The printer skips labels, feeds several blank ones, stops halfway, or shows an error like gap not found, top of form or out of stock. It can't find the edge of each label. Usually the sensor is set for the wrong label type, it's in the wrong place or dirty, or the printer needs to be calibrated for your labels.
⚡ The short version
- Re-load the labels straight, under the guides, and close the head firmly.
- Check the sensor type matches your labels: gap, black mark or continuous.
- Run the printer's calibration (steps for Zebra, Honeywell/Datamax and Sato below).
- ⚠ Before cleaning: turn the printer off and unplug it, and let the printhead cool, because it gets hot during printing. Use only a printhead cleaning pen, or a lint-free swab lightly dampened with isopropyl alcohol if your printer's manual allows it. Never use anything sharp or metal on the printhead. Touch the printer's metal frame first to discharge static.
Clean the sensor if it still can't find the labels.
Zebra ZD421 and ZD621 (SmartCal)
Load the labels and close the cover
Load the labels (and the ribbon, if you use one) and close the top cover. Turn the printer on and wait for the STATUS light to turn solid green.
Run SmartCal
Press and hold PAUSE and CANCEL together for two seconds, then let go. The printer feeds and measures a few labels. When it's done, the STATUS light turns solid green again. ZD621 printers with a colour touch display have the same buttons, so this works the same way. They also have a step-by-step manual calibration wizard at Print → Sensors → Manual Calibration.
Calibrate again when you change labels
Zebra says you don't need to calibrate again for the same kind of labels. If you load labels of a different size, type, maker or batch, run SmartCal again.
Honeywell / Datamax-O'Neil (Class series, such as H-Class and M-Class)
Honeywell's support pages give slightly different button timings for different models. Follow your model's operator manual if it differs.
Check the sensor type and position
Go to MENU → MEDIA SETTINGS → SENSOR TYPE and make sure it matches your labels (gap is the default on the H-Class). Raise the printhead, line the media sensor up with your labels, then lower the printhead and lock the latch fully. Press FEED a few times to see if the error clears.
Run a quick calibration
With labels loaded and the printer on and idle, press and hold FEED until one full label feeds out, then let go. The display should show CALIBRATION COMPLETED, then READY. If it shows CANNOT CALIBRATE, hold FEED again until two labels have fed. (On some models the message is CALIBRATION FAILED, and models without a display flash a light instead.) If your model's operator manual says something different, follow the manual.
Empty calibration (for out-of-stock detection)
Honeywell's manuals say empty calibration sets the media sensor to detect an out-of-stock condition. Make sure the printer is on and idle (not offline), with the labels removed. Press and hold PAUSE and FEED together. The M-Class Mark II manual says to hold them for a few seconds. On the H-Class it's a long press, because a short press of PAUSE and FEED prints a test label instead. Don't hold these buttons while switching the printer on: the H-Class manual lists PAUSE + FEED at power-up as a reset.
Still getting top-of-form faults?
Honeywell suggests checking MENU → MEDIA SETTINGS → MAXIMUM LABEL LENGTH. Honeywell's H-Class manual says it should be 2.5 to 3 times your label length. Check your model's manual for the right value. Some printers only show all the options after you set MENU → SYSTEM SETTINGS → MENU MODE to ADVANCED MENU. You can also run a full calibration from MENU → MEDIA SETTINGS → SENSOR CALIBRATION → PERFORM CALIBRATION.
Sato CL4NX Plus (error 1028, Gap Not Found)
Clear the error and re-load the labels
Sato says to press the OFFLINE button or open and close the print head to clear error 1028. The causes it lists are labels wandering off line, a label stuck on the media sensor, the wrong sensor type, or a wrong sensor level. Re-load the labels straight and clean the sensor if a label is stuck to it.
Check the sensor type
Sensor Type is in the Printing menu. The factory setting is Gap. Set it to match your labels.
Run Auto-calibration
Go to Settings → Printing → Advanced → Calibrate → Auto-calibration. Sato's steps: unlock the print head, take a label off the backing and pass the backing only under the media sensor guide, then lock the print head. Use the ▲/▼ arrows to choose Gap, I-Mark or Gap + I-Mark, press Enter, then confirm on screen to start. Afterwards go Offline and press the FEED soft button to check the labels feed correctly.
Sato says Auto-calibration isn't available if the optional linerless cutter kit is installed. If labels still don't feed correctly, contact your Sato reseller or Sato support.
Sources
- Zebra ZD421/ZD621 User Guide: Running a SmartCal Media Calibration
- Zebra ZD421/ZD621 User Guide: Recovering from a Media-Out Condition
- Honeywell: How to Fix Top of Form Errors
- Honeywell: How to manually calibrate stock on the Datamax H-Class printer
- Honeywell: How to calibrate media on Datamax-O'Neil stationary printers
- Honeywell H-Class Operator's Manual (PDF, distributor copy)
- Honeywell M-Class Mark II Operator's Manual (PDF, distributor copy)
- Sato CL4NX Plus manual: Error Message 1028 (Gap Not Found)
- Sato CL4NX Plus manual: Auto-calibration
- SATO CL4NX Plus/CL6NX Plus Operator Manual v2 (PDF): operator panel buttons
- Honeywell I-Class Mark II Operator's Manual (PDF, distributor copy)
- Sato CL4NX Plus manual: Cleaning Using the Cleaning Kit