QR code keychain for 3D printing
A keychain that opens your link, your review form or your Instagram. Ring hole included, two colours, and a size check that tells you the truth before you print.
The link length decides how big the keychain has to be
This is the one constraint people meet first. A QR code grows in modules as the data grows, and each module has to stay above about 1.2 mm to survive a 0.4 mm nozzle. Longer link, more modules, bigger keychain.
Concretely: a short g.page/r/…/review link fits on a 45 mm keychain. The long search.google.com/local/writereview?placeid=… form of the same destination does not fit at 50 mm — the generator blocks it rather than producing something unscannable.
So if you want a small keychain, shorten the link first. A short link is not a nice-to-have here, it is the difference between a 45 mm keychain and a 70 mm one.
The ring hole
The hole is 4.5 mm across with a wall around it thick enough not to tear — that takes a standard split ring, a lanyard clip or a carabiner. It is modelled as part of the plate, not drilled through afterwards, so there is no thin shell to crack.
What people make them for
Event giveaways that link to a schedule or a photo album. Trade-show handouts that beat a business card because nobody types a URL from a card. Pet tags pointing at a contact page. Staff keys linking to a shift rota.
Add your business name in raised text under the code and it works as a physical business card that survives a pocket.
Printing advice
Flat on the bed, no supports. Two colours give the code its contrast — dark plate, light code, or the reverse. With a single extruder, insert a colour change at the layer where the code begins; the relief is 0.8 mm, so four layers at 0.2 mm.
Any rigid filament works. PETG survives a pocket and a keyring better than PLA if it will be carried daily.
Frequently asked questions
How small can a QR keychain be?
About 45 mm for a short link. Smaller than that pushes the modules below the printable minimum and the code stops scanning reliably. The tool tells you the module size for your link and refuses to export when it is too small.
Why does my link length change the size?
A QR code holds more data by adding more modules, not by growing. More modules in the same physical width means each one is smaller, and below roughly 1.2 mm a 0.4 mm nozzle cannot reproduce them. Shortening the link is the cheapest way to shrink the keychain.
What ring fits the hole?
The hole is 4.5 mm, which takes a standard split ring, a lanyard clip or a small carabiner.
Which filament should I use?
Any rigid filament prints fine. PETG holds up better than PLA for something carried in a pocket every day.
Design my keychain
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