Sep 13, 2015

3D Printed Porcupine Pen Holder

I recently told a crowd of people that I feel a small adrenaline rush when I see arts and crafts supplies. Sounds crazy, unless you can relate to it, but even the sight of a large colorful set of Sharpies makes me want to create something. That got me thinking that while I have lots of those supplies, I rarely see them during a normal day - and I wanted to change that.

The Problem

I have a couple of dozen colorful Sharpie markers in my draw, or sometimes in a pile on my desk, since those sets almost always come in those annoying plastic covered cardboard packages with nothing useful for storage. It occurred to me that a rainbow of creative colors like that should be on display - always - to inspire creativity and simply look good. If you follow this blog, you know I even put Sharpies to good use when coloring 3D Printing projects.

The Design Idea

I decided on a whim to create a functional pen holder that would also look good on my desk by showing off the colors of the markers. The image in my mind was a "porcupine" or "sea urchin" pattern - where the colors of the pens could really be shown and the pens could be easily inserted and retrieved.

The 3D Model

I first created one individual holder without a base - just a hollow cylinder. Measuring my Sharpie markers, it seemed 12.5mm inside diameter would be enough to hold most pretty firmly - and 1.75mm walls would be strong enough. I created a cylinder with a 16mm outside diameter and hollowed it out so it had 12.5mm open inside. It was made 40mm tall to give plenty of support to pens which are about 140mm long.

Now I could replicate that one holder as many times as I wanted and put it on a base.
NOTE: I always tell people to actually 3D print smaller versions of your models before committing to large prints. This helps avoid the avoidable fail. In this case I SHOULD HAVE printed one of these cylinders to test it - but I didn't. It turned out fine - but I still stand by that approach of testing small parts of your model before committing to a 9 hour print (oops I just gave away how long this took to print).

Get the Porcupine Pen Holder Model File on my Page

Creating Symmetry

Trying to create symmetric geometry in my 3D Modeling app (Autodesk 123D Design) was a bit harder than I first expected. I wanted the holder to be stable - so it needed a wide base.  I also wanted the individual holders to be exposed (rather than be inset holes in a block) so that it looked porcupine-like even without any pens in it.  The base I envisioned would be a "Spherical Cap" - that is a cut off part of a sphere - with the pen holding cylinders sticking out in a perfectly geometric pattern.

Turns out there is no great way to position cylinders evenly spaced and correctly angled on the surface of a sphere. The method I came up used the SNAP tool which puts a face of one object perfectly on the face of another object. Even though that tool snaps to the same spot on a cylinder or sphere, I found I could snap one cylinder, then rotate the sphere and snap again - repeating that for the number of holders I wanted and being careful to rotate on the planes the same distance each time.

I actually used large cylinders as the base to get that rotate/snap pattern working on one plane at a time, and then rotating a duplicate of the whole thing on the z-axis - but after all that work, I realized I could have done it all on the sphere in the first place.

The Result

 This was a large model - probably my largest since the School Locker Pencil Cup I created several months ago (what is it with me and pen/pencil holders!). The estimated time to print was 8 hrs 34 min from Cura and it actually took 9 hrs 7 min to complete (overnight, of course) on my Lulzbot TAZ4.

The resulting pen holder works beautifully and achieved my vision for keeping lots of color and creativity within view and within reach! I've got lots of ideas on how to make this design even better.

Ideas For Version 2.0

Seeing this thing in action gave me a bunch of ideas for improvement or just interesting design alterations:

> Add a flat surface on the base for simple personalization (company name, twitter handle, etc).
> Flatten the top of all the cylinders on the same plane
> add a business card holder in front
> add a ring of straight standing holders around the perimeter
> make a square block which has the same pattern of pen holders inset into it.

Share your ideas please in the comments!


  1. Hello JR. Good to meet a fellow addict ;). I am lucky I have a little space where to work now . I have filled it quickly with lots of colour (and stationary,of course). Whenever I am there, I look around, I smile, feel good inside and enthused to try something new. Best of luck with your designs.

  2. can pens be stored cap down so you can easily replace the pen after using?