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ZD421 and ZD621 Series Desktop Printers User Guide
Setup
Connecting the Printer to a Device
Connecting Your Printer to a Computer
Wi-Fi and Bluetooth Classic Wireless Connectivity Option
ZD421 and ZD621 Desktop Printer User Guide
ZD421 and ZD621 Desktop Printer User Guide
About This Guide
Other Valuable Printer Resources
Zebra OneCare Printer Service and Support
Notational Conventions
Icon Conventions
Introduction
Link-OS 4 inch Desktop Thermal Printers
Common Desktop Printer Features
Link-OS 4-inch Desktop Printer Options
What’s in the Box?
Unpacking and Inspecting the Printer
What You Will Need to Print
Modes of Printing
Opening Your Printer
Closing Your Printer
Printer Features
Exterior Features of Your Printer
Inside the ZD421 Dual Capacity Ribbon Roll Printer
Inside the ZD621 Dual Capacity Ribbon Roll Printer
RFID Antenna Location – ZD621R Printers Only
Media Dancer – ZD621 Printers Only
Dual-Capacity Ribbon Chassis – Ribbon Roll Holders
Inside the ZD421 Direct Thermal Printer
Inside the ZD621 Direct Thermal Printer
Inside the ZD421 Ribbon Cartridge Printer
Accessing the Printhead of the ZD421 Ribbon Cartridge Printer
Label Dispenser Option (field-installable) – All Models
Cutter Option (field-installable) – All Models
Linerless Media Tear-Off Option – Direct Thermal Models Only
Linerless Cutter Option – Direct Thermal Models Only
Identifying Platen Drive Roller Types
Printer Power Supply Options
Attached Power Supply Base
Attached Battery Base and Battery
ZD621 Direct Thermal Locking Printer Feature – Healthcare Models Only
Zebra Print Touch for Near-Field Communications (NFC)
Controls and Indicators
User Interface
Standard Interface Controls
Meaning of the Indicator Light Patterns
Status – Typical Operating Conditions
Status – Printhead Operation
Status – Bluetooth Low Energy Option
Status – Ethernet (LAN) Option
Status – Wi-Fi (WLAN) Option
Battery Indicators and Controls
Install Hardware Options
Field-Installable Printer Accessories and Options
Printer Connectivity Modules
Accessing the Connectivity Module Slot
Installing the Serial Port Module
Installing the Internal Ethernet (LAN) Module
Removing Printer Connectivity Modules
Installing the Wireless Connectivity Module
Finding Your Printer's Media Access Control (MAC) Address
Media Handling Options
Removing the Standard Bezel
Installing the Label Dispenser
Installing the Standard Media Cutter
Media Roll Core Size Adapters
Installing the Media Roll Adapters
Installing the Attached Power Supply Base Options
Installing the Attached Battery Base Options
Installing the Battery into the Attached Power Base
Color Touch Display and Controls
Color Touch Display Printer Controls
Home Screen
Printer Status
Printer Info
Printer Wizards
User Menus
System Menu
System > Language
System > Program Language > Diagnostic Mode
System > Program Language > Virtual Device
System > Program Language > ZBI
System > Settings > Display Time Format
System > Settings > Password Level
System > Settings > Set Password
System > Settings > Power Up Action
System > Settings > Head Close Action
System > Settings > Screen Calibration
System > Settings > Restore Defaults
System > Settings > Print: System Settings
System > Energy Saving > Energy Star
Connection Menu
Connection > Networks > Reset Network
Connection > Networks > Primary Network
Connection > Networks > IP Port
Connection > Networks > IP Alternate Port
Connection > Networks > Print: Network Info
Connection > Networks > Visibility Agent
Connection > Wired > Wired IP Protocol
Connection > Wired > Wired IP Address
Connection > Wired > Wired Gateway
Connection > Wired > Wired MAC Address
Connection > WLAN > WLAN IP Protocol
Connection > WLAN > WLAN IP Address
Connection > WLAN > WLAN Subnet
Connection > WLAN > WLAN Gateway
Connection > WLAN > WLAN MAC Address
Connection > WLAN > ESSID
Connection > WLAN > WLAN Security
Connection > WLAN > WLAN Band
Connection > WLAN > WLAN Country Code
Connection > Bluetooth > Bluetooth
Connection > Bluetooth > Bluetooth Discovery
Connection > Bluetooth > Friendly Name
Connection > Bluetooth > Minimum Security Mode
Connection > Bluetooth > Specification Version
Connection > Bluetooth > MAC Address
Connection > Bluetooth > Bluetooth Auth. PIN
Connection > Bluetooth > Bluetooth Bonding
Print Menu
Print > Print Quality > Darkness
Print > Print Quality > Print Speed
Print > Print Quality > Print Type
Print > Print Quality > Label Type
Print > Print Quality > Label Length
Print > Print Quality > Label Width (Dots)
Print > Label Position > Collection Method
Print > Label Position > Tear Line Offset
Print > Label Position > Horizontal Label Offset
Print > Label Position > Vertical Label Offset
Print > Sensors > Manual Calibration
Print > Sensors > Label Sensor
Print > Sensors > Sensor Type
Print > Sensors > Print: Sensor Profile
Print > Print Station
Print > Applicator > Applicator Port Mode
Print > Applicator > Start Print Mode
Print > Applicator > Error on Pause
Print > Applicator > Applicator Reprint
RFID Menu
RFID > RFID Status
RFID > RFID Test
RFID > RFID Calibrate
RFID > Read Power
RFID > Write Power
RFID > RFID Antenna
RFID > RFID Valid Count
RFID > RFID Void Count
RFID > RFID Program Position
RFID > Read RFID Data
Storage Menu
Storage > USB > Copy: Files to USB
Storage > USB > Copy: Files to Printer
Storage > USB > Copy: Configuration to USB
Storage > USB > Print: From USB
Storage > Print Asset Lists
Storage > USB > Print from E:
Setup
Modifying or Viewing Secured Features
Printer Setup Overview
Select a Location for the Printer
Install Printer Options and Connectivity Modules
Attaching the Printer to a Power Source
Media Preparation for Printing
Preparing and Handling Media
Media Storage Guidelines
Roll Media Types and Loading
Setting Media Sensing by Media type
Loading Media
Movable Sensor Adjustment
Adjusting the Movable Sensor for Black Marks or Notches
Adjusting the Movable Sensor for Web (Gap) Sensing
Loading Roll Media for Cutter Models
Thermal Transfer Roll Ribbon Loading
Loading Zebra Transfer Roll Ribbon
Loading Non-Zebra 300-Meter Transfer Ribbon
Loading the Ribbon Cartridge – ZD421 Ribbon Cartridge Printers Only
Running a SmartCal Media Calibration
Test Printing with a Configuration Report
Detecting and Recovering from a Media-Out Condition
Detecting and Recovering from a Ribbon-Out Condition
Connecting the Printer to a Device
Connect to a Phone or Tablet
Connecting Your Printer to a Computer
Interface Cable Requirements
USB Interface
Serial Interface
Ethernet (LAN, RJ-45)
Wi-Fi and Bluetooth Classic Wireless Connectivity Option
Update Printer Firmware to Finish Option Installations
What To Do If You Forget to Install the Printer Drivers First
Setup for Windows
Windows-to-Printer Communication Setup (Process Overview)
Installing the Windows Printer Drivers
Running the Printer Installation Wizard
Setting Up the Wi-Fi Print Server Option
Configuring the Printer Using ZebraNet Bridge’s Connectivity Wizard
Sending a ZPL Configuration Script to the Printer
Configuring the Printer Using Bluetooth
Connecting the Printer to a Windows 10 OS
After Your Printer is Connected
Test Printing with Zebra Setup Utilities
Test-Printing with the Windows Printer and Faxes Menu
Test-Printing with an Ethernet Printer Connected to a Network
Test-Printing with a Copied ZPL Command File for Non-Windows Operating Systems
Print Operations
Thermal Printing
Determining Your Printer’s Configuration Settings
Select a Print Mode or Collection Method
Adjusting the Print Quality
Adjusting the Print Width
Replacing Supplies while Using the Printer
Printing on Fanfold Media
Printing with Externally-Mounted Roll Media
Using the Label Dispenser Option
Using the Linerless Options
Linerless Printing
Sending Files to the Printer
Ribbon Cartridge Programming Commands
Printing with the Attached Battery Base and Battery Option
Uninterrupted Power Supply (UPS) Mode
Battery Mode
Printer Fonts
Identifying Fonts in Your Printer
Localizing the Printer with Code Pages
Asian Fonts and Other Large Font Sets
EPL Line Mode (Direct Thermal Printers only)
ZD621 Locking Printer Option
Zebra Keyboard Display Unit (ZKDU) – Printer Accessory
Zebra Basic Interpreter (ZBI)
Setting the Power Failure Recovery Mode Jumper
USB Host Port and Link-OS Usage Examples
USB Host
Using a USB Host for Firmware Updates
Files for Completing the Exercises
Exercise 1: Copy Files to a USB Flash Drive and Perform USB Mirror
Exercise 2: Print a Label Format from a USB Flash Drive
Exercise 3: Copy Files to/from a USB Flash Drive
Exercise 4: Enter Data for a Stored File with a USB Keyboard and Print a Label
Using the USB Host Port and Near Field Communication (NFC) Capabilities
Exercise 5: Enter Data for a Stored File with a Smart Device and Print a Label
Maintenance
Cleaning
Cleaning Supplies
Recommended Cleaning Schedule
Cleaning the Printhead
Cleaning the Printhead – ZD421/ZD621 Direct Thermal Printers
Cleaning the Printhead – ZD421/ZD621 Thermal Transfer Printers
Cleaning the Printhead – ZD421 Ribbon Cartridge Printers
Cleaning the Media Path
Cleaning the Media Path – Lower Half of ZD421/ZD621 Printers
Cleaning the Media Path – Upper Half of ZD421/ZD621 Direct Thermal Printers
Cleaning the Media Path – Upper Half of ZD421/ZD621 Thermal Transfer Printers
Cleaning the Media Path – Upper Half of ZD421 Thermal Transfer Ribbon Cartridge Printers
Cleaning the Cutter Option
Cleaning the Label Dispenser Option
Cleaning the Sensor
Cleaning the Sensor – Lower Half of the ZD421/ZD621 Printers
Cleaning the Sensor – Upper Half of ZD421/ZD621 Direct Thermal Printers
Cleaning the Sensor – Upper Half of the ZD421/ZD621 Thermal Transfer Printers
Cleaning the Sensor – Upper Half of the ZD421 Ribbon Cartridge Printers
Cleaning and Replacing the Platen
Replacing the Printhead
Replacing the Printhead – ZD421/ZD621 Direct Thermal Printer Models
Replacing the Printhead – ZD421/ZD621 Thermal Transfer Ribbon Roll Printer Models
Replacing the Printhead – ZD421 Thermal Transfer Ribbon Cartridge Printer Models
Updating Printer Firmware
Other Printer Maintenance
Fuses
Troubleshooting
Resolving Alerts and Errors
Alert: Printhead Open
Alert: Media Out
Alert: Ribbon In – ZD421 Ribbon Cartridge Printer Only
Alert: Ribbon Out
Alert: Ribbon Low – ZD421 Ribbon Cartridge Printer Only
Alert: Cutter Error
Alert: Printhead Over Temp
Alert: Printhead Shutdown
Alert: Printhead Under Temp
Alert: Out of Memory
Resolving Print Issues
Issue: General Print Quality Issues
Issue: No Print on the Label
Issue: Labels Are Distorted in Size or Print Area Start Position Varies
Printer Connectivity Issues
Communication Issues
Issue: Label Job Sent, No Data Transfer
Issue: Label Job Sent, Skips Labels or Prints Bad Content
Issue: Label Job Sent, Data Transfers, But No Print
Miscellaneous Issues
Issue: Settings are Lost or Ignored
Issue: Printer Prompting for Front Panel Password
Issue: Non-continuous labels act as Continuous labels
Issue: Printer Locks Up
Issue: Erroneous Ribbon Cartridge Faults
Issue: Battery Displays a Red Indicator
Tools
Printer Diagnostics
Power-On Self Test
Running a SmartCal Media Calibration
Printing the Printer and Network Configuration Reports (CANCEL Self Test)
Network (and Bluetooth) Configuration Report
Printing a Print Quality Report (FEED Self Test)
Printing a Print Quality Report
Resetting Defaults
Resetting Non-Network Printer Configuration Settings to their Factory Defaults
Resetting the Printer's Network Settings to Their Factory Defaults
RESET Button Functions
Performing a Communication Diagnostics Test
Sensor Profile
Activating Advanced Mode
Manually Calibrating Media
Manual Print Width Adjustment
Manual Print Darkness Adjustment
Factory Test Modes
Interface Connector Wiring
Universal Serial Bus (USB) Interface
Serial Port Interface
Dimensions
Dimensions – ZD421/ZD621 Direct Thermal Printer Models
Dimensions – ZD421/ZD621 Thermal Transfer Printer Models
Dimensions – ZD421C (Ribbon Cartridge Thermal Transfer) Printer Models
Media
Types of Thermal Media
Determining Thermal Media Types
General Media and Print Specifications
ZPL Configuration
Managing the ZPL Printer Configuration
ZPL Printer Configuration Format and Reusable Files
Configuration Setting to Command Cross-reference
Printer Memory Management and Related Status Reports
ZPL Programming for Memory Management
Glossary
alphanumeric
backfeed
barcode
black mark media
calibration (of a printer)
collection method
configuration
continuous media
core diameter
diagnostics
die-cut media
direct thermal
direct thermal media
fanfold media
firmware
FLASH memory
font
gap/notch media
ips (inches-per-second)
label
label backing (liner)
label type
void
LCD (liquid crystal display)
LED (light emitting diode)
linerless media
mark media
media
media sensor
media supply hangar
non-continuous media
non-volatile memory
notched media
peel-off mode
perforated media
print speed
print type
printhead wear
Radio frequency identification (RFID) "smart" media
receipt
registration
ribbon
ribbon wrinkle
roll media
supplies
symbology
tag stock
tear-off mode
thermal transfer
Wi-Fi and Bluetooth Classic Wireless Connectivity Option
Wi-Fi and Bluetooth Classic Wireless Connectivity Option
For printers purchased in the EMEA region after August 1, 2025, certain connectivity options are disabled by default. To enable these options, refer to the
Zebra Link-OS PrintSecure Printer Administration Guide
.
This user guide covers only basic configuration of your Internal Wi-Fi Print Server and Bluetooth Classic 5.3 wireless connectivity options as described in
Setting Up the Wi-Fi Print Server Option
and
Configuring the Printer Using Bluetooth
.
For details on your printer's Ethernet and Bluetooth operations, see the Wired/Wireless Print Server User Guide and the Bluetooth Printer Management Guide available from
zebra.com
.
Connecting Your Printer to a Computer
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