K7 – Audio Cassette with USB Flash Storage

Backstory:

I grew up in the '90s and still remember the charm of audio cassettes — the clicks, the rewinds, the mixtapes, and of course the classic pencil trick to rewind the tape.

I wanted to bring that feeling back by turning an iconic object into something both practical and proudly nostalgic. The design is slightly scaled up to fit modern tech but stays true to the spirit — with spinning reels, a display stand, and even a pen-shaped tool as a nod to the good old days. It adds a decorative touch and also helps with assembly if needed.

On the tech side, I used a flash drive and USB ports to neatly integrate storage into the print. I also included a slot for a NFC tag for those who want to add smart features like shortcuts, hidden messages, or links.

Note: The tape is scaled up to 112.5% length/width and 150% height compared to a real cassette, to fit USB components.

Included in the Set:

Cassette Tape

• face_A (1x)
• face_B (1x)

“Pins”

• big_pin (1x) – for the corners and to hold both faces together
• small_pin (1x) – mainly decorative, but they help align the USB connector in the center

“Tape reels”

• reel (1x)
• reel_insert (1x)

“magnetic tape”

• bottom_tape (1x)
• big_tape (1x)
• small_tape (1x)
   

tool (1x) (Looks like the classic pen used to rewind tapes. It adds a nostalgic touch and can assist with assembly if needed.)

Stand (Optionnal)

• stand (1x)
• stand_cap (1x)

Additional Materials:

For the cassette:

• 2x USB-3.0 A-Socket PCB, vertical angled - Reference econ connect: U3BU1AVW
• 1x SanDisk Ultra Flair 128Go USB 3.0 (available capacities: 16GB – 512GB)
• NFC tags (optional) 25mm ⌀ (I used NFC token from Wakdev)

For the Stand:
 

• 1x USB 3.0 adapter - Reference InLine :35300R
  To connect your storage (casette or stand) to your device (TV or computer)
• USB 3.0 Type A to Type A cable (male to male)

Technical Specifications:

• Printer used: Prusa Mini+
• Nozzle: 0.4 mm
• Layer height: 0.2 mm
• 4 perimeters | 6 bottom layers (1.2 mm) | 6 top layers (1.2 mm) | 15% infill.
• Filaments used: Polymaker Polyterra PLA

Printing Instructions:

Note: I used a brim on every part — this helps prevent warping on large parts and improves bed adhesion for smaller ones. Depending on the part, you may want to activate:

• Supports (for overhangs or visible geometry)
• The “Ironing” parameter (for a smoother top finish)

These are the settings I personally used, but feel free to adjust them to your printer and preferences. I’ve also included a reminder of how many pieces you need for each part.

USB connectors Instructions:

The USB components are connected with custom wiring, including a crossover between SSTX and SSRX lines, and standard USB 3.0 pin mapping.
Note: Be sure to test all connections to ensure full-speed USB 3.0 file transfers.

Assembly Instructions:

Note: Assembly is screwless. To avoid further issues, clean correctly all the support.

  1.  Place face_A and face_B flat on a stable surface (nice side facing up). Insert the small_pin into face_A and face_B. Tolerances are tight — use the large end of the Tool to push them into place. You will need to apply some force — be careful not to hurt yourself or damage the printed parts.

  2.  Flip face_A over and insert the 4 big_pin. Set face_B aside.

  3.  Assemble 2 reel by inserting a reel_insert between each pair. Glue is optional — the two cassette faces will hold everything in place.

  4.  Repeat step 3 for the second set of reel.

  5.  Insert the NFC token into its slot on face_A.

  6.  Place the 2 assembled reel into face_A.

  7.  Add the 2 bottom_tape, the big_tape, and the small_tape in their respective positions.

  8.  Insert the USB flash drive and the double_usb_ports into their slots.

  9.  Carefully align and press face_B onto the assembly. Clip it into place using the pins.

  10.  Adjust the small_pin if needed to center the USB connectors visually.

  11.  Check that both reel spin freely — for that sweet tactile satisfaction.

Optional: Display Stand

  12.  Insert the USB adapter into the stand.

  13.  Add the stand_cap and clip it securely.

  14.  Place the tool in the stand for decoration.