What a web-width stitch is, and when the seams hide defects
A web-width stitch joins several cameras into one full width. The seam is the overlap. If the overlap is narrower than the defect, the defect sits where neither camera owns it. Name one camera to alarm inside the overlap, or you miss it or count it twice.
A web-width stitch is several cameras each looking at one section, then joined into a full width. The seam is the overlapping strip. If the overlap is narrower than the defect you must catch, the defect falls where neither side owns it. Inside the overlap one camera must be named to alarm. Otherwise the defect is missed, or the same defect alarms twice.
Two errors on the seam
If each camera throws away its own edge as unreliable, both throw it away and a strip is missing in the middle. If both alarm, one dirt spot becomes two alarms, and the count and the reject both go wrong. So the overlap must be wider than the defect, and the software must say which camera owns that strip. The other camera is only for alignment and must not alarm again.
When the web wanders side to side, the seam moves. Widen the overlap by the largest wander. Do not leave it at the one pixel that lined up while the web was stopped.
Setup
| Case | Result | Change |
|---|---|---|
| Overlap smaller than the defect | A miss | Widen the overlap, or give each camera less width |
| Both cameras alarm | Double count | Name one camera as master |
| The web can wander | The seam leaves the overlap | Widen by the wander |
Check at a job change
- Run a defect sample placed exactly on the seam.
- Confirm one alarm, not zero and not two.
- Let the web wander inside the allowed range and try again.
