Core size, roll diameter and winding: what to check
A label roll can have the right label size and still not fit your printer. Three features of the roll decide compatibility.
1. The core
The core is the cardboard tube in the middle of the roll. Common inner diameters:
| Core | Mostly used on |
|---|---|
| 1″ (25 mm) | Small desktop printers, short rolls |
| 1.5″ (38 mm) / 40 mm | Desktop printers, medium rolls |
| 3″ (76 mm) | Industrial printers, label applicators, large rolls |
A printer’s roll holder takes a range of cores. Many desktop models have an adjustable holder that fits several sizes. A core that is too large won’t go on; one that is too small can wobble on the spindle and make the roll track off-centre.
2. The outer diameter
This is the diameter of the full roll. The printer’s roll bay sets a maximum, stated in its data sheet. Bigger rolls mean fewer changes, but above the maximum the cover won’t close or the roll rubs.
To work out the diameter for a given number of labels, or the other way round, use the roll calculator. For the same number of labels, a larger core gives a larger roll.
3. The winding direction
Labels can be wound outside (printable face visible) or inside (face towards the core). Desktop thermal printers are almost always designed for labels wound outside.
For pre-printed labels used on applicators and dispensers, the orientation of the print relative to the feed also matters: which edge comes off the roll first. Suppliers describe it with a winding position number, but numbering varies, so always send a diagram or describe it in words when you order.
Other things to check
- Maximum roll width, liner included. A 100 mm label on a 104 mm liner needs a printer that takes 104 mm.
- Sensing type: gap between labels, black mark on the back, or notch. The sensor must be set to match.
- Print method: direct thermal or thermal transfer with a ribbon. See direct thermal or thermal transfer.