Design of the Week: Combination Lock Pen

By on August 15th, 2022 in Design, news


The 3D printed Combination Lock Pen [Source: Probably_Capable / Reddit]

This week’s selection is the Combination Lock Pen by Reddit contributor Probably_Capable.

The Combination Lock Pen is perhaps the 3D printed item that is the most complex and at the same time the most impractical. In other words, a perfect 3D print!

What does it do? It includes a numerical rotating combination lock that must be unlocked in order to push the pen tip out for writing. If you don’t know the combo, you can’t write!

Of course, you could simply disassemble the Combination Lock Pen and get it working, or more practically, use another pen that doesn’t have a lock on it. Hence the impractical nature of this pen technology.

Amazingly, most of the design is 3D printed, with only minimal non-printed components. Probably_Capable said:

”I wanted this to be as much as printed parts as possible. It only uses the pen reservoir and spring out of a G2 pen. The clicky mechanisms would either need to be massive to work properly or too small for my printer. Maybe when I finally decide to get myself a resin printer I’ll revisit the the design.”

FreeCAD used to design the 3D printed Combination Lock Pen [Source: Probably_Capable / Reddit]

Probably_Capable apparently used FreeCAD to design the semi-complex pen, and seems to have 3D printed the parts on a desktop 3D printer.

Printing the 3D printed Combination Lock Pen [Source: Probably_Capable / Reddit]

Why go to all the trouble of making a combination lock pen when it be stolen anyway? Probably_Capable explained:

“I don’t care if they steal it, I just don’t want them using it. In actuality this pen was made from a joke between a coworker and I. It has no practical function, but it does function.”

As you might imagine, 3D printing the parts to this mechanism could be quite challenging: they must have very good dimensional tolerances and some strength. If not, then the mechanism could jam up or not work at all.

Parts and version of the 3D printed Combination Lock Pen [Source: Probably_Capable / Reddit]

Somehow, through multiple iterations, Probably_Capable was able to produce these parts on a FFF desktop 3D printer, and the pen actually works, as you can see in this video:

Do you need a Combination Lock Pen? Absolutely not. But do you need to try to design something as complex and useless as this? Absolutely!

In the end, I think Probably_Capable is actually Quite_Capable, don’t you?

Via Reddit and Reddit

By Kerry Stevenson

Kerry Stevenson, aka "General Fabb" has written over 8,000 stories on 3D printing at Fabbaloo since he launched the venture in 2007, with an intention to promote and grow the incredible technology of 3D printing across the world. So far, it seems to be working!

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