This week, I set out to make something for my desk. Since I’ve been working with lots of kid’s storybooks, there is currently a pile of books on my desk that topples over at least once a day. So naturally, I wanted to make a bookshelf.

The first thing I started thinking of is: books are heavy. One sheet of cardboard cannot support them. So how do you reinforce cardboard using press-fits?

One way I thought of was through building equilateral triangles out of scored cardboard, and placing them in-between two flat pieces of cardboard, to make one strong board. (See sketch below)

However, I realized this would take a ridiculous amount of cardboard to build. My next thought was to press-fit cardboard slats in-between two longer sheets of cardboard, but I realized that with the weight of the books, the slats would just fall flat. (See sketch below)

I then moved on to thinking about how to press-fit the cardboard using alternating outside braces places on each side. This seemed like the most promising idea of the three. (See sketch below)

Different cardboard reinforcement ideas

I didn’t want to test my limited knowledge of structural integrity, so I went for building a modular bookshelf, one that was based off of small cubes (like the bookshelf we have in the Lego Lab). I then started google-ing around for inspiration, and can across a wonderful bookshelf design from a French designer named Dany Gilles called the Stri-Cube, that allowed the cubes to be stacked to create a bookshelf of any dimension I wanted. (Image shown below.)

[Image source: www.danygilles.com]

Gilles was also using a similar approach to press-fitting cardboard that I had imagined, press-fitting large slats of cardboard into the frame of the bookshelf for stability.

I started by figuring out how Gilles made his cubes and reconstructing the cube in SolidWorks using the dimensions I wanted for my desk / my books. I then made modifications, such as adding in a semi-circle knob at the top that doubles as a handle and guide for stacking the cubes as I make more and an outside cover for the cube to hide the criss-cross of cardboard slats. Since Gilles seemed to make his cubes out of much thicker cardboard material, I made my press-fits rather large (1.5in cuts in the parts) and cut into both parts being fit together, in order to be as certain as possible that the press-fits would stay in place and provide structural integrity.

The following are some snapshots of my SolidWorks parts and assembly. I purposely picked a part that would be somewhat straightforward to construct, so that I could focus on re-discovering SolidWorks this week, remembering how to mirror parts, create correctly-defined sketches, and place part faces on drawings for print.

Box Assembly

Bookshelf Assembly

After SolidWorks-ing, I then went to print my parts. The first time I print, I accidentally print the entire box at a ratio of 1:2 – half the size I wanted. At this scale, the press-fits did not work, since the thickness of the cardboard was not cut in half, and I had to re-cut everything. The second time around, I cut the box correctly, minus a few issues with fiddling with the power on the laser cutter to make the laser cut all the way through the cardboard.

The slats that held the box together

Assembly of the box

Below are some pictures of the assembly and final product.

Isometric view of the box

Front view of the box

And the box now sitting on my desk :)

I didn’t want to print the cover or create another box, since it used up a bunch of cardboard and time on the laser cutter was in high demand. However, I hope to print more of these cubes and the covers and stack them to build a full bookshelf in the near future.