46 lines
2.3 KiB
Markdown
46 lines
2.3 KiB
Markdown
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---
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name: cad-3d-print
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description: >
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Design, generate, and verify parametric 3D models for 3D printing using code-first CAD (OpenSCAD, build123d).
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scope: global
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---
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# CAD 3D Print
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Design, generate, and empirically verify 3D-printable parts using programmatic CAD.
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Follow the [shared workflow](../../protocols/workflow.md).
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## Workflow
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1. **Dimensional Budgeting & Tolerances**
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- Establish bounding box, mounting points, and mating interfaces from user specifications.
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- Apply standard FDM 3D printing tolerances:
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- **Horizontal hole clearance:** Add `+0.2 mm` to `+0.3 mm` for screw pass-through (e.g. M3 hole diameter = `3.2 mm`; tap hole = `2.9 mm`).
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- **Fit clearances:** Snug/snap fit `0.15 mm`; sliding fit `0.3 mm`; loose/hinged fit `0.4–0.5 mm`.
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- **Wall thickness:** Multiples of nozzle width (minimum `1.2 mm` for 0.4 mm nozzles).
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- **Bed contact:** Add 45° chamfers to bottom edges touching the build plate to prevent "elephant's foot" binding.
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- **Overhangs:** Keep unassisted overhangs $\le 45^\circ$ to minimize support material.
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2. **Parametric Script Generation**
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- Author a standalone, self-documenting OpenSCAD (`.scad`) script:
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- Place all customizable dimensions at the top as labeled parametric variables.
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- Set curvature resolution: `$fn = 60;` or `$fs = 0.5; $fa = 5;` for smooth circular features.
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- Use Constructive Solid Geometry (CSG): `union()`, `difference()`, `intersection()`, `hull()`.
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- Prevent non-manifold coincident faces (Z-fighting): always extend cutting bodies slightly beyond the target surface (e.g., `translate([0, 0, -0.1]) cylinder(h = height + 0.2, ...)`).
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3. **Empirical Verification**
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- **Compile STL mesh:**
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```bash
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openscad -o model.stl model.scad
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```
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Inspect compiler output to ensure `Simple: yes` (a manifold, watertight solid).
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- **Render visual preview:**
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```bash
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openscad --render --imgsize=800,600 -o preview.png model.scad
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```
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- Verify the rendered image to check geometry, clearances, and aesthetic proportions.
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4. **Handoff Artifacts**
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- Keep the editable `.scad` source in the workspace.
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- Provide the compiled `.stl` or `.3mf` for slicing (PrusaSlicer, Bambu Studio, OrcaSlicer).
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- Embed or link the rendered `.png` preview.
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