All five are read in one state — gripper fully closed, blades installed — and together they fix everything still open on the gripper: how far apart the blades sit, which way they converge, and whether the two protrusion faces can meet as faces rather than as a line.
Two distances only fix a translation. The two mounting patterns can also be rotated relative to each other, and the URDF says they are: at full closure the two jaw axes sit 10.79° apart. Two distances plus one angle pin the relative pose completely — and the inner-bolt offset as components rather than a straight-line distance, because when two lines are not parallel a single distance between them is ambiguous.
| Point | Where exactly |
|---|---|
| P1 | Left blade — outermost corner of the mounting foot's bottom face |
| P4 | Right blade — outermost corner of the mounting foot's bottom face |
| L_out | Left base — centre of the bolt further from the centreline |
| L_in | Left base — centre of the bolt nearer the centreline |
| R_in | Right base — centre of the bolt nearer the centreline |
| R_out | Right base — centre of the bolt further from the centreline |
| TL / TR | The two blade tips |
| Read | What it settles | |
|---|---|---|
| A | P1 → P4, horizontal | Where the feet sit — with B, gives the bolt-to-foot-edge offset |
| B | L_out → R_out, horizontal | Where the bolts sit. (A − B) / 2 compares against the CAD's 5.004 mm |
| C | L_in → R_in, as Δx and Δy | Pins the two bolt patterns' relative position exactly, independent of A and B |
| T | TL → TR, horizontal | With A, gives the convergence: atan((A − T) / 2 / 89.4) |
| θ | Angle where the two bolt lines cross, extended | The mounting-plane angle. Also say which side they converge toward — tips or base |
If a pair of points is not level, take the horizontal component — square across, not diagonally. 89.4 mm is the foot-bottom to tip distance from the CAD (z −33.985 to 55.44).
| Reading | Predicted | Where the prediction comes from |
|---|---|---|
| (A − B) / 2 | 5.004 mm | Measured off Blade_v4_final.stl: outer hole to foot outer edge. A mismatch is HOLE_DX |
| Each bolt pair spacing | 10.0 mm | The operator's caliper reading on the real hardware — a cross-check that the right points are being used |
| θ | ≈ 10.79° | From the URDF joint at full closure. This is the real test — if the measurement lands near it, the kinematics can be trusted for everything downstream |
| A − T | — open | No prediction. This is the one that resolves whether the mating face needs flattening or leaving alone |
The blade's mating face currently sits 5.93° off the blade's own axis, following the inner rail. Each jaw sits 5.40° off the mirror plane. If those two tilts oppose each other they nearly cancel (−0.53°) and the face is already almost parallel — flattening it would make things worse. If they add, the real error is 11.33°, twice what flattening corrects.
A flattened variant is already built and passes every mesh check — mating face
0.036° off parallel, down from 5.93°, with the tip still 0.99 mm sharp. It carries a
single switch, FLATTEN, that can be set to 0 to fall back or negated to reverse
the correction. θ decides which.
With all five in hand: HOLE_DX is computed, the FLATTEN sign is
settled, and the inward hook is already done. All three go into the source together, the
three build steps re-run, check_mesh and check_ribs confirm it, and
the closed top view gets redrawn with a correctly aligned pair — so the tip contact can be
judged on an assembly that actually lines up.