3. Computer Controlled Cutting

Global Class

The global session introduced the fundamentals of computer-controlled cutting, with a focus on laser cutters and parametric thinking.

Basically I can summarize it as assigning a numeric value to a parameter. Then all changes are correlated automatically. These are not only values, but can also be materials, number of elements, equations, expressions, etc.

One of the few memorable moments was a simple sketch explaining kerf: the material removed by the laser beam, and how even fractions of a millimeter determine whether a joint fits tightly or falls apart.

The other points to remember was a presentation by Jeff Ritchie’s project which mentioned geodesic domes. That ignited an interchange and mentioned Buckmister Fuller, dymaxion car and house which led me to research into that area as it was part of my exploration/discovery journey from last week.

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Reflection on the session

The content itself was probably firs-class, but the delivery format was disengaging. In a medium like Zoom, one-way explanations from presenter to participants with little interaction was not attractive to me. Long lists of machine specifications and settings were presented in sequence…

Personally, it highlighted the outdated pedagogic methods that are engrained in our idea of education.

Local Class

The local sessions shifted the focus from theory to practice. Instead of listening to specifications and terminology, we began drawing, adjusting parameters, and producing physical results.

Parametric sketching in Fusion

We started with a simple comb-like press-fit test piece.

The objective was to:

• Define slot width as a parameter
• Duplicate elements using patterns
• Adjust dimensions globally through variables

This introduced the core idea of parametric design:
one value changes, the whole system adapts.

The comb was an exercise to understand material thickness, kerf, and press-fit tolerances.

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Parametric modeling in Rhino + Grasshopper

We then moved to Rhino and Grasshopper to explore visual parametric workflows.

Instead of sketch constraints: • Geometry was generated through node-based logic.
• Sliders controlled dimensions in real time.
• Shapes updated instantly as parameters changed.

This made the parametric logic more visible and intuitive.
The relationship between numbers and form became explicit.
We came to the conclusion that parametric modelling in Rhino is drawing programming.

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### Laser cutter introduction and lab practice

In the lab, we were introduced to the actual machines by Shyam.

• Material loading
• Focus adjustment
• Safety procedures
• Cutting tests

This was the first moment where the digital model met physical reality.

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Parametric thinking in other tools (Blender)

We also explored parametric approaches in Blender.
This was the least interesting session for me, as I couldn’t follow the flow behind Blender, at least in a remote fashion which was the case.

My Parametric design

Initial idea

The goal was to design a lightweight hood structure made from flat plywood sheets and assembled through press-fit joints.

The starting concept was:

• A rectangular base frame
• A series of vertical ribs
• A curved dome shape created by repeating those ribs along the base

This required the geometry to be:

• Fully defined by parameters
• Adaptable to material thickness and kerf
• Organized for efficient laser cutting

The hood was treated as a system of relationships between each of its parts.

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First parametric rib

The process started with a single rib:

• A half-circle profile
• A flat tab at the bottom
• A slot that would connect into the base

Key parameters were introduced:

• thickness
• base_depth
• slot_width
• rib_height

This allowed the rib to:

• Change height
• Maintain the correct slot size
• Stay compatible with the base automatically

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From one rib to a graded dome

Instead of using 15 identical ribs, the design evolved into a graded dome.

The idea:

• The tallest rib at the center
• Progressively lower ribs toward the sides
• A limited number of unique heights, repeated symmetrically

Four height parameters were defined:

• rib_height_01 (tallest)
• rib_height_02
• rib_height_03
• rib_height_04 (shortest)

This transformed the structure from a simple tunnel into a parametric shape system.

I then used 3D visualizations in Fusion to test different rib counts and observe how the form changed, which was the advantage of working with parameters.

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Adapting geometry

During the process, several adjustments were necessary.

The rib was initially defined by a fixed radius.

Once the slot geometry was added, the arc no longer matched the required base span.

Instead of forcing the span:

• The arc height became the driving parameter
• The slot geometry became the primary reference

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Preparing the laser-cut layout

Once the rib variations were defined:

• The different ribs were duplicated to reach the required quantity, which was 15 in total
• All ribs were arranged in a flat layout
• The base frame with slots was placed on the same sheet

At this stage, the design existed as:

• A parametric system in Fusion
• A flat sheet layout for fabrication
• A 3D preview to understand the final form

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Iteration, errors, and adjustments

As the model evolved, the process became about resolving constraints that I didn’t take into account at the start of the design.

Each step introduced small conflicts:

• Arcs that no longer matched the base span
• Slots that didn’t align with the ribs
• Profiles that wouldn’t close
• Extrusions that produced disconnected bodies
• Patterns moving in the wrong direction
• Components rotating around the wrong axis

The workflow became cyclical:

1. Modify a parameter
2. Break the geometry
3. Understand the failure
4. Rebuild the relationships
5. Test again

Key adjustments included:

• Redefining the rib from a fixed radius to a height-controlled arc
• Making slot geometry the primary reference
• Rebuilding the base to include all slots correctly
• Rotating and patterning ribs for a full dome preview

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Structural pivot and simplification

At a certain point, the slot logic and overall structure became too complex and fragile.

With guidance from Dani, the design was simplified:

• Base system and how ribs attached to it
• Adjustments in widths, thickness, kerf, etc.
• Independent rib components
• Simpler assembly logic

The design shifted from a visually complex form to a simple structurally coherent system.

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Press-Fit Structure — Design Development

Once the ribs, tabs, base, and slot system were defined for a press-fit assembly, I began experimenting with different arc geometries to explore both structural and aesthetic variations.

The initial versions were more angular and mechanical. These were useful to establish dimensions, tolerances, and the logic of the press-fit joints.

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Exploring Alternative Arc Forms

After the basic system worked, I explored more conic and curved profiles directly in Fusion.
These shapes felt more attractive and better aligned with the intended concept:

• More aerodynamic and fluid
• Better suited for a hood-like structure
• Occupies less visual and physical space
• Potentially lighter while maintaining strength

Because the model was built parametrically, the new shapes could be applied across the structure without rebuilding everything.

Using rectangular patterns, the ribs could be duplicated and spaced consistently while preserving the press-fit logic.

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Layout for Fabrication

After finalizing the rib geometry, I prepared the layout for cutting.

Steps followed in Fusion:

• Extruded all bodies to the required thickness
• Transformed all bodies into components
• Created a sketch to represent the stock sheet
• Opened Modify → Arrange

Objects tab - Components → select all rib and base components

Envelopes tab - Choose Sketch/Face - Select the stock rectangle sketch

Spacing - Object spacing: 3–5 mm

Once the layout was complete, the file was exported and saved in Rhino format to prepare it for the laser cutter workflow.

The next step will be the actual laser cutting and testing of the press-fit assembly.

Work in progress…

Vinyl Cutting Exercise

Local Class Demonstration

The vinyl cutting process was first introduced during the local class.
Our instructor demonstrated the complete workflow, from preparing the design to sending it to the cutter. The emphasis was on understanding the relationship between vector graphics and machine instructions.

The demonstration showed:

• Preparing a clean vector file
• Adjusting scale and line properties
• Sending the design to the vinyl cutter
• Weeding and transferring the final sticker

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Sketching the Design

For my own vinyl exercise, I worked together with my daughter.
She created a hand-drawn sketch on paper, which we decided to convert into a vinyl sticker. This made the exercise more personal and helped connect the digital workflow back to a physical, manual starting point.

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Digitizing the Drawing in Inkscape

The sketch was photographed and imported into Inkscape.
Using the Trace Bitmap tool, the image was converted from a raster photograph into vector paths suitable for cutting.

Steps followed:

1. Import the photo into Inkscape.
2. Select the image.
3. Open Path → Trace Bitmap.
4. Use Brightness cutoff to generate a black-and-white vector.
5. Adjust threshold until the lines were clear.
6. Apply the trace.
7. Delete the original raster image.
8. Resize the vector to the desired sticker size.

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Preparing the File for the Cutter

The lab uses Silhouette Studio to control the vinyl cutter.
However, the basic version of the software does not support SVG files, which created an unexpected step in the workflow.

Steps taken:

1. Download and install Silhouette Studio.
2. Attempt to import the SVG file.
3. Discover that SVG import is disabled in the basic version.
4. Return to Inkscape.
5. Export the design as:
6. Desktop Cutting Plotter (AutoCAD DXF R14) (.dxf)
7. Open the DXF file successfully in Silhouette Studio.

Use of AI Tools

AI was used as a technical assistant during the design process.
Its role was to help with parametric logic, formulas, constraint strategies, and troubleshooting inside Fusion.
All geometry, modeling decisions, and fabrication steps were executed manually.

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ChatGPT – Parametric logic and troubleshooting

Example prompts

Act as a Fusion 360 expert and help me calculate parameters for slot spacing on a laser-cut base.
The base has a fixed length, edge margins, and a defined number of ribs.
Provide the correct formula so the spacing updates automatically when rib count changes.

Help me structure a parametric rib system where height, slot width, and material thickness are controlled by parameters.
The goal is to keep all parts compatible when thickness or rib count changes.

AI responses were interpreted and adapted to the actual Fusion model rather than copied directly.

Midjourney – Early concept visualization

Used to generate quick concept images showing the intended structure before modeling.

Prompts uses

laser-cut metal hood structure for a rectangular base frame with slots, series of curved ribs forming a protective canopy, press-fit joints, flat-pack components shown separately and assembled above, technical exploded view, clean industrial design, plywood material, workshop context, soft neutral lighting, minimal background, product design sketch style –ar 4:3

laser-cut plywood hood structure, rectangular base frame with evenly spaced slots, series of ribs forming a graded dome, tallest rib at center, shorter ribs toward edges, press-fit joints, visible tabs and slots, workshop environment, soft natural light, realistic plywood texture, minimalistic design, technical product photo –ar 16:9

Purpose

• To visualize the overall idea before modeling.
• To communicate the intent of the structure.
• Not used for dimensions or fabrication decisions.