Fan frame and guard

A printable axial fan frame on a standard hole pattern, with an optional guard and motor boss.

A fan frame is the square an axial rotor turns inside: the housing that bolts to a panel, the guard that keeps fingers out of it, and — if you want one — the mount the motor sits on. It is the third piece of the set, after the axial fan rotor and the impeller.

Name the size and it bolts on. The 40, 60, 80 and 120 mm frames each carry their own square, mounting pitch and screw size, and those come from the same table the panel-cutout shapes in the library are built from. So a frame you generate and the hole you cut for it agree by construction, rather than because two people typed 71.5 on different days. The mounting pitch and screw size are to spec — the 80 mm row from ARCTIC's published drawing — and the panel will not let you overwrite them on a named size, because that is the whole value of naming one. Choose Custom for a size the table does not list, and all three become yours.

The bore is the one number you set yourself. It is the round opening the rotor turns in, so make it your rotor's tip diameter plus a little running clearance. The Takes a rotor up to row does that arithmetic backwards for you: it reports the largest rotor the bore will accept, and that figure goes straight into the axial fan generator's Tip diameter. Between the two, the pair fits without you guessing a clearance.

Struts and rings make the guard. Struts are bars running out from the middle; rings are concentric circles carried by them. Zero of both leaves the bore clear, which is what you want for a plain shroud or a duct flange. The Largest opening row reports the biggest thing that still passes through — a distance rather than a percentage, because a percentage reads like an airflow number and the size of the gap is the question a finger actually asks.

Rings and the boss cannot float. Both are held by the struts, so asking for either with no struts would give you a part that comes off the plate in pieces. Rather than silently dropping them, the strut count is raised to two and the panel shows the number it raised it to — a control that quietly did nothing would be worse than one that visibly moved.

Switch on the motor boss and the struts carry a cylinder in the middle for a small motor, bored through for its body or its wires. Frame, guard and mount then come off the plate as a single piece.

It prints face down, with no support anywhere. The guard sits in the first few millimetres, laid flat on the plate, and the bore above it is a vertical wall. That is why the guard is on the underside rather than at the outlet end, which would look tidier and print worse — if you want it the other way round, turn the printed part over rather than the model.

What it does not tell you. Nothing about airflow, pressure or noise. A frame changes all three and this one cannot measure any of them. What it does claim is checkable: the square is the size you named, the holes are on the published pitch and clear of both the bore and the edge, the bore is round and empty, and the largest opening in the guard is measured rather than estimated. Run Print check over the result before committing filament.

1. Open the Generate panel from the left sidebar and choose Fan frame (under Fans & airflow).
2. The frame drops in as one printable body. The parameters open in the Properties panel.
3. Pick the Frame size — it carries the square, the hole pitch and the screw size for you.
4. Set the Bore to your rotor tip diameter plus a little clearance, and read off what rotor it takes.
5. Add Struts and Rings for a finger guard, watching the largest-opening row.
6. Turn on the Motor boss if the frame has to carry a motor, and set its hole.
7. Print it face down, exactly as it arrives — nothing in it needs support.