Impeller (blower wheel)

A printable centrifugal blower wheel — straight, backward- or forward-curved blades on a bored hub.

A blower wheel is a backplate, a hub and a ring of blades. The blades are the part you cannot draw by hand, and they are the whole reason this is a generator rather than a few stacked primitives.

The blade is a curve, and two angles produce it. A blade's camber line is fixed by one thing — the angle it makes with the rim at each radius — and the curve is the integral of that angle along the radius. So you name where the blade meets the inlet circle and where it leaves the outlet, and the shape follows. Set both to 90° and you get a perfectly straight radial blade; that is not an approximation of straight, it falls out of the same formula. Below 90° the blade leans back against rotation; above 90° it leans forward.

Three families, or set the angles yourself. *Straight* blades run out from the centre and work whichever way the wheel turns — the simplest thing to print and the easiest to get right. *Backward-curved* blades lean away from the direction of rotation and are the efficient choice. *Forward-curved* blades lean into it: this is the squirrel-cage shape you find in furnace blowers and hair dryers, moving more air for its size while asking more of the motor. Choose Set the angles to drive the two numbers directly.

Get the rotation right. A curved blade only works one way round. Which direction the wheel turns is set from the inlet side, and it has to match the motor — putting a backward-curved wheel on backwards is the single most common mistake on a replacement, and it looks completely normal sitting still. Straight blades are the exception and do not care.

Watch the inlet gap. More blades guide the air better, right up until they crowd each other shut. Because a blade crosses the inlet circle obliquely it takes up more of that circle than its own thickness, and the inlet circle is the shortest one — so blades run out of room *there* first, while the outside of the wheel still looks roomy. Once the gap closes the blades fuse into a solid ring with no way in, and the part still looks like a wheel. The Inlet gap row is the only thing that will tell you: it turns orange when the blades are closer together than they are thick, and red when the inlet has actually closed.

Fitting the shaft. Shaft diameter is the shaft, not the hole — the bore is cut to that plus whatever the fit adds. This wheel is meant to grip rather than turn, so it runs tighter than the moving parts elsewhere in the catalogue; loosen it if it will not go on, tighten it if it slips. For a D-shaped motor shaft set Shaft flat to the depth of the flat, measured in from the round, and the bore is cut to match so the wheel cannot spin on the shaft.

Print it as it arrives. The wheel is emitted backplate-down, which is how it has to print: every blade is then a vertical wall standing on the plate, needing no support, and the layers run across the load that tries to peel a blade off its root. Do not stand it up. The one overhang in the whole part is the optional shroud ring, which caps the blade tips and stiffens a tall wheel — its first layer has to bridge from blade to blade, and the Shroud bridges row reports that span so you can shorten it with more blades if it is getting long.

What this does not tell you. It makes no claim about how much air the wheel moves — no airflow, no pressure, no efficiency, no noise figure. Those depend on the housing, its cutoff, the motor and the tip clearance, none of which this part knows about, and we have no test rig to measure them on. What it does claim is geometric and checkable: the blade meets each circle at the angle you asked for, the passage between blades is open, the wheel is one watertight solid, and the bore fits the shaft you named. Run Print check over the result before you commit filament to it.

1. Open the Generate panel from the left sidebar and choose Impeller (under Fans & airflow).
2. The wheel drops in as one printable body. The parameters open in the Properties panel.
3. Pick a blade family — or Set the angles to drive the inlet and outlet angles directly.
4. Set Turns to match your motor. A curved blade only works one way round.
5. Set the wheel and inlet diameters, the blade height and the blade count, watching the Inlet gap row.
6. Enter your Shaft diameter (the shaft, not the hole), and a Shaft flat if it is a D-shaft.
7. Print it backplate-down, exactly as it arrives.