The case of the unstable label
“My labels are wandering,” said Kelley.
“Well, that’s no good; they need to stay at home where you can keep an eye on them,” I quipped.
Kelley didn’t appreciate the humor but asked me to come take a look.
The labeler detected the gap between labels with a photo eye to position the label at the edge of the peeler plate. This label was transparent, and the eye was set to detect a label graphic instead.
Sometimes the label feed would stop short. Other times it ran over. Labels must always stop with the edge of the peeler plate in the middle of the gap to avoid application problems.
“Fiddlesticks on wandering labels, ” I roared. “You are triggering off of a circular graphic. It is opaque enough to give a good signal, so no problem there. If the label moves sideways even a little bit, the edge of the graphic, relative to the leading edge of the label changes. That’s what’s giving you an inconsistent stop position.
“You need to do two things to fix this problem,” I continued. “First, you need to go through the labeler fixing any loose or non-perpendicular guide rollers. This will stop your web from wandering side to side. Then you need the proper sensor. Get rid of the photo eye; it was never meant to work with a transparent label. A capacitance sensor will sense the edge of the label and stop precisely every time.”
What you see is what you get. If you can’t see the label, you can’t control it.