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July 17, 2014 AT 6:00 am

Mechanical Pencil #3DxReplica #3DThursday #3DPrinting

3D Printed Mechanical Pencil:

…I went though a couple prototypes where I was just modifying the standard mechanical pencil design (“hysteresis collet”) for printing. It didn’t take long before I accepted that the standard design is ill suited for printing – there is too much reliance on spring force and tight fitting parts. The only way I had around that obstacle was to reinvent the design for 3D printing. I came up with a couple of concepts but settled on a lead-screw design.
 
In this design, the lead is pushed out incrementally by rotating the back of the pencil, which rotates a screw. There are 12 detents per revolution that allow the lead to be locked in position. These detents give a nice “click” sound when the back end is rotated. Rotating it clockwise will push the lead out about 1.2mm per click. Rotating in the opposite direction will allow the lead to be pushed back into the pencil. The back end can also be popped apart from the pencil which allows the lead to be fully back driven. In this mode, the detent mechanism is declutched from the screw so that any force applied to the lead will cause it to back drive the screw and retract into the pencil.

At the front of the pencil, 3 small fingers grab the lead and apply some friction to prevent the lead from falling out of the pencil. New lead is inserted through the tip….

Read More.

Pasted Image 7 16 14 11 51 PM

Pasted Image 7 16 14 11 52 PM


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Every Thursday is #3dthursday here at Adafruit! The DIY 3D printing community has passion and dedication for making solid objects from digital models. Recently, we have noticed electronics projects integrated with 3D printed enclosures, brackets, and sculptures, so each Thursday we celebrate and highlight these bold pioneers!

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