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Homing & Fiducial

Establish a connection with the top camera, then set up the datum board. The center dot on the datum board is the homing fiducial — the key calibration point that fine-tunes the machine's XY position to compensate for minor limit-switch variation.

The homing fiducial is the 1mm dot in the center of the Opulo logo on the datum board.

Configuring the Top Camera​

  1. Navigate to Machine Setup → Heads → ReferenceHead H1 → Cameras → OpenPnpCaptureCamera Top → Device Settings tab.
  2. Select LumenPnP Top from the Device dropdown.
  3. Set Resolution/Format to 1280x720, 10fps — a low frame rate is crucial to avoid bandwidth issues.
  4. Click Apply, then File → Save Configuration.

Preparing for Homing​

  • Machine Setup → Heads → ReferenceHead H1 — Homing Method set to None
  • Machine Setup → Nozzle Tips → ReferenceNozzleTip N045 → Auto Recalibration: Manual
  • Machine Setup → Nozzle Tips → ReferenceNozzleTip N24 → Auto Recalibration: Manual
Critical: level the nozzles before homing — now and every time. OpenPnP does not remember previous nozzle positions. If nozzles are not level before homing, they may collide with the machine, causing misalignment or serious hardware damage.

Click Home to perform a rough homing sequence. The nozzles move to X/Y/Z zero (front-left corner) and park.

Setting the Homing Fiducial Location​

  1. Navigate to Machine Setup → Heads → ReferenceHead H1.
  2. In the Configuration tab, change Homing Method to ResetToFiducialLocation.
  3. Click Apply and save.
Do NOT click homing again until you have fine-tuned the homing fiducial location in the next section.
  1. Click Position Camera Over Location — the top camera moves above the datum board.
  2. Ensure LED lights are on (Machine Controls → Actuators → LED → On).
  3. In the top camera Device Settings, toggle Auto off for Exposure to enter manual mode.
  4. Use the jog controls to center the reticle over the homing fiducial (center of the Opulo logo).
  5. In Machine Setup → Heads → ReferenceHead H1, click Capture Camera Location for the Homing Fiducial.
  6. In the Calibration Rig section, click Capture Camera Location next to Primary Fiducial.
  7. Click Apply and save.

Fine-tune Camera Exposure​

  1. In the top camera Device Settings, right-click the feed and select Show Image Info to enable the brightness histogram.
  2. Adjust the exposure slider.
Keep all other camera settings at default and only adjust the exposure. Aim for a sharp peak on the right and a larger cluster to the left. The histogram is only an example — focus on a distinct right peak and a noticeable left cluster, not an exact match.
Not seeing anything in the top camera feed? Ensure the lens cap is removed.

Record your exposure value in a text file — OpenPnP may not retain camera settings after restart. Each boot, toggle Auto Exposure on then off, then type your recorded value. Turn off the histogram when done and save.

Test Fiducial Homing​

Click Home and watch the machine home via limit switches, then move the top camera over the homing fiducial. When scanning, the fiducial will have a red-colored hue.

If you get the error FIDUCIAL-HOME no matches found, OpenPnP can't find the fiducial — adjust the Homing Fiducial Pipeline.
Next: Continue to the MM/Pixel Calibration.