learndesign.tech Search

Modelling from sketches, the rocker arm

· Fox Bright

Fusion's Model from Sketch sample, step by step. Two-sided extrude to an object, symmetric extrude from the mid-plane, projecting a circle onto a face, mirroring a feature, and a fillet.

A finished mountain-bike rocker arm bracket in Fusion with a bore through one end and a counterbore mirrored on both sides.

This is a mountain bike rocker arm, a bracket that gives the rear suspension its pivot. Fusion provides the sketches; you add the features. It is a good exercise in reading instructions one step at a time and in the difference between the ways an extrude can end.

Open and save

Data panel → home → Samples → Basic Training → 04 Modeling → 04 Model from Sketch. Save As somewhere you own; the sample folder is read-only.

The body: a two-sided extrude to an object

Select the main profile, everything except the innermost circles. Extrude. Direction: Two Sides. For each side, extent To Object, and click the sketch line that marks where that side should stop. No numbers typed; the sketch already knows.

Fusion extrude dialog with direction Two Sides and the rocker arm profile highlighted in blue
Two-sided extrude with both extents set To Object, ending on the two sketch lines.

The rear boss: symmetric from the mid-plane

Select the larger of the two circular profiles at the end, with its centre circle, and extrude Symmetric, 20 mm total, Join. I model symmetric parts from their mid-plane whenever I can; both sides stay equal and you only manage one number.

The bore: edit the sketch, project, cut

  1. Right-click Sketch1, Edit Sketch. Add a 10 mm circle at the centre (C, snap, type 10). Finish.
  2. Press P for Project, pick the outer face of the boss as the sketch plane, then click the new circle. It appears on the face in purple.
  3. Extrude that circle as a Cut, extent To Object, click the far face. Straight through.

The point of projecting rather than just sketching a new circle: it stays tied to the original sketch. Change the 10 there and the bore follows.

The counterbore: same trick, then mirror

Edit Sketch1 again, add a 24 mm circle at the other end. Project it onto that outer face. Extrude the ring between the projected circle and the smaller one as a cut, -10 mm.

Fusion extrude dialog set to cut with distance -10 mm on a red highlighted ring profile
The counterbore cut, 10 mm deep, from the projected circle.

Now Mirror (S, type mirror). Object type Features, pick that extrude-cut from the timeline, mirror plane = the origin plane through the middle of the part. Turn the Origin folder on if you cannot see it. Both sides now match, and they will keep matching.

Finish

Extrude-cut with the bottom rectangle sketch. Select the two inside corner edges, press Q, and fillet at 5 mm.

Fusion fillet dialog with two inside edges of the rocker arm selected
A 5 mm fillet on the inside corners finishes the part.