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[OpenArm Troubleshooting] End-Effector Z Check Fails After Table Move (Intermediate)

Z checks fail right after table remount? Distinguish workcell geometry shift from robot calibration drift with fixture-first tests.

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A practical OpenArm workcell problem appears after moving the table, fixture, or platform under the robot. The arm may still home correctly, but a simple Z-height check suddenly fails because the surrounding geometry changed while your assumptions did not.

How are you diagnosing OpenArm cases where the end-effector Z height check fails after a table move?

Please share how you distinguish a shifted environment from a robot-side calibration problem, which fixture or reference checks you trust most, and when you choose a fast workcell update versus a full recalibration.

If you reply, include one exact Z-check symptom and one exact workspace or fixture check that exposed the shift.

Related troubleshooting path: Base mount shift and stale calibration reference · Jog works but pick height is off

Module: OpenArm · Audience: builders-integrators · Type: question

Tags: openarm, z-height, table-move, workcell

Comment 1

Intermediate context: Our symptom was consistent: home passed, but the Z touch-off on the same fixture came in low by 1.4 mm after the table move. XY still looked reasonable, which made it easy to miss at first.

Comment 2

Intermediate context: What exposed it fast was a dial-indicator sweep on the fixture plate corners. We measured a clear tilt introduced during remount, so the issue was workspace geometry, not encoder drift.

Comment 3

Intermediate context: We allow partial recovery only if a 4-point plane fit leaves under 0.25 mm residual and the Z check passes three fixtures. Otherwise we redo full calibration and collision clearances before releasing the cell.

Comment 4

Intermediate context follow-up: Follow-up question: after table remount, what was your measured plane tilt and your final accepted Z residual threshold before releasing production?

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Quick FAQ

How do I separate table tilt from robot calibration drift?

Use a fixture plane fit across corners and center; consistent plane error usually indicates workspace shift.

python tools/fixture_plane_fit.py --fixture table_ref --points c1,c2,c3,center
python tools/z_touch_check.py --fixture all --trials 3
What should my release gate be?

Use residual + multi-fixture pass thresholds and confirm again at warm-state before release.

Can I copy these commands as-is?

Use them as a checklist template first. Confirm interface names, fixture IDs, and safety conditions in your own cell before execution.