Mobile Phone Lock Box

Lock up phones to avoid distractions.  Not just for classrooms…this can also be used for family time, game night, dinner parties, or simply to avoid temptation of checking the phone in the middle of the night (lock up the phone and put the key at the other end of the house).  Also great for preventing co-workers from doing productive work on their phones during useless meetings.

2025-04-22 Update: Per request, added the 4-phone model in STEP format in case someone wants to modify it.

Design Features:

• Print-in-place lock mechanism (with snap-on back cover).
• No supports required
• Only 2 screws required (for the hinges).
• Stackable design to allow more phone storage.
• Pass-through on the back to allow charging while locked up.
• Two box designs:
  • 8-phone box for regular phone cases
  • 4-phone box with double-wide chambers for large phone cases

Key Lock Operation:

The key can be removed in either the locked or unlocked position.  There is an internal locking tab attached to the lock cover that prevents the lock cylinder from rotating when the key is removed.

IMPORTANT: when inserting the key, push it all the way in until the key is flush with the front surface of the lock.  This disengages the locking tab on the lock cover so that the lock cylinder can rotate.  Attempting to rotate the key without first pushing it all the way in will be very difficult, and could eventually break the locking tab.  If for some reason the locking tab does break, it can be fixed by simply printing and attaching a new lock cover.

Parts Required:

• 2 x M3x16mm Socket Head Cap Screws (one for each hinge).  I used these screws: https://www.amazon.com/M3-0-5-Socket-Screws-Marine-Stainless/dp/B07DVQKWFP

Printing Notes:

• Print using PLA at 0.2mm layer height, 0.4mm nozzle, and 15% infill.
• Supports are not required for any of the parts.
• Please don’t use the .bgcode files that have been provided (always slice your own files for your specific printer, filament, environment, etc.).  The files were included to provide a reference for approximate print time.

Assembly Instructions (refer to photos):

Lock Assembly:

1. Insert the key and turn it a couple times to ensure that the lock cylinder is moving freely.
2. Insert the the end of the lock cover into the slot on the lock mechanism.
3. Press the other end of the lock cover until it clicks into place.

Hinge Assembly:

1. Line up the door with the box, and insert the 2 hinge screws.  Do not over-tighten the screws.

Miscellaneous Notes/Comments:

• If you want to see how the lock mechanism works, the “Extras” folder contains a see-through lock cover that can be installed in place of the regular lock cover.
• The “Extras” folder also contains a thick wall version of the 8-phone box that is much stronger (if the box is expected to be subject to severe abuse).