementary Figure S1: The complete visual
scripting to generate the bricks.
Author Contributions:
Conceptualization, V.S.; Data curation, V.S. and F.F.; Formal analysis, V.S.
and F.P.; Funding acquisition, N.P.; Investigation, V.S.; Methodology, V.S.; Resources, V.S.; Software,
V.S., F.P. and F.F.; Supervision, V.S. and N.P.; Validation, V.S. and F.P.; Visualization, V.S. and F.F.;
Writing—original draft, V.S.; Writing—review and editing, V.S. and N.P. All authors have read and
agreed to the published version of the manuscript.
Funding: This research and APC was funded by “Fondi Casa delle Tecnologie Emergenti Matera”.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: Not applicable.
Acknowledgments:
A special thanks is addressed to FabLab Bitonto for supporting the development
of the prototype in the laboratory “Fablab Poliba”.
Conflicts of Interest: The authors declare no conflict of interest.
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... Additives used for creation of the special 3D printable concrete mix are in a form of powders and fumes which are usually recycled waste materials (fly ash, slag, ceramic debris, etc.) [13] but they are not of local origin thus force a long-distance transportation. Keeping all above facts in mind one has to weigh the potential of 3D printing to become a highly sustainable construction technology [14]. In authors' opinion only through adopting 3D printing of plastics, the construction industry has the opportunity to achieve the goal of sustainability. ...
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The "Digital Transition" of the building sector and in particular the concrete 3D printing is profoundly changing building technologies and construction processes. However, the materials engineering is still a challenge for the research of even more effective and performing 3D printable concrete. In this context, we analysed magnesium potassium phosphate cement (MKPC) performance as an innovative cementitious material in terms of sustainability and possibility of its use in extrusion-based 3D concrete printing (3DPC). Starting from common formulations present in literature, we discussed the relationship between water to binder ratio and workability in two different quantities of retarders. Some mix compositions were also prepared by replacing sand with rubber aggregates or glass aggregates with the aim of creating lightweight aggregate-based mortars. In addition, the fly ash (FA), a widely material used (but that will not be available in the next few years), was replaced with silica fume (SF). We found that two formulations (samples 2 and 7) show rheological requirements and compressive strengths at 90 min of respectively about 2 MPa and 3 MPa, which are deemed to be suitable for 3D printing processes. Moreover, in sample 7, the use of the expanded recycled glass as aggregate opens new possibilities for reducing the carbon footprint of the process.
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In their fourth decade of development, additive manufacturing technologies are slowly entering research programs dedicated to building materials. While the majority of research effort is focused on using 3D printing of concrete, the authors propose using the technology for creation of spatial plastic reinforcement. Obviously, the strength properties of a 3D printed polymer are much lower than those of steel. Nevertheless, the unconventional spatial shape of a 3D printed reinforcement can substitute for much of the lower mechanical performance of polymer. Flexural characteristics of a cement mortar prism specimen reinforced by hexagon spatial elements were tested and analyzed in this paper. The hexagonal geometric shape was chosen due to its high rigidness. It was proven that it is possible to efficiently reinforce concrete beams by spatial 3D printed polymer elements. Directions of needed research were pointed and discussed.
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Lattice structures find their application across a wide range of fields where strength to weight ratio play a crucial role as in biomaterials. In this paper, we present experimental compressive failure modes of surface based lattice structures with the aim of suggesting the geometry with better mechanical properties that can be used as in fills in components that are 3D printed, thereby reducing its material costs and weight. Lattices based on triply periodic minimal surfaces namely Schoen's FRD and Schoen's OCTO are considered in this study and are developed by polyjet printing. The fabricated structures, after removal of support materials, were tested for compressive strength using a universal testing machine. The methods and results presented in this paper suggest the lattice geometry with better compressive strength that can be used as in fills in 3D printing
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Additive manufacturing techniques, which have been constantly evolving over the past 30 years, have also reached the construction sector, which is often slow in response to innovations. Technologies for the creation of 3D-printed concrete- or steel-structures are experiencing a market launch through the creation of the first printed buildings and bridges. Even though a variety of additive processing methods for ceramic masses have yet been researched, the state of research in the field of ceramic 3D printing for construction applications is lagging behind. This review focuses on the comparison of work in this field completed until summer 2021, as well as to contextualize the topic in relation to 3D printing and ceramic building materials per se. Finally, the findings will be used to identify potentials and strategies that could help the research topic to develop further.
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Computational design allows for architecture with an extraordinary degree of topographical and topological complexity. Limitations of traditional CNC technologies have until recently precluded this architecture from being fabricated. While additive manufacturing has made it possible to materialize these complex forms, this has occurred only at a very small scale. In trying to apply additive manufacturing to the construction of full-scale architecture, one encounters a dilemma: existing large-scale 3D printing methods can only print highly simplified shapes with rough details, while existing high-resolution technologies have limited print spaces, high costs, or material attributes that preclude a structural use. This paper provides a brief background on additive manufacturing technology and presents recent developments in sand-printing technology that overcome current 3D printing restrictions. It then presents a specific experiment, Digital Grotesque project, which is the first application of 3D sand-printing technology at an architecture scale. It describes how this project attempts to exploit the potentials of these new technologies.
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