The ZD420d is a 4-inch direct thermal printer that switches between 203 dpi and 300 dpi with a kit that replaces the head and platen roller. It is a discontinued model, and the direct thermal model takes media up to 108 mm wide, 10 mm narrower than the ZD420 thermal transfer model, which takes up to 118 mm. The ZD420 models that use a ribbon are covered separately on the ZD420t ribbon roll model and ZD420c cartridge model pages.
Resolution conversion kit for switching between 203 dpi and 300 dpi
Besides having the resolution set at the factory, the ZD420d can be changed from 203 dpi to 300 dpi, or the other way, with a kit while in use. The kit contains both a head and a platen roller, and both are resolution-specific, so do not change only one.
- Turn off the power and unplug the power cable.
- Replace the platen roller with the new kit roller. Rollers are color-coded by resolution.
- Replace the head. The kit head is marked 203 or 300, so it is not confused with the original head (unmarked).
- When you turn the power on, the boot check detects the head change by itself. Boot completes normally even if the roller was not changed, so step 2 is easy to miss.
Switching to 300 dpi widens the print width by 4 mm to 108 mm, and lowers max speed from 152 mm per second to 102 mm.
Battery and hospital lock options
The battery base is a field-installed option that attaches to the bottom of the printer. After unplugging the power cable at the back of the printer, on the direct thermal model tighten 3 screws with the Torx T10 wrench included in the kit. After inserting the battery, plug the printer power supply into the battery. The battery ships in shutdown mode for safety, so connecting the power supply releases shutdown mode and starts the first charge, which takes about 2 hours to full.
The media lock cabinet, available only on the direct thermal healthcare model, locks the label roll with a two-key mechanical lock and a Kensington slot.
The 2 mm 300 dpi users lose on the ZD421
A ZD420d used at 300 dpi has a 108 mm print width, but the current ZD421 direct thermal model has a 300 dpi print width of 106 mm. Layouts that fill the full 108 mm to the edges must be narrowed by 2 mm before moving to the ZD421. The 203 dpi width (104 mm), 108 mm media width, and body dimensions (220.8 x 177.5 x 150.7 mm) do not change; only the weight drops from 1.6 kg to 1.35 kg.
The driver for both 203 dpi and 300 dpi is posted in the ZD420 downloads.
