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SO-101 gripper top view simulated from the URDF 2026-08-21

Jaw Closure

What the gripper actually looks like from above as it closes, computed from the robot's own joint definition rather than eyeballed. This is the frame any tip-geometry decision has to be judged in.

The kinematics are not a guess

Taken straight from xlerobot.urdf, joint Jaw: revolute about Z, origin (−20.2, −24.4, 0) mm, rpy (3.1416, 0, 3.33), limits 0 → 1.70 rad. Zero is fully closed; 1.70 rad = 97.4° is fully open. Because the axis is Z, the whole opening motion happens in the XY plane — so a top view is the true view of this mechanism, not a projection that loses something.

The outlines are real mesh cross-sections: Fixed_Jaw.stl and Moving_Jaw.stl sliced at z=0, with the moving one carried through the joint transform at each angle.

Closed
0°
joint lower limit
Open
97.4°
1.70 rad upper limit
Tip gap closed
7.25 mm
between the two tip reference points
Pivot
−20.2, −24.4
mm, in the fixed-jaw frame

01 — The mechanism

Drag the slider to close and open it

Blue is the fixed jaw, orange the moving one. The dashed line is the distance between the two tip reference points the URDF defines.

Top view · millimetres joint angle 0° — fully closed
pivot 7.25 mm
!

What this view cannot answer yet

This is the stock jaw pair. Overlaying the new long Fin-Ray blade needs one more transform — where the blade's mounting foot sits on the jaw — and that cannot be pulled from the files with confidence: the blade STL carries mounting holes, but the jaw meshes in the URDF are the compliant jaws with the fin already integrated, not a bare mount with a hole pattern to match against.

So the question "do the two tip protrusions meet cleanly at full closure" is still open, and it is the same open item as HOLE_DX — the lateral hole shift requirement 2B asks for and nobody has measured. Requirement 2B records that with the current holes the two long fingers can cross rather than close through part of the motion.