Congratulations Dr. Petras Vestartas !

On Thursday 30th of September, Dr. Petras Vestartas publicly defended his thesis at EPFL.

He succeeded in his private thesis defense on Monday 5th July 2020 in front of the following expert committee:

Prof Jeffrey Huang, president of the jury
Prof Yves Weinand, thesis director
Prof Niels Martin Larsen, external examiner
Prof Phil Ayres, external examiner
Prof Marco Bakker, internal examiner

Congratulations Petras !

His thesis is of particular importance for the Swiss timber industry. Through combining cutting edge digital technology such as laser scanning with computer modelling and CAD, he proposes a new design to construction methodology for generating raw wood structures with irregular timber. This method is not only potentially widely applicable to a number of fields, but it increases the value of timber that would normally not be considered a useable construction material. It opens up possibilities for the timber industry to move towards an more sustainable and economical business model, as well as encouraging the development of more local, circular economy, which greatly benefits the areas concerned.

Abstract :

Currently, the timber industry in mountain areas exports large quantities of unprocessed lumber and imports finished timber products for local constructions. New digital design-to-production workflows offer a solution by creating new building systems for small-scale local structures using raw-sawn timber. A collaboration with small mountain communes of the Pays d’En-haut in the canton of Vaud has allowed for the development of these new digital processes and the construction of structures with local wood species including pine and spruce.

While a few large robotic companies do focus on raw-sawn-timber fabrication this only leads to a high-level automation of the fabrication process, but does not offer architectural design methods. Architect and fabricator, in the raw-wood context, are two different parties. Advanced architectural research methods, integrated with digital manufacturing, would allow for digitized circular economies independent from the large centralized timber industry. Unfortunately, they focus only on single case-studies without integrating automation in construction or small-scale semi-automated fab-lab methods. The Joinery Solver algorithm Petras developed proposes to revisit individual design-to-fabrication workflows for whole timber structures and propose new open-source, extendable and reusable techniques. It eases the drafting process of pair-wise wood-wood connections linked to design and fabrication, and is based on a design modelling separation into two independent algorithms:

a) shaping methods (macro scale)
b) automation of wood-wood connections (micro scale).

The main design requirements when developing the algorithm were:

a) re-usability of joinery methods for more than one case-study
b) collection of a joinery library from multiple projects
c) design of timber structures with automatic wood-wood connection generation
d) ensuring fabrication constraints and safety
e) interconnect linear elements (beams) and planar elements (plates)
f ) propose an alternative fast graph construction method instead of using a predefined graph data-structure such as Mesh
g) integrate joinery algorithm into a common CAD modelling environment to interconnect with other CAD modelling techniques
h) employ minimal models for a fast computation

The geometrical irregularities of the raw wood require laser scanning and robotic integration. Scanning allows for novel solutions in raw-wood fabrication:

a) point-cloud processing library translated from low-level languages to largely used CAD environment
b) market-less alignment within a robotic setup
c) calibration guidelines for laser-scanners

Robotics allow for a tool-path planning algorithm to shorten the preparation of the fabrication file. The proposed method links the robot reachability and collision detection with timber joint generation. Furthermore, the fabrication of whole timber is interlinked with machining setups. Design recommendations for this setup are given to ensure secure, stable and accurate fabrication, demonstrating that it is possible to detect wood joinery types based on a low-poly architectural model. These models do not require hard-coded parametric models, rendering them applicable to CAD modelling interfaces. The proposed framework considers various types of timber elements, with a particular focus on raw-sawn-timber.

A series of wood-wood connection prototypes were machined using raw-sawn timber to validate the workflow. The methodology evolved into open-source applications that could be employed for raw-wood fabrication: NGon plug-in for joinery modelling and polygonal Mesh processing, Cockroach library for point-cloud processing, IBOIS-CNC G-Code plug-in, 2D packing application – OpenNest and .NET library FaroSharp for Faro Focus S150 laser scanner automation. Moreover, two demonstrators were built to successfully prove the feasibility of the proposed methods:

a) shell structures using side-side connections

b) nexorades using side-end and cross-halving joinery.

c) a truss system from tree forks and multi-valence joinery.

Conclusion

In Petras's thesis, a reusable joinery topology is developed and successfully implemented into several prototypes. The framework is designed to not impose a specific design model while solving local joinery modelling. The point-cloud processing library created during research demonstrates a mark-less shape independent of cloud-to-cloud alignment for robotic fabrication. Also, the modelling framework is interconnected with tool-path planning to manifest the validity of fabrication in regards to joint geometries. The methodology is wholly applicable outside of a closed lab environment, and the proposed software framework is publicly available.