💡 What’s customizable?

All key dimensions are exposed as parameters in the Customizer:

Big side (bottom)

• Size mode – choose whether you enter the inner or outer rectangle (width & height)
• Width & height – rectangular size in X/Y
• Corner rounding – outer corner round diameter (for smooth, rounded corners)
• Straight length – length of the big rectangular section

Small side (top)

• Size mode – choose whether you enter the inner or outer rectangle (width & height)
• Width & height – rectangular size in X/Y
• Corner rounding – outer corner round diameter, independent from the big side
• Straight length – length of the small rectangular section

Transition section

• Wall thickness – uniform wall thickness for both big and small sides
• Transition length – length of the tapered transition between the two rectangles
• Bend angle – angle between big and small sides
  • 0° = perfectly straight
  • positive/negative values tilt the outlet in either direction
• Bend direction – rotate the bend around the main axis so the elbow points exactly where you need it

The transition uses a smooth, skewed hull between rounded rectangles so it stays fully closed even at an angle.

🖨 Print recommendations

Orientation

• Print standing on the big side, as shown in the render.
• This gives strongest walls along the airflow direction and best dimensional accuracy on the duct faces.
• For moderate bend angles (≤ ~45°), the inner transition usually prints fine without internal supports; check your slicer preview.

Settings

• Layer height: ~0.20–0.24 mm
• Walls / perimeters: 3–4 perimeters for a strong, airtight shell
• Infill: 20–30% grid/gyroid is plenty for most duct adapters
• Top/bottom layers: 4–6 layers to avoid pinholes

Material

• PLA – fine for indoor, normal-temperature fresh-air systems
• PETG / ABS / ASA – better for warmer air, boiler rooms, attics, or where a bit more toughness and heat resistance is needed

✅ Notes

• If matching to an existing duct or flange, set the inner size slightly larger than the real duct OD for a slip fit,
  or slightly smaller if you want a press fit and your material has some flex.
• Corner rounding not only looks nicer but reduces turbulence and is easier to clean.
• Because both sides can be defined as inner or outer sizes independently, it’s easy to adapt between:
  • metal ducting ↔ plastic ducting
  • nominal inch sizes ↔ metric sizes
  • tight slip fit ↔ loose “over” sleeves.