A shipping label printer takes a digital label, moves a roll of label stock past a printing element, and puts an image on it, usually in a single black colour. Most work with heat rather than liquid ink, which keeps the design simple: a roll, a roller, a printhead and a sensor.
The Four Parts That Matter
- The roll holder keeps the stock in place and lets it unwind smoothly.
- The platen roller is a rubber cylinder that presses the stock against the printhead and pulls it forward.
- The printhead is a strip of tiny elements that make the image one line at a time.
- The sensor detects where each label begins and ends, so the print lands in the right place.
From Screen to Sticker
Here is the usual sequence when you press print.
- Your computer sends the label data and the chosen size to the printer.
- The printer reads the size and checks the sensor for the gap or mark between labels.
- The roller moves the stock forward in small steps.
- With each step, the printhead builds one thin line of the image.
- When the final line of the label is done, the stock advances to the cut or tear point.
The barcode is a pattern of lines and spaces, so line-by-line printing suits it well. That is also why a dirty printhead causes streaks that cut across the code.
Two Ways of Making the Image
| Method | How the mark is made | Typical use |
|---|---|---|
| Direct thermal | Heat darkens a coating built into the label stock | Shipping labels with a short life |
| Thermal transfer | Heat moves a ribbon coating onto the label | Labels that need to stay readable longer |
Both depend on stock made for that method, so always match the roll to the printer type described in the maker’s guide.
What the Software Does
The driver, or a shipping account’s print setup, turns the page into a bitmap at a resolution the printer can handle. It also sets the width, height and darkness. If the size does not match the roll, the label may be cropped or shifted, which is a settings issue rather than a fault in the machine.
FAQ
Why does the printer feed a blank label sometimes?
The sensor may have lost the position of the gap, and calibration usually restores it. Follow the maker’s guide for the exact routine.
Why do some labels fade over time?
Heat-sensitive coatings can darken or lighten with warmth, light and rubbing. If a label must last, look at the stock type and the maker’s storage advice.
The Short Version
A roller pulls label stock past a printhead that builds the image line by line, while a sensor keeps everything lined up. Software sets the size and darkness, and the stock must suit the printing method.