Calibrate the Zebra ZD421: SmartCal and manual calibration

Calibration tells the ZD421 how long your labels are and where each one starts. Without it, the printer may skip labels, print across the gaps or stop with a media-out light although labels are loaded. Most of the time the automatic SmartCal is enough; for difficult labels there is a manual calibration.

When to calibrate

• When you set up a new printer.
• When you change to a different label type, size or supplier.
• After a factory reset.
• When labels skip, print across the gaps or the printer reports media out with labels loaded.

A new roll of the same labels from the same batch needs no calibration. Press FEED once or twice after loading it, and the printer lines up the labels by itself.

Know your labels

On a ZD421t or ZD421c, load the ribbon before you calibrate.

Set the movable sensor

The movable media sensor sits under the labels. It slides sideways along an alignment key, and an alignment arrow shows its position.

1. Slide the release latches towards the front and open the cover.
2. Flip the labels up so you can see the sensor and the back of the labels.
3. Gap labels and continuous media: set the arrow to the default position marked on the alignment key. Gap sensing only works while the arrow points to a position on the key.
4. Black mark, notched or punched labels: move the arrow to the middle of the mark or notch. Keep it as far from the label edge as you can, while the mark still covers the whole sensor window.
5. Lower the labels and close the cover until the latches click.

Run SmartCal

1. Switch the printer on and wait until the STATUS light is steady green.
2. Press and hold PAUSE + CANCEL for 2 seconds, then let go.
3. The printer feeds and measures a few labels. It sets the sensor levels, works out the label type and measures the length.
4. When STATUS is steady green again, calibration is finished.

Calibrate manually if SmartCal fails

Use manual calibration when SmartCal doesn't recognise your labels, for example with pre-printed liners or unusual black marks. The printer measures the bare liner first and then a label.

1. With labels loaded and the printer on, hold PAUSE for 2 seconds. All lights flash, then STATUS stays steady amber: the printer is in Advanced Mode with Manual Media Calibration selected.
2. Press PAUSE once to start. The SUPPLIES light flashes amber, then the PAUSE light flashes.
3. Open the printer and check the sensor position (see above). On pre-printed media, place the sensor where there is little printing on the label front or liner back.
4. Peel about 80 mm of labels off the liner.
5. Lay the bare liner over the platen roller (the drive roller), with the front edge of the first remaining label under the media guides.
6. Close the printer and press PAUSE once. The SUPPLIES light flashes while the printer measures the liner; when it is done, the PAUSE light flashes.
7. Open the printer and move the labels so that a label sits directly over the movable sensor. Close the printer.
8. Press PAUSE once. The printer feeds and measures several labels. When STATUS is steady green, calibration is complete.

If the printer does not return to steady green, move the sensor slightly and repeat. To leave Advanced Mode without calibrating, press CANCEL. Zebra's video shows a ZD411; the steps are the same on the ZD421.

Video: Zebra Technologies

Check the result

Press FEED once. The printer should advance exactly one label. Then print a test label from your software and check that it lands on the label, not across the gap. In the driver, the label size must match the labels you have loaded.

Symptoms and fixes

For the meaning of each light, see ZD421 lights and errors. New to the printer? Start with the ZD421 setup guide.