METHEUS · ENGINEERING REPORT · v1.3

Extended-finger load review

Actual linear-static FEM of the two 50 mm exposed fingers, with a separate rigid-body planar drive calculation. The final CAD geometry is preserved in both finger analyses.

21.479 MPaRight finger · raw peak, 0.8 mm mesh

19.593 MPaLeft finger · raw peak, 0.8 mm mesh

0.05197 mmRight finger · maximum displacement

0.03931 mmLeft finger · maximum displacement

Peak stress is not converged. The last mesh refinement changes displacement by 0.11–0.13%, but raises the raw stress peaks by 10.45–15.74% at sharp foot-to-shank corners. These results do not establish a validated safety factor or a whole-gripper pass.

Actual FreeCAD right-finger von Mises result on undeformed geometry — Actual FreeCAD result display: right finger, 0.8 mm mesh, undeformed geometry. Raw von Mises range: 0.054–21.479 MPa. This captured native view has no numeric color bar.

Load case and model

Condition	Applied value
Material	Aluminium 7075-T6; E = 71,700 MPa; Poisson ratio 0.33; assigned yield 503 MPa
Support	Entire bottom mounting-foot face fixed in all three translations
Normal load	25 N per finger; +X on the right, −X on the left
Tangential load	7.405 N in −Y in each separate case
Assumption	Entire 0.5 kg × (9.81 + 5 m/s²) assigned to each individual finger
Load application	Forces distributed on the aluminium tip face at Z = 82 mm
Engine	Installed METHEUS FEM service · FreeCAD 1.1.1 / CalculiX 2.22

Mesh refinement

Finger	Maximum element size	Nodes	Raw peak stress	Maximum displacement
R	1.8 mm	22,881	17.132 MPa	0.051740 mm
R	1.2 mm	45,891	18.558 MPa	0.051913 mm
R	0.8 mm	105,369	21.479 MPa	0.051972 mm
L	1.8 mm	21,751	16.592 MPa	0.039111 mm
L	1.2 mm	42,780	17.739 MPa	0.039257 mm
L	0.8 mm	95,833	19.593 MPa	0.039307 mm

Actual solver result comparison over three mesh sizes for both fingers — Comparison uses all six actual solver results. No clipped or filtered stress replaces the raw maximum.

The material values are analysis-card assumptions, not a material certificate. Production fillets, local stress convergence, mounting-foot screws, carrier flexibility, pad bond and contact, eccentric torsion, fatigue and physical payload retention remain to be checked.

Separate planar drive review

Calculation	Result
Normal-load pair peak	1.913390 N·m
Combined conservative sample peak	1.955724 N·m
Motor demand at 85% assumed efficiency	2.300852 N·m
Selected motor rated torque	2.5 N·m

Rigid-body virtual work uses the original 72 motion samples, 25 N normal load per jaw and 7.405 N total tangential load. Absolute component contributions are combined at each sample; separate component maxima are not simply added. The change in finger Z reach does not double the planar rotary torque. Inertia, friction, motor thermal duty and out-of-plane assembly strength are outside this calculation.

Historical plate analysis and source checks

The v1.2 three-plate planar MFBD result is retained as historical evidence only. It is not a fresh validation of the longer fingers, revised adapter or full assembly. The actual finger solids were compared against the final native CAD in local coordinates: both Boolean differences are zero for each side. Distributed load sums and fixed/loaded face planes were independently checked in all six solver input decks.

Independent review record · Recorded prompts and subsequent review