The best design alternative was selected for proceeding to the design development and shop drawing generation phase. From the production of the structure’s elements using a three-axis CNC machine, to the final assembly of the elements, students were actively involved in gaining hands-on experience in the digital fabrication process. The final bending-active structure, named "Cavilion", was assembled at the University of Tehran in three days. The term "Cavilion: /kəˈvɪlɪən/" is a linguistic combination of "Cāv: /kʌv/" which refers to the concept of "exploration" and also "concave curvature" in Persian, along with the English word "Pavilion" referring to a structure meant for temporary shelter.

This blend effectively captures the architectural idea of combining aesthetic curvature with a shelter, emphasizing the integration of form and function. Design Methodology: The essence of the Cavilion project is based on the utilization of bending to induce elastic deformations within its structural framework. Through the active-bend methodology, an inventive perspective is introduced to conventional flat-based manufacturing processes. The core objective of this fabrication approach is to achieve a bending-active structure, exemplified by the double-curved surface of Cavilion, which emerges from the elastic deformation of initially planar components.

The rationale for employing the active-bend methodology as the primary approach is predicated on its inherent simplicity in manufacturing planar components, which are subsequently configured into curved elements during the assembly process. Additional advantages encompass the ease of transportation and assembly, and the structure's efficiency in performance and adaptability. Moreover, through the application of elastic deformation, a cost-effective construction becomes attainable for the intricate architecture of Cavilion.

This execution of this project is governed by a holistic perspective that integrates geometric and material considerations from its inception. This integral approach delineates the conceivable design space for the resultant structure. The overall workflow consists of five principal stages described in the following sections. Workshop Process: - Stage 1: Introduction to Computational Design and Digital Fabrication In the initial phase of the workshop, students were introduced to the process of computational design and the commonly used tools in this field.

For this purpose, the Grasshopper3D plugin on Rhinoceros, a 3D modeling software, was employed as one of the prevalent algorithmic design tools. Students learned Python scripting language and its application in architecture using the GH-Python component. After becoming acquainted with the process of design-to-fabrication and several techniques used in digital fabrication, the "Active-Bend" system and "Plywood" material were imposed as design constraints for the students. Due to the hybrid nature of the workshop, half of the students participated in this section remotely. - Stage 2: Form Design During this phase, students were divided into groups of 3 to 5 to work on form design.

Leveraging their knowledge of computational design and the design constraints (active-bending system and plywood materials), each group designed a form with maximum dimensions of 5 * 5 * 3 meters. Based on their software proficiency and thinking approach, students utilized various tools including hand sketching, modeling software, and form-finding plugins such as "Kangaroo" and "Rhino Vault". Students who were participating virtually also shared their design alternatives with others via online platforms.

Among the design alternatives, the one that received widespread approval from the workshop participants in terms of aesthetics, stability, and constructability was selected for further development. In the subsequent step, the chosen form underwent a redesign process led by the instructors. To achieve an optimal form with rational curvature, the form-finding method known as "Dynamic Relaxation" was employed using the "Kangaroo" add-on within Grasshopper. - Stage 3: Design Development To prepare the form for digital Fabrication, a BIM model including the detailed 3D model of the elements (LOD 400) and related information regarding each part is needed.

This process was carried out by the instructors using the Grasshopper plugin. Due to the complex curvature of the form (anticlastic), its surface was not developable and could not be flattened without distortion. Therefore, the form was divided into narrow and expandable strips to increase its constructability. To maintain stability and curvature, the structure was designed in two main layers consisting of strips perpendicular to each other (i.e., radial and peripheral). However, due to the limitations of the available CNC cutting machine, the strips had to be divided into smaller pieces to fit within the length limit of the machine (240cm).

This division resulted in gaps in different parts of the form, which compromised the continuity of the curvature. To address this issue, a third layer was added, consisting of short pieces used as reinforcement patches at these weak points. To connect these three layers, screws were used at the overlapping points. The holes required for the screws were incorporated into the 3D model and subsequently cut by the CNC machine. In bending-active structures, ensuring the proper connection between the structure and the ground is crucial for maintaining the curvature and stability of the structure.

Therefore, a base plate and support parts were also designed. Similarly, due to the limitations of the CNC machine's dimensions, the base plate had to be divided into smaller parts, and a series of reinforcement patches were added to enhance its strength. Due to the intricate geometrical complexities of the form and the unique division of strips, every element had a distinct shape, as well as a specific placement for connecting to other pieces. To ensure clear identification and readability of the parts, a unique name, and related connection numbers were assigned to each element.

These numbers would be used for coordinating the fabrication and assembly process. The final step in the design development process involved generating shop drawings needed for the CNC cutting process. The 3D strips, their holes, and their related tags were unrolled and nested in plywood sheets. The same process was applied to the supporting parts as well. Using "ArtCAM" software to define parameters such as drill type, material thickness, cutting speed, cutting steps, etc., the CNC cutting toolpath (G-Code) was generated.

The main strips of the form were cut from 6 mm sheets, the support parts from 15 mm sheets (double-layered), and the support plate from 18 mm sheets. Considering the construction technique of active bending, the thickness of the elements played a crucial role in the fabrication process. The material thickness was determined through structural analysis using Karamba. The highest curvature (1.7) happens at the top parts of the form, corresponding to a circle with a radius of about 60 centimeters. Given the mechanical properties of Plywood, various calculations were conducted; It was observed that the 6-mm thickness satisfied the structural requirements: a uniform live load of 1.5kN/m2 in addition to its weight. - Stage 4: Fabrication Process The fabrication process of this project involved in-person participation of all students.

It started with cutting the elements from plywood sheets based on the prepared toolpath file (G-code) using a 3-axis CNC machine. Once each part was produced, the corresponding name and connection numbers were written on it. After the initial drilling process by the CNC, the students took on the responsibility of secondary finishing for parts using different equipment such as sandpaper to achieve smooth finishing. Also, to enhance the durability and resilience of the elements against environmental factors like moisture and UV rays, a paint coating was applied.

Although the digital model represented all the parts in a bent state, the parts were initially produced in a flat form. The final bent shape would be achieved by connecting the parts using the designated connection points. - Stage 5: Assembly Process The assembly process was initiated with the installation of the base plate and supports. This step facilitated the positioning and installation of the strip elements. Guided by the weave map obtained from the Grasshopper model, the assembly process began from the supports and areas with the least curvature, gradually progressing toward the areas with the highest curvature.

This systematic approach ensured a smooth and efficient construction process. The fabrication of the "Cavilion" structure took place over three days on the Campus of the University of Tehran. With the completion of this step, the physical manifestation of the pavilion became a reality. Credits (in alphabetical order for each section): -