Tuesday, January 26, 2016

3D printing a key

The apartment I'm renting is missing a key for the living room so I thought a nice experiment would be to try to print one of PLA. I already saw a talk at 32C3 that PLA has sufficient strength to actuate a lock without breaking.

I took a photo of the lock and did some basic processing (in MS Paint) to make it easier for the https://keysforge.com website to parse it:

I currently cannot get the website to work again but here is the key that was generated from the keyhole shot above:

After a miniature print I realized it needed a 2x scaling. Some dremel work a bit later:

The underside of the key was removed to make a 'tongue' that is able to catch the latch. Even though the print was done with 80% infill it still broke at the second twist, without ever opening the lock.

The next tenant might be surprised to find a piece of PLA as I was surprised to find 5 1-cent coins inside:

I already had a similar looking key, but with a mirrored pattern. Some more dremel work later I got a functioning key:

The protruding part on the lower right was cut and the upper left side was trimmed a bit.

Time it took to preprocess, print, reprint, postprocess the PLA key: >2 hours
Time it took to modify the lock: 10 minutes

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