CELL 1 / reBot B601-RS FIT STUDY — 18 OCTOBER 2026

Result
The RS is a plausible pilot-cell candidate after rearranging the cell and changing the pickup/return strategy. It is not a drop-in replacement at the existing station positions. The detailed result applies to the WDG04 clamp geometry already in the Cell 1 model; it does not qualify the complete 01–16 family or production throughput.

The current 650 mm-radius layout passes 31 of 193 sampled position-and-orientation targets with the modeled RS and a 100 mm custom tool. It fails the complete cycle. The revised layout passes all 951 unique samples (0.01 legacy-phase-unit spacing, plus the endpoint). Minimum modeled joint-limit margin is 5.12 degrees, during the roll sequence. The viewer uses real forward kinematics; unreachable targets are not made reachable by stretching the arm.

Required changes shown in the model
1. Move pickup, deburr, kick, roll and output work points from 650 to 380 mm radius about the robot base: 270 mm (10.6 inches) inward.
2. Raise the nominal robot mounting face from 690 to 750 mm above the model floor and rotate the base 55 degrees about the vertical axis. This uses the manufacturer URDF coordinate convention; it is not a shop mounting-hole instruction.
3. Keep pickup/deburr/kick working height at 980 mm. Lower the roll work point from 980 to 880 mm. Its supports must follow the tooling, not preserve the old bench height.
4. Reverse the pickup and deburr approach orientations by 180 degrees. Present the blank at one known position with the correct face upward. The former upside-down pickup/flip path passes only 16 of 40 coarse samples; do not reuse it. Reshuffle or separately orient wrong-face blanks.
5. Fit a custom tool with 100 mm from link-6 flange origin to the material gripping point, including the assumed adapter, existing SMC-style gripper and narrow fingers. The stock supplied reBot gripper is not represented as the process tool. The actual bolt pattern, finger geometry, tool mass/center of gravity and measured TCP must be established before fabrication or robot programming.
6. Retain the newer 350 x 275 mm pneumatic tray concept. Shift its center from x=-780 to -510 mm. Lower its deck center from y=970.5 to 950.5 mm, add a raised locating nest for the 980 mm pickup and make a 60 mm access opening in the near rim. This clears the proposed gripper body. Fixed camera and lighting supports shift with the feeder; hoses and vibration motion are not part of the clearance proof.
7. Replace the separate 450 x 410 mm station bench tops in the close work zone with narrow 220 x 250 mm support envelopes, or a common frame designed to provide equivalent access. The existing wider tops are not assumed to fit unchanged. Fixture plates and purchased parts still need mounting details.
8. Turn the held part with the transfer to the output bin. The first version held its world orientation and would have required an approximately 350-degree wrist discontinuity across the joint limit.
9. After release, raise to a folded overhead posture, swing back around the front, then lower to pickup. The initial direct joint return intersected the kick/roll tooling. The replacement route reaches a maximum TCP height of about 1433 mm in this model and clears the screened fixtures. Check actual overhead obstructions and cable routing.

What was checked
- Official Seeed RS URDF joint origins, axes, joint bounds and visual meshes; six revolute joints, with the stock gripper removed from the tool model.
- Existing WDG04 stamped GLB and continuous material-coordinate kick/roll motion, including 217.5 degrees of wrap and 38 mm of withdrawal.
- Position residual under 0.5 mm and orientation residual under 0.25 degrees at each IK sample. Revised results are numerically far below those tolerances, but this is solver accuracy, not physical robot accuracy.
- Joint continuity and the return route, not merely one isolated pose per station.
- Robot visual-mesh vertices against oriented fixture box envelopes. Custom gripper, adapter, spacer, fingers and pads checked with oriented-box separating-axis overlap tests. The final proposed configuration has no detected overlaps at the sampled poses. Camera, light bars, updated tray, supports and local process fixtures are included.
- The rendering transform implementation was independently compared with the Python solver: maximum matrix-element discrepancy below 1e-6 (observed approximately 4.55e-13 before removal of duplicate time samples).
- The current public-model source snapshot uses the same station angles, 650 mm target radius, working heights, WDG04 mesh, forming-motion source and deburr catalog as the source used here. Its October 17 pneumatic tray geometry supersedes the earlier large tray and is used in the final fixture screen.

Limits that remain
This is sampled screening, not continuous collision certification. Mesh vertices can miss edge/face intersections; box envelopes simplify real tooling. Robot self-collision, cables/hoses, compliance, clearances under error, stopping behavior and the complete production environment were not qualified. The custom-tool and fixture dimensions are proposed geometry, not released manufacturing drawings.

Sizes 01–16 require their actual flat lengths, grip lands, kick geometry, mandrels and complete swept tool/part envelopes. The nominal range is 0.5-inch-wide bands, aluminum thicknesses 0.020/0.032/0.050 inches and steel thicknesses 0.020/0.032 inches in the prior local design basis. Tube diameter alone does not define the robot trajectory. We have not replaced missing family CAD with scaled copies of WDG04.

Eli accepts adding actuators/backstops/supports for process force. This study therefore does not reject the arm on forming-force grounds. It also does not verify force, grip retention, springback, deburring coverage or finished dimensions. Aluminum and steel share the geometric study only where their actual blank and tooling geometry match.

The legacy 9.5-second phase coordinate is used to identify existing process events, not as an RS time target. The viewer intentionally plays slowly. No speed, acceleration, duty-cycle or production-rate result follows from the reach test. The URDF velocity fields were not treated as validated operating speeds. Confirm firmware zeros/ranges and commissioning limits against the actual arm.

Practical next check
Build or measure the actual tool stack and record flange-to-grip TCP; load the largest and smallest actual blank/tooling envelopes; then perform slow dry-run pickup, kick approach, full roll and high return with the real hardware. This will resolve the remaining geometric questions before production programming. No force-measurement prerequisite has been imposed.

Sources and reproducibility
Official model: https://github.com/Seeed-Projects/reBot-DevArm/tree/main/Rebot_Arm_description/RS
Downloaded URDF: https://raw.githubusercontent.com/Seeed-Projects/reBot-DevArm/main/Rebot_Arm_description/RS/urdf/ReBot_Arm_RS.urdf
URDF SHA256: 3838ca8f9d586be22a89b33c7cbdd4abd43d4a92a2de377b294eef4c5bd7654d
robot.json records downloaded mesh SHA256 hashes. solutions.json records both configurations, sampled poses and joints. clearance.json records fixture solids and screen results. Source scripts are retained alongside these files. The original Cell 1 visualization remains available unchanged.