Robotic Fabrication

Sutherland

Robotic fabrication of stone assembly details

Section of assembly strategy

3d diagram showing particles, springs and final voussoirs

Geometric variations of joints and tension testing of specimen

6-piece mock-up, interior

6-piece mock-up, exterior

Project Description:

Recently, digital design and fabrication developments in free-form shell structures have flourished, allowing for novel uses of ancient techniques such as stone carving, which can be implemented with contemporary robotic fabrication to customize geometries of discrete parts. The newly available opportunities to digitally design, simulate, and fabricate individually unique shell pieces, or voussoirs, has called into question the modern approach of standardization of components and its complementary ubiquitous joining solutions. However, a significant challenge in building free-form geometries in stone arises from the required accuracy of the joining techniques to accommodate large number of unique voussoirs. One solution to this problem is supporting the pieces in place by means of scaffolding structures while they are tested for fit and manually trimmed (Rippmann et al. 2016). While this is the predominant solution and has produced remarkable structures, the scaffolding results in a costly operation executed by a separate and differently skilled group of fabricators.

This research proposes an alternative assembly strategy for free-form stone shells that relies on a local joining solution at each step of the assembly sequence. Integrating structural analysis with the ability of robots to perform custom non-repetitive stone carving and the ability of cast metal to be formed with great geometric flexibility, the methodology aims to minimize the use of wasteful scaffolding while allowing the adjustable fitting of the resultant voussoirs. The approach incorporates a 5-step process from design to assembly: At each stage of the simulated assembly sequence, finite element analysis is performed to define the exact location, direction and size of the joint needed to stabilize each unique voussoir through tension, compression, bending, or shear. The joint geometry is then optimized to take local forces and is machined to a 1.5mm tolerance with a robotic arm. The assembly is executed by rings following a specific assembly sequence, registering each piece with a custom adjustable drift pin. This process accommodates to the precision needed at each stage of the assembly, allowing deeper or shallower registration in each course and permitting pieces to move and correct until all pieces are fitted in place. The final joint is cast in-situ with a melting point metal, fixing the pieces to their final position. The final results show the specialized assembly joint at each step of the assembly sequence. Two marble prototypes serve as proof-of-concept of the methodology and suggest that the integration of structural evaluation with an adjustable assembly approach enabled by robotic fabrication can reduce the need of scaffolding in the construction of free-form shell structures.

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Faculty:

- Inés Ariza
- Shan Sutherland
- James B. Durham
- Caitlin T. Mueller
- Wes McGee
- Brandon Clifford

Publications:

Affiliation:

Massachusetts Institute of Technology
University of Michigan
Quarra Stone
Matter Design