CNC Engraving

Warning/Disclaimer: This feature is intended for individuals with experience in electronics tinkering and soldering.

Krux engraves any QR code (SeedQR, PSBT, address, XPUB, etc.) on GRBL 1.1 CNC machines — via airgapped SD card or direct TTL serial connection.

A GRBL g-code simulation on OpenBuilds CONTROL:

After configuring the CNC printer and driver in settings, any screen that displays a QR code will offer to Print as QR. Use this to Carve QR codes into wood/metal, like backups of your mnemonics, xpubs and multisig wallet output descriptor.

If the driver is configured as FilePrinter, the output will be GRBL g-code in a qr.nc file on the SD card. If the driver is configured as GRBLPrinter, the output will be GRBL g-code sent directly to a GRBL controller via a TTL serial connection. A tested settings is presented below:

"cnc": {
    "unit": "mm",
    "part_size": 70.675,
    "flute_diameter": 3.175,
    "depth_per_pass": 1.0,
    "cut_depth": 2.0,
    "border_padding": 2.0,
    "plunge_rate":300,
    "feed_rate":650,
    "cut_method": "spiral",
    "invert": 1
}

A 96×96mm QR carved into black-painted wood with 2mm drill-bit (inverted for white):

A 50x50mm QR carved into black-painted wood with 2mm drill-bit (inverted for white):

Laser etching is also supported. Tested settings and results:

"cnc": {
  "unit": "mm",
  "part_size": 34,
  "flute_diameter": 0.2,
  "depth_per_pass": 0.01,
  "cut_depth": 0.01,
  "border_padding": 0.0,
  "plunge_rate": 150,
  "feed_rate": 300,
  "cut_method": "row",
  "invert": 0,
  "head_type": "laser",
  "head_power": 500
}

From left to right: 34x34mm at 50%, 21x21mm at 5%, 21x21mm at 50% power laser-etched stainless steel:

Note: Just be careful what you do with the printed codes, since most smartphones can now quickly and easily read QR codes. Treat your QR mnemonic the same way you would treat a plaintext copy of it.