Sweep, revolve and extrude
Extrude pushes a profile in a straight line. Sweep drags it along a path. Revolve spins it around an axis. An organic bench and Fusion's trumpet sample show all three.
Three ways to turn a closed 2D profile into a solid. Extrude moves it perpendicular to the sketch. Sweep moves it along a path you draw. Revolve spins it around an axis. Most parts are some combination.
Sweep: an organic bench
The idea came from the blobby wooden seating at a bubble tea shop. The cross-section is a closed profile; the path is the curve of the bench.
- Sketch the profile with a fit-point spline: seat, backrest, round the bottom, then a straight line across the bottom so it sits flat. Trim to a closed shape.
- Press E to see what extrude gives you: the profile pushed straight back. No curve. That is the limit of extrude.
- New sketch on a plane perpendicular to the profile. Press P and Project the profile’s edge so you have a point that is truly on it. Start a fit-point spline from the middle of that projected line and draw the path.
- Sweep, solid, profile then path.
If Fusion says it cannot build the body, the path bends too tightly for the profile to follow without intersecting itself. Edit the path and ease the first bend. Orientation matters too: Perpendicular keeps the profile square to the path as it turns, which is what a bench wants; Parallel keeps it parallel to the original sketch and is more forgiving on tight curves.
Once it works, edit the path sketch and drag points. The sweep recomputes live, and you find out fast what curvature the profile will tolerate.
Sweep with a guide rail, extrude, revolve: the trumpet
Fusion’s Basic Training → 04 Modeling → Trumpet sample has every sketch ready. Save As first.
- Sweep, type Path + Guide Rail. Profile = the circle at the mouthpiece end. Path = the centreline; you may need two clicks to get the whole chain. Guide rail = the line tangent to the top of the circle. The guide rail is what lets the tube grow into the bell at the far end.
- Extrude the three valve circles 185 mm, operation Join. Long-press to pick a profile that is hard to click.
- Extrude the three inner rings -20 mm as a Cut for the valve caps.
- Revolve the mouthpiece profile around its centre axis, New Body. If the axis is not visible, turn on the sketch that holds it (Sketch 7 here). Sketches hide themselves after they have been used once.
