Zebra ZD421d direct thermal desktop printer

Name: Zebra ZD421
Brand: Zebra

Zebra ZD421

The ZD421d is a current 4-inch direct thermal printer that prints without a ribbon, taking 15-108 mm media, with speed set in 5 steps from 51 to 152 mm per second. Start with USB 2.0 only, and when you need LAN or Wi-Fi, buy a module and fit it into the rear or bottom cover.

Max print width

104 mm (203 dpi)

Media width

15-108 mm (ZD421d)

Drivers and manuals4 files

ZD421 specifications

Print method

Direct thermal (ZD421d, no ribbon)

Resolution

203 dpi (8 dots/mm) standard, 300 dpi (12 dots/mm) optional

Print speed

203 dpi set to 51, 76, 102, 127, or 152 mm/s; 300 dpi up to 102 mm/s

Max print width

104 mm (203 dpi)

Media width

15-108 mm (ZD421d)

Label length

6.4-991 mm (min 12.7 mm with cutter or peeler)

Media roll

OD up to 127 mm, 12.7 mm and 25 mm cores standard (38.1, 50.8, 76 mm with adapters)

Interfaces

USB 2.0 (Type B), USB host, BLE for setup app

Wired options (field-installed)

10/100 Ethernet or RS-232 serial (DB-9), 1 module slot

Wireless

Field-installed: Wi-Fi 802.11ac + Bluetooth 4.2 module, or Wi-Fi 802.11ax + Bluetooth 5.3 module

Module installation

Tool-free installation, power loss recovery jumper (OFF at shipment)

Serial default settings

9600 bps, 8 bits, no parity, 1 stop bit, XON/XOFF

Printer languages

ZPL II, EPL2, EPL1 line mode (direct thermal 203 dpi model only)

Memory

512 MB flash, 256 MB SDRAM

Dimensions and weight

220.8 x 177.5 x 150.7 mm, 1.35 kg

The ZD421 direct thermal model (ZD421d) is Zebra's current 4-inch desktop printer that prints without a ribbon. Media width is 15-108 mm, the 203 dpi print width is 104 mm, and speed is set in 5 steps from 51 mm per second (2 ips) to 152 mm (6 ips).

The standard ports are USB 2.0 and USB host, and Ethernet, serial, and wireless are field-installed modules fitted later, so when you need a network you just buy the module and fit it yourself without tools.

Media width of the 3 ZD421 series models

Model	Print method	Media width	Size and weight
ZD421d	Direct thermal	15-108 mm	220.8 x 177.5 x 150.7 mm, 1.35 kg
ZD421t	Thermal transfer (ribbon roll)	15-112 mm	267 x 202 x 189 mm, 2.05 kg
ZD421c	Thermal transfer (ribbon cartridge)	15-118 mm	254 x 202 x 177 mm, 2.3 kg

4 field-installed connectivity modules

Wired modules go into the single module slot at the back, so choose one of 10/100 Ethernet (RJ-45, internal print server) or RS-232 serial (DB-9). To fit one, unplug the DC power plug from the back panel and press the top of the module cover with your fingertip to open it, exposing the slot.

Wi-Fi modules go inside the bottom cover, and there are two types, a Wi-Fi 802.11ac + Bluetooth 4.2 module and a Wi-Fi 802.11ax + Bluetooth 5.3 module, making 4 modules in all with the 2 wired ones. On a printer with a module installed, setting the module's power loss recovery jumper to ON makes the printer turn on automatically the moment AC power is supplied; the factory setting is OFF.

Cable specs and serial communication settings

Ethernet uses CAT-5 or better UTP (RJ-45) cable.
The serial cable must have a 9-pin male (DB-9P) connector on one end to plug into the female (DB-9S) port on the printer's back panel, and must be wired null-modem (crossover).
The factory serial settings are 9600 bps, 8 bits, no parity, 1 stop bit, and XON/XOFF; if the PC's baud rate or flow control differs, data does not get through.
Do not use RS-232 DTE/DCE conversion dongles; some dongles interfere with devices plugged into the USB host port when the printer turns on.

Use shielded data cables with metal-covered connectors, keep them as short as possible (1.83 m recommended), and do not bundle them with power cords.

ZD421 driver installation order

Install the Windows driver first with the Zebra installation tool (ZSU), and turn on the printer when the wizard tells you to. Connect cables with the printer power off, plugging in the power cord first and then the communication cable. If the order is reversed and power comes first, the printer shows up as an Unspecified item in the Windows device list; remove that item and then set up the driver again.

The old EPL1 line mode works only on the direct thermal 203 dpi model of the ZD421. Files are at ZD421 download.

FAQ

What is the difference between the ZD421 direct thermal model and the ZD421t?

The ZD421d prints only on direct thermal media without a ribbon and takes media 15-108 mm wide. The ZD421t loads 300 m and 74 m ribbon rolls to print thermal transfer and takes media 15-112 mm wide.

The ZD421 shows a media out warning even though media is loaded.

If one label is missing near the end of the roll, the roll manufacturer removed it on purpose to mark the end. Otherwise, set the movable sensor position to match the media, clean the upper gap sensor and the lower movable sensor, and calibrate again.

The label print position on the ZD421 drifts little by little.

Check that the sensor position is set for the media type (continuous, gap/notch, black mark), and in the ready state press PAUSE and CANCEL together for 2 seconds to run SmartCal calibration. If it still drifts, the platen roller is slipping or worn, so clean or replace it.