Popular fittings › Backdraft flap
Backdraft flap
A separately printed gravity flap, captive hinge and hard opening stop. Free 3D printable.
Open in the designer →
Opens with the sizes below. Change anything, then export 3MF, STL or STEP. Free, no account, runs in your browser.
Starting sizes
| End | Inner size | Connection |
|---|---|---|
| Inlet | 63 mm (2.48 in) | Smooth sleeve |
| Outlet | 63 mm (2.48 in) | Smooth sleeve |
Need another size? Every dimension is editable in the designer, in millimetres or inches.
What it is
Lets air out but closes by gravity when the fan stops, keeping outside air from coming back in.
How to measure
For each end, measure the hose, pipe or port it joins with calipers. If that part slides into the fitting, measure its outside diameter and keep “Measure by: Inner diameter”. If the fitting slides into a hose, measure the hose’s inside diameter and switch to “Outer diameter”. Measure twice across the circle; flexible hose is rarely perfectly round.
Print tips
- The export already places every component in its recommended print orientation. Keep supports off sleeves, sockets and any sliding or tight-fit surface so they stay smooth; if your slicer asks for supports, paint them only where an outside overhang needs them.
- Moving parts print separately; keep their sliding and turning faces free of supports and brim so they move freely.
- Assemble it and test the motion by hand before connecting hoses.
Frequently asked questions
- What size should I measure?
- For each end, measure the hose, pipe or port it joins with calipers. If that part slides into the fitting, measure its outside diameter and keep “Measure by: Inner diameter”. If the fitting slides into a hose, measure the hose’s inside diameter and switch to “Outer diameter”. Measure twice across the circle; flexible hose is rarely perfectly round.
- What should I print it in?
- PLA or PETG both work for dust collection at room temperature. Print in PETG or ASA if the air is warm or the part sits in the sun. Use 3–4 perimeters for an airtight wall; infill matters much less than wall count for ducts.
- What hardware do I need to buy?
- It depends on the options you choose. The “To buy” list in the designer shows exactly what your sizes need.
- Does it need supports?
- The export already places every component in its recommended print orientation. Keep supports off sleeves, sockets and any sliding or tight-fit surface so they stay smooth; if your slicer asks for supports, paint them only where an outside overhang needs them. Moving parts print separately; keep their sliding and turning faces free of supports and brim so they move freely.
More popular fittings
100 mm blast gateA 3D printable 100 mm sliding blast gate: housing and separate blade, held with standard bolts. Export 3MF, STL or STEP.
4 inch blast gateA 3D printable 4 inch blast gate with a separate sliding blade and bolt-on retainers. Free, adjustable, export 3MF, STL or STEP.
4 inch end capA 3D printable 4 inch end cap with adjustable bore, depth and fit clearance. Free, export 3MF, STL or STEP.
Sliding blast gateA housing and separate sliding blade, retained with standard bolts. Free 3D printable blast gate for any duct size.
Butterfly damperA separate rotating disc and shaft with a manual handle. Free 3D printable damper for duct and hose.
End capA removable cap with configurable bore, depth and end thickness. Free 3D printable, any size.