# Corner Decoration — Design Spec

**Date:** 2026-06-11

## Overview

A 1-meter-tall decorative piece for a 90° wall corner. Twisted flat ribbon blade emerging from a hollow triangular spine. Split into 4 × 25cm 3D-printed pieces. Cable routing channel through the spine.

## Geometry

### Overall
- Total height: 1000mm (4 × 250mm pieces)
- Corner angle: 90°
- Ribbon protrusion: 80mm from corner to ribbon centre axis (along 45° diagonal); ribbon extends 50mm either side → near edge at 30mm, far edge at 130mm from corner
- Twist rate: 360° per 250mm piece (ribbon returns to same orientation at each joint)

### Ribbon Blade
- Width: 100mm
- Thickness: 4mm
- Cross-section: flat rectangle (blade / ribbon profile)
- Path: helical, centered on the 45° diagonal axis of the corner
- One full twist (360°) per piece — top and bottom faces of each piece are geometrically identical

### Triangular Spine
- Profile: right isosceles triangle, legs ~20mm × 20mm
- Sits flush in the 90° corner; hypotenuse face at 45° to both walls
- Two flanges (~5mm thick, 20mm wide) extend along each wall surface for gluing
- Cable channel: 12mm diameter circular hole through the centroid of the triangle, running full height
- Ribbon attaches at the midpoint of the hypotenuse face

### Piece Joinery
- Alignment peg: 4mm square peg on top face, matching socket on bottom face
- Cable hole aligns automatically via peg
- Pieces glued wall-to-wall and to each other with construction adhesive

## Print Settings

| Parameter | Value |
|-----------|-------|
| Orientation | Vertical (upright) |
| Supports | Required (ribbon overhangs during twist) |
| Layer height | 0.15mm |
| Infill | 15% gyroid |
| Material | PLA |
| Pieces | 4 identical pieces |

Fallback if supports leave bad finish: split each piece into spine + ribbon, print separately, glue.

## Generation

Python script using **cadquery**. All dimensions as named constants at top of file. Outputs one STL per piece (all 4 identical).

### Key construction steps
1. Build spine: extrude right-isosceles triangle profile × 250mm, subtract 12mm cylinder for cable hole, add flanges on two legs
2. Build ribbon: sweep a 100mm × 4mm rectangle along a 250mm helix path (pitch = 250mm for 360°/piece), centered on the 45° diagonal axis
3. Boolean union spine + ribbon
4. Add alignment peg (top face) and socket (bottom face)
5. Export STL

### Parameters (all tunable)
```python
PIECE_HEIGHT     = 250   # mm
NUM_PIECES       = 4
RIBBON_WIDTH     = 100   # mm
RIBBON_THICKNESS = 4     # mm
PROTRUSION       = 80    # mm — corner to ribbon centre axis along 45° diagonal
TWIST_DEG        = 360   # degrees per piece
SPINE_LEG        = 20    # mm — triangle leg length
FLANGE_WIDTH     = 20    # mm
FLANGE_THICKNESS = 5     # mm
CABLE_HOLE_DIA   = 12    # mm
PEG_SIZE         = 4     # mm square
PEG_HEIGHT       = 5     # mm
```

## Mounting

- Glue flanges to both walls with construction adhesive (e.g. Liquid Nails)
- Stack pieces bottom-up, aligning pegs
- Thread cable through spine channel before gluing upper pieces
- No visible hardware