Digitally Designed Stone Sculpting for Robotic Fabrication

Abstract

In this chapter, we present case studies in digitally aided marble sculpting for robotic fabrication developed at the Digital Stone Project workshop. The residency brings together artists, architects, designers, researchers and technologists engaging in state-of-the-art digital tools for the realization of innovative works of art in stone. These projects were developed during the Digital Stone Project research residency during 2013 to 2018 and showcase the potential of novel input methodologies to drive creative processes in design, architecture and the arts. The case studies demonstrate both conceptual and technological development in the design process through 3D modelling, scanning and fabrication workflows, developing toolpaths, virtual reality, haptic interaction and reversible construction techniques. The chapter examines the value of robotic technologies in the design and construction process relative to collaborative crafting of the hand and machine. Accommodating for material tolerances and interrogating the implications of computational crafting in relation to Industry 4.0 and exploring the role of the artisan in machine crafted architectural components.

1 Introduction

Exploration in robotic fabrication has seen a remarkable development in the last decade, particularly in the field of architecture. The democratization of Computer-Aided Design (CAD) to Computer-Aided Manufacturing (CAM) tools led to novel inquiries into the affordances of industrial robotic arms in mass-customization workflows, and their role as potential “all-purpose fabrication machines.” Such renewed interest led to an explosion of research in the field, enabled by the proliferation of dedicated robotic fabrication shops in architecture schools around the globe as well as specific conferences on the topic [1].

However, it could be argued that, with exceptions, the limitations of conducting robotic fabrication in non-industrial contexts may have biased most of the current research to a particular set of outcomes. On one hand, the additional facility requirements to conduct subtractive manufacturing–ventilation, debris disposal, safety measures–may have favored explorations on additive manufacturing, such as 3D printing or assembly operations. Comparably, the costly tooling necessary to perform intense milling operations on harder materials such as stone or metal could have resulted in work focusing on softer substrates such as wood, foam or fresh clay. Consequently, certain forms of robotic fabrication, such as stone carving, have not had the opportunity to be broadly explored.

Intriguingly, the stone carving industry is itself currently undergoing its own new Renaissance, this time powered by the skill of industrial robots [2]. An increasing number of companies now rely on CAD/CAM workflows and robotic fabrication to accelerate their production and remain competitive in a market where material and labor costs are continuously on the rise [3]. Nevertheless, a large portion of their art-oriented production is geared toward the reproduction of existing physical models, typically relying on 3D scan-to-milling processes. The industrial nature of these fabrication processes, combined with the technical literacy necessary to harness the computational frameworks driving it, constitutes a large entry barrier for designers and artists hoping to explore the creative space afforded by these technologies.

1.1 The Digital Stone Project

The Digital Stone Project [4] and Garfagnana Innovazione [5] are a collaborative team to bring together artists, architects, educators and students from across the globe to the historic Garfagnana region of Italy to work with high technology and ancient Tuscan stone. Over the course of a month each participant produces a sculpture or prototype that is carved with a 7-axis robot arm and finished by hand.

This collaboration between designers, technologists and the advanced technology facility at Garfagnana Innovazione has exciting implications for the future of architecture, sculpture and digitally aided design and manufacture. The artists and architects collaborated with robotics engineer Gabriel Ferri to create the computational data that drive the robotic cutting arm. This way of working represents the pinnacle of current manufacturing capability joined with computer aided design (CAD).

Originally designed for automotive and aerospace manufacture, these robots have been coopted to re-invigorate the declining stone industry in the Garfagnana region and to reintroduce the skills associated with marble sculpture [6]. The work includes projects made with generative design, 3D scanning, and 3D programs in animation, CAD (computer aided design), and CAM (computer aided manufacture). Participants wrote algorithms to create the designs for carving or developed projects through interactive computer design programs such as Rhinoceros 3D, Grasshopper, Cinema 4D, 3D Studio Max, and ZBrush.

The work produced in the Digital Stone Project residencies reveals how the development of CAD/CAM and robotics digital manufacturing technologies has helped to reduce the disparity between the geometric forms able to be generated using modern design software, compared to the methods of materializing the outcome. This chapter aims to describe the design and manufacturing processes through 6 case studies of prototypes produced during 2013 to 2018. They explore minimal surfaces, non-standard tool paths, interlocking joinery systems and integrated scanning to milling.

During the DSP residencies one of the greatest challenges facing the engineers to fabricate the digital models is translating the artist's idea into stone through the machine. According to Gabriel Ferri, robotics engineer at Garfagnana Innovazione (2022), “since the idea itself is not linked to the material many times it must be adapted to respect the physical limits of the stone. Finding a compromise between the three parts (1) artist's idea, (2) physical limit of the stone and (3) physical limit of the machine, is the main challenge. To address these challenges the digital stone processing facilities has several resources to help enable and develop solutions. They are described in the following.

1.2 Digital Stone Processing

The state-of-the-art facilities at Garfagnana Innovazione have assisted the participants of the residencies to realise their projects efficiently and in a resourceful manner. The main hardware used is described in the following [7]:

Robotized 3D scanner High performance instrument, suitable to scan both outdoors and indoors. Due to its laser technology, it can reconstruct 3D solid models starting from objects with every form, dimension and complexity. The extreme precision in the survey of points and surfaces assure an exact reconstruction of the scanned object. This instrument, born from 100% Italian research (CNR), can be used manually like a common 3D scanner, but also in synergy with their anthropomorphic robots gaining the skill, unique in this sector, of reconstructing clouds of points independently, without further actions needed on the digital realignment of the scanned model.

Anthropomorphic robots Two robotized stations with two high precision anthropomorphic robots (7 interpolated axes) are the state of the art of technology for the stone processing. The vast working area, up to 2.5 m of height, allow the creation of big and full-round works. Besides the large variety of tools for the processing of every type of marble and stone, there is also the possibility to work materials for the rapid prototyping: plastics, polystyrene, resins, etc. These machines, together with their powerful software, can perform complex operations with extreme efficiency: the results of the creation of human or abstract figures are qualitatively excellent. Progressing from the scale model (created on a PC) to the final realization is now more efficient.

CNC work center CNC work center (5 interpolated axes) to work with blocks, solids and marble slabs, granite, natural stone veneer and glass. It makes every kind of drilling, milling, cutting with blades, contouring, shaping, recessing, polishing, carving, engraving, chamfering, 3d writing and processing. With one of the biggest working areas available, this machine can make big lots with precision and high rapidity.

These facilities have remained for the last few years. According to Gabriel Ferri (2022), while no new tools have been developed, new finishing procedures have been created as a result of the workshop residencies. For example, in the work of Jon Isherwood, “He is very attracted to the gesture of manual finishing, so we tried to translate the human gesture into code for the robot in order to replicate the movements that leave the desired mark on the stone [8].” The workflows are directly impacted by the type of project and will be explained in detail in the case studies. As Ferri states, “Perhaps more than the machines in recent years we have witnessed an evolution of the software. And I believe that in the next few years it will evolve even more because as a user I recognize that there are still many gaps and room for improvement.” The following will describe case study projects and concepts by participants of the Digital Stone Project workshops. These specific projects were chosen for their innovative design to production methodologies specifically relating to the field of construction and Industry 4.0 in the creation of bespoke architectural components. The projects will be discussed in relation to project concepts, digital design workflows, tools and techniques.

2 Minimal Surface Geometries

The first case study project concept uses Minimal Surfaces which are a class of geometric surfaces characterized as having minimal surface area for a given boundary. The classic example is the surface formed by a soap film stretched between a boundary frame [9]. In mathematics, minimal surfaces are defined as ‘surfaces with zero mean curvature” [10]. Zero mean curvature can best be understood as any point on a surface where the lines of principle curvature are equal and opposite. It is possible to compute minimal surfaces like the Catenoid and Helicoid based on parametric equations.

Computational optimization and dynamic relaxation techniques can be used to find minimal energy states for these types of surfaces, instead of generating from a mathematical equation. Interestingly there is a strong correlation between the minimal energy states found computationally via optimization and physical, empirically derived forms [11]. It can be observed these minimal surfaces are operating purely in tension. This study is quite similar to catenary curves found in ‘hanging chain’ models. This makes minimal surfaces also very relevant in the study of tensile fabric structures. It also makes minimal surfaces relevant to the study of forms operation purely in compression, in the form of free-form grids shell structures [12].

The Costa Minimal Surface was discovered relatively recently by Celso José da Costa, a Brazilian mathematician and is used in Case Study 1. The Costa Minimal Surface is rather like a Mobius Strip or a Klein Bottle, where the delineation between the outer and inner surfaces starts to blend. “The Costa surface is a complete minimal embedded surface of finite topology (i.e., it has no boundary and does not intersect itself… Until this surface was discovered by Costa (1984), the only other known complete minimal embeddable surfaces in R^3 with no self-intersections were the plane (genus 0), catenoid (genus 0 with two punctures), and helicoid (genus 0 with two punctures), and it was conjectured that these were the only such surfaces” [13].

2.1 Case Study 1–Costa Minimal Surface (2014)

This project, titled Costa Minimal Surface [14], was designed and fabricated as part of the Digital Stone Project in 2014. Previous research had been conducted in the digital fabrication of tensile structures as well as compression structures. In many of these cases, computational design, simulation and optimization techniques were used to create a digital design, and then computer numerically controlled (CNC) equipment was used to fabricate the final shape. In Case Study 1, a design was created to explore minimal surface geometry using marble instead of in tensile fabric materials. There were three main goals for the design and fabrication of this case study:

Design: From a design perspective, the goal was to explore the interplay between the thinness of these minimal surface ‘soap bubble’ geometries, contrasted with the heavy materiality of stone. It was also very important to ensure the smooth surface continuity was maintained, to help the observer understand the smooth, sensuous curves of the Costa surface geometry.

Simulation/Computation: Case Study 1 required the development of specialized software to support the simulation, analysis and fabrication of the piece. The goal was to create a parametric design workflow to find the desired geometric form in terms of sculptural qualities in order to achieve the design goals above, then support a seamless process of converting the geometry into CNC code able to be executed on the 7-axis industrial arms.

Fabrication: There was also the technical challenge of milling the stone to follow the smooth, thin surfaces of these geometries. It was unknown exactly how thinly the stone could be milled, and if these doubly curved surface topologies could be expressed in stone at all. It was desired to obtain a slightly translucent material quality in the marble, yet still retain the overall structural integrity of the piece by virtue of the fully in compression structural nature of the minimal surface. How the anisotropic nature of marble would interact with the thin shell geometry was also an unknown.

During the design process for Case Study 1, many mathematical surfaces were explored. The Costa Minimal Surface was found to be most suitable for this type of sculpture, given the constraints on the size of the piece and the available fabrication techniques. The software Mathematica [15] was used to explore the surface domain and generate the geometry (see Fig. 1). Online examples for how to compute the Costa function in Mathematica were referenced [16] (Fig. 2)

Fig. 1

Left–Mathematica Software was used to plot the surface–Further refinement of the domain of the surface, Middle Right–Computing the UV Grid [16] Right–Triangulation of surface via the UV grid [16]

Fig. 2

Left–Dynamo Computational Design Software was used to parametrically control the design–simulation loop with Mathematica, Right–Plotting the UV points in Dynamo, refining the edge treatments

A usable geometric mesh needed to be computed from the smooth analytic surface. A grid of points was evaluated in the UV parameter space of the surface and then used to construct a mesh. Online examples were referenced and modified extensively [16]. The software Dynamo (an open-source visual programming tool) was used to create the overall parametric design, simulation and fabrication loop. An open-source Dynamo C# software plugin called DynamoMathematica [18] was developed and used to set input parameters and send data to Mathematica. Once the form was simulated, the geometric mesh was sent back to Dynamo. Special functions needed to be developed in Mathematica to compute the normals for this non-trivial surface. [17] The Dynamo script used the normal to allow thickening the meshed surface and creating NURBS curves based on the UV parameterization (green lines below, see Fig. 3).

Fig. 3

Left–NURBS curves based on the UV parameterization. Middle–Close up showing relationship between the UV parameterization and the meshed surface geometry Right–The final design geometry

Fig. 4

Top: left–fabrication rough block middle–fabrication detail, right–smooth surface, bottom: left: UV lines on surface, middle- UV lines close up, right: final sculpture

The milling toolpaths were created and then run on a 7-axis ABB robot in the mountains of Tuscany as part of the Digital Stone Project at Garfagnana Innovazione. Custom CNC G-Code was developed by Gabriel Ferri to allow the UV lines of ruling to be carved into the surface. The piece was finished by hand using various chisels, grinders and sanding equipment. The following images (see Fig. 4) show the fabrication method and final milled sculpture.

3 Interlocking Joinery Systems Based on Catenary Geometry

The following will describe a joinery system exploring Catenary geometry and is inspired and developed by hanging chain models and catenoids, which are explained in the previous case study the Costa Minimal Surface. However, the design intention of this system was to utilize dry joint connections with interlocking wave geometry. While case study 2−Catenary Tales explores the potential tensile forces of the interlocking wave joinery system, Case study 3− Archi-Twist’ investigates structural stability through the twisted interlocking wave joint.

The waveform prototype joint design was developed through a process of iterative drawing which was then parametrised in Rhino 3D and GRASSHOPPER. One of the most significant aspects of this geometry is that it is made from ‘ruled surfaces’ to accommodate fabrication methods with robotic wire cutting. As a comparison study into EPS foam blocks and natural stone blocks [19] two similar geometries were fabricated with Gosford quarries in Sydney. This prototype demonstrates both potential for column and cantilever structural conditions without the use of extra connectors or mortar, demonstrating reversible construction methods.

3.1 Case Study 2−Catenary Tales (2015)

The concept for the development of ‘Catenary Tales’ (2015) [21] stemmed from an exploration of self-supporting structures in natural stone. The sculptural prototype is made from interlocking wave joinery in varying sizes of modules which engages with the tensile strength of stone. The production process involved the design using 3D modelling software Rhino 3D and manufactured as part of the DSP workshop.

A combination of machined and hand finishes were applied (see Fig. 5) to the sculptural prototype. The overall dimensions are 38 × 36 × 80 cm and weighing at 60 kg in total. The marble type is similar to the colours chosen for Case Study 3– ‘Archi-Twist’ which include Bianco Acquamarina, Venato Orto di Donna and Bardiglio Imperiale. The darker colours at the base while the lighter Carrara marble at the top which further contributed to highlight the complexity of the geometry and material.

Fig. 5

Case study 2 Left–Digital model and assembly sequence, middle–7 axis milling, Right- Final exhibited sculpture

The exhibited prototype ‘Catenary Tales’ was successful in that through the collaboration of the hand and the machine, the realisation of the initial 3D model was achieved. The specific factors which made it successful include the skill of the craftsman in order to remediate the machine inconsistencies and performance with the material. The skill of the fabrication team and technicians to realise the 3D model into physical reality involved many attempts especially when there were cracks and fractures in the material. The workflow of both the modelling and fabrication process could have further integrated methods of material surveying and scanning. However, the focus was on developing the skill of crafting and carving away material from natural stone. Constraints included a limited 25-h machine time for each prototype which affected both the final scale and number of machined parts which were in the end grouped together [20]. The sculptural prototype demonstrates bespoke construction typology with dry joint connections as a contribution towards the innovation of architectural components.

3.2 Case Study 3−Archi-Twist (2017)

The concept of the ‘Archi-Twist’ prototype designed and manufactured as part of the Digital Stone Project 2017 [22] is a twisted catenary arch comprised of innovative modular interlocking wave joinery based on catenary curvature. The method of geometry generation was developed in an entirely parametric environment. In contrast to using sinusoidal or interpolated curvature (used in the initial wave jointed block geometry), catenary curvature for the interlocking wave amplitude has a higher contact surface area thus facilitating a better interlocking capacity. Furthermore, the 180-degree twist of the bases of the arched structure was modelled for both aesthetic and structural reasons due to the extent of the twisting capacity of ruled surface joints. It not only tested the potential capacity of the wave joint contact surfaces but also provided a stabilising mechanism for the overall macro geometry of the arch [20].

Due to limitations in machine time which were 25 h per project within the workshop setting, the scale and number of blocks to be fabricated had to be reduced from 7 parts to 5. Each part (see Fig. 6) was machined in approximately 5 h including tool changes. However, this was still not enough as a final finished module as there was usually 1−2 cm extra material left to sand by hand using the power tools, grinders and hand sanding paper processes similar to processes used by traditional marble sculptors. The overall dimensions of ‘Archi-Twist’ were14 × 66 × 56 cm, weighing at 38 kg in total.

Fig. 6

Case study 3 Left- digital model, middle–fabrication, right–final exhibition sculpture

The above case studies demonstrate the use of bespoke dry joint connections using a specific geometry of the wave jointed blocks which is a developed variation of the osteomorphic block. Modular dry joints in the construction industry have gained acceptance for their versatility and reduced labor costs in comparison to traditional brick and mortar methods. The ease of assembly and disassembly make using connecting blocks for spatial assemblies.

4 Non-standard Tool Paths

A tool path is the direction through space that the tip of a cutting tool follows on its way to producing the desired geometry of the designed work. Nonstandard toolpaths were explored as part of the DSP workshop. The following is an example of a non-standard approach to the development of tool paths and will describe specifically a non-standard method of an engraving toolpath.

4.1 Case Study 4−Orbital Body (2015)

This project, titled Orbital Body, was designed and fabricated as part of the Digital Stone Project in 2015 and exhibited at the Marble Codes exhibition [21]. Orbital Body is a seating element carved from a single block of Bardiglio Imperiale marble and finds novel geometry in the characteristic markings of several different milling passes and tool types. The piece was fabricated through four subsequent machining steps before being hand-finished. As is typical in CNC milling and other fabrication processes, each subsequent machining pass increased in detail and decreased tool size.

This 4 + 1 step procedure moved through the following machining steps: (1) fabrication of a marble block to match the approximate proportions of the piece’s bounding box using a robotically controlled diamond saw, (2) a coarse, flat-end roughing pass which removed the majority of excess material located outside the positive volume of the piece, (3) a ball-end, finishing pass which removed a thin layer of material, closely approximating the curvature and geometry of the digital model, (4) a detailed engraving pass using a ball-end, pencil-neck tool, which inscribed a series of overlapping grooves into the surface of the piece, and (5) the hand-finishing and polishing of the piece to achieve the desired finish and surface texture.

Much of this machining procedure was adapted from standard workflows in CNC-fabrication, however, the detailed engraving toolpath (step 4, above) required a non-standard approach. The engraving toolpaths were produced in Rhino 3D by arraying a series of construction planes along the central mid-line of the piece, intersecting the curved volume of the piece with these planes, and exporting the resulting linework as the engraving toolpath. Originally, the design-intention of the piece was for each engraving toolpath to form a closed loop in space. While this was geometrically possible, the dimensional and rotational limitations of the robot arm made this impossible to fabricate. Working closely with the fabrication engineer, the simulated limit of the robot arm’s rotational “reach” was used to adjust the engraving, surgically clipping the engraving toolpaths in order to remove any areas unreachable by the robot arm.

Despite the technical hurdles in realizing the engraving toolpaths, their contribution to the overall piece is substantial aesthetically and functionally. In terms of the work’s functionality as a seating element, the overlapping engraving lines of the piece impart tooth and friction to an otherwise smooth, slippery, gloss-finished surface. The depth and spacing of the engraving is deepest/densest across the horizontal surface of the seat and is more shallow/sparse along non-seating areas. As the piece was intended for both indoor and outdoor sites, the engraving toolpaths were designed to function as micro-gutters and help to shed water from the seat surface. These engraved grooves, along with the overall slight convex curvature of the seat, allow the seating surface to shed water quickly and prevent the pooling of water in outdoor environments.

The overall form of the piece seeks to capture qualities of speed and continuity to match the smooth, continuous surface quality of the finely-honed stone. Despite this formal aspiration of continuity and fluidity, the piece had to observe two major functional constraints: balance and weight. Viewed in plan (see Fig. 7), the piece is perfectly rotationally symmetrical. Working in Rhino 3D and Grasshopper, each subtle push and pull of the form is matched symmetrically on the opposite side of the form. This allowed for the sculptural, intuitive manipulation of the overall form during design, while maintaining a consistent center-of-gravity and eventually yielding a seating object which resists overturning. The void at the center of the piece also operates functionally. The removal of material at the center of the piece greatly reduces the weight of the final work, allowing it to be moved or adjusted by two people standing at either end of the piece. In future iterations, the central void of the piece might be extracted as a monolithic block, reducing both machining time and material waste.

Fig. 7

Case study 4 Top- 3D model showing the development of toolpaths for engraving, Middle–Plan and section views, Bottom–Fabrication using 7 axis milling

5 Interaction Methodologies and Integrated 3D Scanning to Milling

In this research, we borrow methods and logics from traditional sculpting techniques, and explore their power to be computationally augmented, and to include the agency of the designer in the design and fabrication process. The goal was to showcase the potential of novel interaction methodologies to drive creative processes in design, architecture and the arts.

5.1 Case Study 5−Untitled 50,069,744 (2018)

The first sculpture produced for this research is called “Untitled 50,069,744,” and it constitutes a case study on the use of digital technologies to computationally augment the 3D sculpting process, inspired by the freedom of physical gesturing. The goal for this piece was to create a system that could capture the fluidity of human motion and freeze it in time into a delicate and graceful manifestation. Additionally, the project sought to push the tectonic capacity of the stone to its limits and investigate how thin the sculpture could be fabricated. It was determined that the form of the object would be generated by digitally tracking a human sculptor’s hand, and that these motion steps will be used to generate a self-standing vertical surface to be milled at a specific thickness.

In order to achieve this goal, a bespoke modeling environment was prototyped using Autodesk’s Dynamo (see Fig. 8). The system was able to read physical motion from a hand-held motion controller, and use it to generate a three-dimensional thin solid, with its form was inspired by the undulating shape of a piece of fabric draping over itself. The piece was set to be milled out of a 1800 × 800 × 180 mm block of Arabescatto Vagli, a local marble with gray and golden veins, and an elevated degree of translucency through its main white body. A target thickness of 8 mm was estimated by the manufacturer as an ideal compromise between material stability for fabrication and maximizing thinness for translucency.

Fig. 8

Left–The interactive, hand-based 3D sculpting environment, Right–initial tests

The milling operations were programmed with commercial CNC software, and the sculpture was milled using an industrial robotic arm and an external rotary 7th axis. As the sculpture was created to be publicly exhibited at the Digital Stone Project exhibition [23] a large industrial robotic fabrication space, only one of the sides was manually polished, whereas the opposite side was left with the raw toolpath markings for the fabrication history of the object to remain more readable (see Fig. 9).

Fig. 9

Left−Final sculpture model, Right−Milled sculpture in the shop and the exhibition gallery

5.2 Case Study 6−Dereliction (2018)

The second sculpture produced for this research was called “Dereliction,” and it is a study on the capacity of computational workflows to be adaptive to the physical world and use preexisting conditions as source input in form generation processes. Additionally, the project showcased the potential of digital technologies to mimic certain forms of craft, and the use of algorithms as creative tools. The main question addressed by this work was how digitally augmented sculpting could be harnessed to reclaim discarded materials from marble extractive processes, giving them a second life by adding value through digital craft, while improving the sustainability of the marble extraction process.

To fulfill this vision, an integrated 3D scan to robotic sculpting workflow was developed. A large-scale laser scanner was attached to the robot flange, and a 360° robot scanning procedure was developed to achieve a full three-dimensional representation of the target stone piece. The scanned point cloud was assembled and rebuilt using commercial 3D-scanning software, resulting in a high-resolution polygon mesh. A custom parametric modeling environment was developed in Dynamo, to accept input polygon meshes, representing the 3D-scanned rock, and output the full robotic procedure to groove a custom pattern on its surface (see Fig. 10). The main contribution of the model is the internal translation of the polygon mesh into a graph data structure, susceptible to be analyzed using propagation algorithms, customizable by the designer. Toolpaths were generated using the Robot Ex Machina framework [24].

Fig. 10

Left−Mesh reconstruction, Right−toolpath propagation

For the final piece, a mossy marble boulder abandoned in a nearby creek was reclaimed. The rock was placed on the rotary axis of the robot for scanning, and its position was fixed to avoid calibration errors. The scanned model was post-processed using the abovementioned workflow, and an error-proof robot procedure was generated. A 5 mm diameter milling bit was chosen, and the procedure was successfully run on the robot, taking approximately 2 h to complete (see Fig. 11). No latter treatment or polishing was applied to the piece.

Fig. 11

Left−Fabrication using 7 axis milling, Right−Milling details

6 Conclusion and Future Work

The above case studies demonstrate the value of robotic technologies in the design and construction process relative to collaborative crafting of the hand and machine. The collaborative effort accommodates for material tolerances and interrogates the implications of computational crafting in relation to Industry 4.0, while exploring the role of the artisan in machine crafted architectural components. The case studies investigated both conceptual and technological development in the design process through 3D modelling, scanning and fabrication workflows, developing toolpaths, virtual reality, haptic interaction and reversible construction techniques using bespoke geometry and customized toolsets.

However, the trend towards discrete modular construction must be acknowledged as future work specifically for the case studies with dry joint connections. The use of discrete modularity as opposed to bespoke in interlocking joinery systems in this case rationalises the choice of material and geometry. According to Tessmann, Rossi (2019), “structures are made from discrete and manageable elements that are aggregated in a defined (or rule-based) way. The aggregation becomes a structure if it redirects loads.” While both discrete and bespoke modular blocks consume material, discrete geometry prevents excessive waste generation by limiting the number of variations to the block types to be fabricated and assembled. In bespoke systems each module is individually designed and manufactured, often using more material and labor for the design and production process. Discrete systems only use a limited amount of block variations usually limited to two or three hence can use existing waste material and offcuts, depending on the scale of modules. This is significant in today’s construction sector in line with the Sustainable Development Goals [26] to build resilient infrastructure, promote inclusive and sustainable industrialization, and foster innovation.