Zebra ZD421T label printer

Where art paper or Yupo labels must be printed with a ribbon, the Zebra 4-inch desktop ZD421T fits, and the same unit also prints direct thermal paper labels without a ribbon. It is a ZPL printer, so GoodLabel Designer does not hand print jobs to the driver but sends them directly as ZPL commands (RAW).

Differences between the 203 dpi and 300 dpi variants

Where many shipping or box labels are printed at once, the 203 dpi variant, which goes up to 152 mm per second, is faster. To fit small text and QR codes together on a small label such as 30×10 mm, the 300 dpi variant, with dense 0.085 mm dots, fits.

The 203 dpi listing also offers the ZD230TA (203 dpi), a separate USB-only entry-level model. In the Designer model list, the ZD230 is a ZPL printer with only 203 dpi.

Steps to connect GoodLabel Designer

The Designer model list has only the single line ZD421, without the T. Thermal transfer and direct thermal are distinguished not by the model but by the print method in Printer settings.

• First install the Zebra universal driver v10 from Downloads to register the ZD421T as a Windows printer.
• In the Printer field of the Designer's Printer settings window, select that printer, choose ZD421 in the Printer model field, and in Printer resolution (DPI) choose 203 DPI or 300 DPI to match your unit. If the printer name includes ZD421 and a resolution such as 203dpi, the model and resolution are set automatically.
• In Printer settings, enter the label width and height in mm; then, if a ribbon is loaded, set the print method to Thermal transfer, and if only direct thermal paper is loaded, set it to Direct thermal. The Designer sends this choice with the job as the ^MTT or ^MTD command.
• The media type is Gap labels (^MNY) for rolls with space between labels, Black mark (^MNM) for rolls with black bars printed on the back, and Continuous media (^MNN) for continuous rolls. The Gap length field in Printer settings is for TSPL and EZPL printers, so it is not included in the ZPL commands sent to the ZD421T, and the label gap is picked up by the auto detect below.
• After changing rolls, run Auto detect once in the Troubleshoot window. For the ZD421T, the ~JC command is sent to set the sensor reference to the new media and measure the label length and gap again.
• If a test print is faint, raise the density in the Print window. The density range for ZPL printers is 0–30, and the default is 21.

For black mark rolls, move the arrow of the movable sensor inside the unit to the center of the black mark, then run auto detect. If "Print as image" is checked in Print options, the driver's media settings apply instead of the options above. Screen-by-screen explanations are in the Printing chapter of the guide.

Ribbons and labels for the ZD421T

It takes ribbon rolls of 300 m (core 25.4 mm, OD 66 mm) and 74 m (core 12.7 mm, OD 34 mm), with a width range of 33.8–109.2 mm. Non-Zebra 300 m ribbons are mounted on the 300 m ribbon adapter packed in the thermal transfer model's box; the core must be 25.4 mm ID cardboard and the roll OD 66 mm or less.

Choosing a ribbon wider than the media reduces head wear. The GoodLabel wax ribbon 300M variants cover 40–110 mm in 10 mm steps, so choose the width one step wider than the roll width including the liner.

Media fits at 15–112 mm width, 0.08–0.1905 mm thickness and up to 127 mm roll OD. When you switch to GoodLabel thermal roll labels, which are used without a ribbon, remove the ribbon and change the Designer print method back to Direct thermal.

Where to check the resolution setting

The status bar at the very bottom of the Designer screen always shows the driver, printer model (resolution) and print options. If the resolution differs from your unit, print quality drops, so check this bar first when the first label looks wrong.

A .glb file stores the printer and DPI at the time it was saved, so when you open a file made with 203 dpi settings, the resolution also returns to 203. To use it on the 300 dpi variant, open the file and change to 300 DPI in Printer settings; the barcode bar width and QR module size are then recalculated for the new resolution.