Design-to-Fabrication Workflow for Raw-Sawn-Timber using Joinery Solver

Abstract

Currently, the Swiss timber industry in mountain areas largely exports unprocessed lumber and imports finished timber products due to the lack of digital tools. By using new digital design-to-production workflows, it is possible to investigate new building systems for small-scale structures using local timber for local applications. While automation in raw wood fabrication is a well-studied field, there is a lack of integration into the local timber industry. In addition, a few large robotic companies focus on raw-sawn-timber fabrication, leading to the high-level automation in fabrication but do not offer any architectural design methods. Architect and fabricator, in the raw wood context, are seen as two different parties. Research in architectural digital manufacturing demonstrate the potential in design with raw timber without the dependence on the large centralized timber companies. Often the focus is given to single case studies without questioning the automation in the local circular economies resulting in the small-scale semi-automated fab-lab workshops. Consequently, it is necessary to revisit individual design-to-fabrication workflows for whole timber structures and propose new open-source, extendable and reusable techniques. First, a joinery algorithm is proposed to ease the drafting process of pair-wise wood-wood connections. The idea of the joinery algorithm is based on a design modelling separation into two independent algorithms: a) global architectural design, and b) local automation of wood-wood connections. These are the principal design requirements for the algorithm: a) re-usability of joinery methods for more than one case study, b) joinery library, c) automatic wood-wood connection generation, d) ensuring fabrication constraints e) propose a fast collision-based graph method, f) integrate joinery algorithm into a common CAD modelling environment, and g) employ minimal models for fast computation. Second, the geometrical irregularities of raw wood require laser-scanning and robotic integration. The Scanning part proposes novel solutions for raw wood fabrication: a) point-cloud processing, b) market-less alignment within a robotic setup, and c) calibration guidelines for laser scanners. The robotic section proposes a tool-path planning algorithm to shorten the fabrication file preparation. The design recommendations for machining setups are given to ensure secure, stable and accurate fabrication. Third, timber joinery prototypes are assembled to validate the proposed workflow. Three types are developed: segmented timber shells, Nexorades and a truss from tree forks. Additionally, the modelling framework is interconnected with tool-path planning to manifest the validity of fabrication concerning a joint geometry. Finally, the developed algorithms are open-sourced. In conclusion, the design-to-fabrication workflow proves that it is possible to detect wood joinery types based on minimal CAD models. From a user perspective, these models do not require hard-coded parametric skills and, as a result, applicable to CAD modelling interfaces. Finally, the integration of the low resolution referencing system of the laser scanner and the industrial robotic arm into the joinery generation method verifies the link between architectural design and manufacturing processes.