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NFC tags

Which tags work, how the scale reads them, and how it writes them.

Reading

Put a spool on the pad. The scale reads the tag, looks it up at your backend and shows the spool. That is the whole interaction.

A spool from an NTAG with an OpenSpool record

  • NTAG stickers are found by their UID. It is stored as plain hex (04B9E542447080), the same way every other tool around Spoolman does it, so links made elsewhere are found here and the other way round.
  • Bambu Lab tags are read and decrypted: material, colour and the spool come up by themselves.
  • MIFARE Classic cards and stickers are found by their UID. A card your backend knows shows up after 3 to 5 seconds, an unknown one after about ten.
  • Snapmaker tags can be read as well. Switch on Read Snapmaker tags in the web interface under Settings. It is off by default because it slows down other MIFARE tags a little.

The tag view

Tap the NFC chip in the header to see what is on the tag on the reader. For an NTAG, Erase empties it and Write spool #N writes the spool on the screen onto it.

The tag view with Erase and Write spool #12

Writing

The scale also writes tags, with every backend, and needs nothing special on the server for that.

Writing replaces everything on the tag

Whatever is on the tag now is lost. Bambu tags are never written.

Settings → Scale → Write tag after linking

Tag writing options

  • Off - only the UID is bound to the spool, the tag is left alone.
  • Ask - the scale asks every time.
  • Write every time - no question, only the result is reported.

A card with a progress bar asks you to leave the spool where it is while the scale writes. Ask on a mismatch on the same screen lets the scale offer a rewrite later, when the tag no longer matches the spool.

Formats

Material, colour, brand, temperatures and the spool ID, readable by filament managers and OpenSpool readers. The default, and the right choice unless you have a reason otherwise.

The same record under the name FilaMan expects. Pick this if FilaMan is your backend and you want its own readers and app to pick the tag up.

The raw pages the Anycubic ACE reads itself. For feeding the printer directly rather than a filament manager.

From the browser

The Tags page in the web interface shows what is on the tag next to what would go on it, and lets you pick the format. There you can also link a tag without writing it (Link only) and look at the tag's raw data. The tag has to be on the reader.

A second tag per spool

A tag on each side of the spool means it is found whichever way round it lies. Right after a link the scale asks for the second one: turn the spool over, done. Switch the question on or off under Settings → Connection → More options → Ask for a second tag.

This needs a backend that can hold more than one tag per spool: Spoolman 0.27 or newer with native tags (or the card_uids field), or FilaMan 1.3.1 or newer. BamBuddy cannot.

If you link a tag that already belongs to another spool, the scale shows both spools and offers to Move it.

Happy Hare

Happy Hare reads the chip's hardware UID from the rfid_tag field. Switch on Also write the chip UID (Spoolman only, under More options) and the scale fills it in for you.

Which tag should I buy?

NTAG215. It reads reliably and has room for a record if you want the scale to write it.

Tag Read Write Notes
NTAG213 yes no 144 bytes, too small for a record
NTAG215 yes yes recommended
NTAG216 yes yes more memory, slightly pricier
MIFARE Ultralight yes no very stable to read
MIFARE Classic, Creality, Snapmaker yes no by UID
Bambu Lab yes never encrypted
ISO 15693, Prusa OpenPrintTag no no a different radio standard

Round 25 mm stickers are the most common and sit well on spool hubs.

Positioning - closer is not better

The most common cause of unreliable reads is the opposite of what most people expect: a tag pressed directly against the reader often reads worse than one a few millimetres away. At very close range the tag detunes the reader's antenna, and the field collapses.

If a tag reads badly, add distance before replacing it

A gap of roughly 5 to 20 mm is the sweet spot for most sticker tags. A few layers of foam tape or a small printed spacer under the tag is usually all it takes.

  • Do not stick the tag onto metal or over a metal spool insert.
  • The spool can only shift a little on the plate, so the distance has to come from the tag side.

Bambu Lab spools rarely show this because their tag sits recessed inside the spool core.

Lost reads and the location question

Now and then the reader briefly loses an NTAG although the spool has not moved. The location question does not fall for it: it checks the weight and only comes when you really lift the spool.

Below 50 g, or on a device without a load cell, the scale has only the reader to go by. If the location list then opens on its own, check the positioning above, or switch off Location on removal under Settings → Scale.