Parametric Duct Reducer

This parametric duct reducer is designed to connect one round duct size to another without having to hunt down the exact off-the-shelf adapter you need. The model supports adjustable upper and lower duct diameters, shell thickness, neck lengths, overall height, and fillet settings, making it useful for adapting duct runs where size, space, or fitment constraints vary.

It works well for ventilation, exhaust, dust-routing, and other airflow setups where a standard reducer is close but not quite right. Instead of redesigning a transition piece from scratch, you can tune the dimensions to match your ducting and print an adapter that fits your specific setup.

Printing Tips

Printing Technology: FDM
Layer Height: 0.2 mm
Perimeters: 4
Infill: 10%
Infill Pattern: Gyroid
Recommended Material: PLA, PETG, ABS
Supports: No
Support Type: None

Notes:
- Increase the overall height to create a gentler transition and reduce overhangs.
- PETG, ABS, or another temperature-appropriate material is recommended for warm or demanding environments.
- Confirm that the selected material is suitable for the operating temperature and application.
- Do not use the printed reducer for combustion exhaust, flues, or other code-regulated applications.

Assembly Instructions

Recommended Materials:

• Ducting or hose
• Recommended: Nashua 324A HVAC Foil Tape
• Tested: Nashua 367-17 FoilMastic
• Optional hose clamps or mounting hardware

Disclosure: As an Amazon Associate I earn from qualifying purchases.

Materials Notes:
I tested the reducer with Nashua 367-17. It seals extremely well, but it is ludicrously overpowered for most installations.

Instructions:

1. Measure both duct connections. Use the inside or outside diameter based on how the reducer will fit.
2. Enter the diameters, allow for print clearance, then print and clean up the connection surfaces.
3. Dry-fit both ends. They should seat securely without excessive force.
4. Connect the ducting and seal each joint with HVAC foil tape. Add hose clamps if needed.
5. Support the ductwork, run the system, and check for movement or air leaks.