Manufacturing | Suspended Ceilings - Algorithmic Sheet Metal Folding with Rhino.Inside
We engineered a computational geometry engine that automates the complex unfolding of bespoke ceiling panels. By implementing neutral axis algorithms and a headless Rhino backend, the tool transforms 3D design models into fabrication-ready flat patterns in milliseconds.
- Client
- Private Client
- Timeline
- 2025
- Service
- Computational Design→
The Engineering Challenge
The client, a global leader in suspended ceilings, relied on a manual 2D AutoCAD workflow that was struggling to keep pace with demand. Their internal CAD technicians needed to design complex, custom ceiling systems - accounting for seismic bracing, wind loads, and intricate grid layouts - using only standard drafting tools. The goal was to automate this process. However, standard AutoCAD APIs lacked the geometric computational power to handle complex surface intersections and real-time 3D visualization. The solution required a paradigm shift: an application that could "think" in 3D logic but deliver standard 2D AutoCAD drawings.
The Solution Architecture
We engineered the Sheet Metal Folding API, a domain-driven computational engine built on Rhino.Inside. It bypasses the limitations of standard CAD tools by performing unfolding calculations in a platform-agnostic geometry layer before generating output.
Neutral Axis Algorithms
The core innovation is the mathematical modeling of the bend itself.
- Bend Allowance: We implemented algorithms to calculate the exact arc length consumed by each fold based on the material's specific K-Factor (ratio of neutral axis position).
- Solving Plane Strategies: Using the Strategy Pattern, the solver dynamically applies different coordinate systems for Convex, Concave, and "Flipped" bends (reflex angles >180°), ensuring accurate geometry regardless of panel topology.
Five-Phase Pipeline
The engine operates as a linear transformation pipeline:
- Topology Analysis: Validates manifold geometry and builds an adjacency graph of all faces.
- Tree Construction: Organizes faces into a hierarchy rooted at the largest surface.
- Fold Calculation: Computes the neutral axis arc and Outside Setback (OSSB) for every edge.
- Flat Pattern Assembly: Recursively traverses the face tree, applying transforms to lay out the 2D pattern.
- Output Generation: Produces 2D cutting curves (DXF ready) and a 3D validation model via Boolean union.
Three-Tier Geometry Abstraction
To ensure robustness, we architected a strictly layered geometry system.
- Internal Types: All physics and math calculations occur in our custom lightweight geometry library (AWI.RhinoInside.Interop), ensuring zero dependency on the CAD platform during calculation.
- Rhino Kernel: We only call RhinoCommon for complex Boolean operations (like merging thickened solids), keeping the core logic fast and testable.
- CAD Output: The final result is converted to native AutoCAD entities only at the very last step.
The Result
The tool transformed a manual engineering bottleneck into a background task.
- Speed: Unfolding time dropped from ~20 minutes to <1 second per panel.
- Scale: The system can process an entire project's library (500+ panels) in under 5 minutes.
- Accuracy: By codifying the K-Factor logic, the tool eliminates human calculation errors, reducing material waste on the factory floor.
- < 1s
- Folding Time Per Panel
- 17+
- Material Profiles Supported
- 5-Phase
- Transformation Pipeline
- 100%
- Neutral Axis Accuracy