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Every print job ejects one good label — and one blank behind it. Over a shift that is a full roll wasted. The habit is to recalibrate and hope; the faster path is to read two numbers in the file first, because two of the three causes live in the ZPL.
ZPL measures length in dots. If the file says ^LL1218 — six
inches at 203 DPI — and the physical label is four inches, the printer
dutifully renders a six-inch canvas and feeds media until it has covered it:
your four-inch label plus most of the next one, which comes out blank (or
worse, carries the bottom of the layout). The check is one division:
^LL ÷ your printer's DPI must equal the physical label length.
A file converted from a different DPI without rescaling fails this check by
exactly 1.5× — the same mismatch that clips labels horizontally.
^PQ sets the copy count. A leftover ^PQ2 from a
template prints every label twice — and when the duplicate's data fields are
empty (a serial that incremented away, a variable that only fills once), the
second copy looks like a "blank". The tell: the extra label is not fully
blank under strong light, or appears only for certain jobs.
Only after the file checks out is it a media-tracking problem: the sensor
misreading the gap between labels, the wrong tracking mode for the stock
(gapped vs. continuous vs. black-mark — selected by ^MN or the
printer menu), or a sensor that needs recalibrating after a media change.
That is physical: run the printer's calibration routine and confirm the mode
matches the stock. No file edit fixes a sensor that has never seen your
labels.
Divide ^LL by your DPI — wrong length, cause 1. Search
for ^PQ — copies >1, cause 2. Both clean → calibrate.
A preview draws exactly the canvas the file declares, so an oversized
^LL is visible on screen as a label taller than your stock; what
no preview can see is your physical roll — the file-vs-media comparison is
the one step that stays yours.
Check the file first: a ^LL longer than the physical label makes the printer feed into the next label to cover the declared canvas, and an unintended ^PQ prints near-blank duplicates. Only when both are clean is it media tracking — run the printer's calibration.
Divide ^LL by the printer's DPI: ^LL1218 at 203 DPI is six inches. If your labels are four inches, the file overruns them by definition. A file converted from another DPI without rescaling misses by exactly 1.5x.
Only when the file is right. Calibration teaches the sensor where labels start and end; it does not shrink an oversized ^LL and does not remove a ^PQ. Fix the file first, then calibrate if the symptom remains.
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