Design

Although I had completed some initial design work with the sketches, it wasn't until I started modeling it in SketchUp that most of the major details coalesced. I had a chance to see the laser cutter in action at this point during a demo, and realized that perhaps two of its most powerful uses are its fine cutting ability and precision in drawing complex shapes. I decided I wanted the desk to incorporate a range of small to large pieces, varying in complexity. I also thought that building curves into the desk would be a good chance to try out the laser's unique capabilities in replicating the models I could create in software. I tried not to make the curves frivolous, instead incorporating them into the ergonomic design of the desk. On the bottom of the desk is a series of paneling and ribs which provide the main structural support for the top of the desk, and I drew a curve resembling a recurve bow and arrow into the bottom so that it would comfortably rest on the thighs. I also made a convex and concave front/back to the desk, which could allow it to fit more closely to the body in different settings.

I'll admit, the paneling along the concave and convex sides of the desk I felt particularly proud of. They are a series of interlocking plates that roughly follow the curving surface of the desktop, and interlock together with a series of tabs. The pieces are identical for the convex and concave sides, and the difference in the curve is achieved by inserting the tabs either in an interior or exterior facing direction.

One other feature I'd wanted to include from the beginning was expandability – ideally the desk would be small and portable, but I also wanted to be able to increase the work-surface when needed, for holding documents, a mouse, etc.

Below is a rough “timeline” of the modeling process, with my first square desk being at the far back (this was the desk I drew on the sketches above), and the final design in the front.

Cutting and first prototype

After I had my design completed, I went to the GSD to cut out the pieces. I ran a small test to see if the “buckles” I'd designed for a majority of the joints would function, and after finding them to be a little tight I expanded the slots they would insert into by 1/8 inch. After the pieces were assembled I went home to construct the kit. 

I encountered several difficulties in my building process. The buckle joints I'd designed were not nearly flexible enough to fit into the slots, and I had to push and jam them to make them fit, damaging the joints somewhat. Additionally, the slots for the extendable arms were too tight, and did not let the arms slide easily in and out, which made one of the major features of the desk inoperable. I thought perhaps that this was “good enough”, since it was Monday at this point. But after consideration I decided to make the time to redesign the model and try cutting it again.

Second prototype design

For the redesign, instead of utilizing a buckle design (which depends on flexibility in the material being used which corrugated fiberboard lacks), I designed a kind of interlocking slot and double-tab joint. Two pieces could be joined by inserting a notched tab on one into a slot on the other, and these were further secured with a small “plug” that inserts perpendicularly into the notched slot on the tab as well as the slot, securing both pieces together and making the joints tighter (the previous design was somewhat wobbly). I also expanded some of the slots to allow easier insertion of cardboard panels. Below are images of the final SketchUp design and assembly method.

Construction of final version

This time, assembly was much smoother, though not without issues. The new joint design worked for smaller pieces, but in order to insert the tab there needs to be wiggle room to angle the pieces against each other. For the larger pieces, I failed to consider the geometric constraints that would prevent the pieces from interacting at any angle but 90 degrees, and so I had to trim down the tabs  with scissors to make them fit. Assembly is certainly not “easy” for this desk, as it takes patience and persistence to get the pieces to align and insert correctly, which could hamper the usefulness of this design to amateur builders should they decide to make it.

Concluding thoughts

I got a lot out of this project, and I'm not just talking about being the proud owner of a cardboard desk. Designing this model pushed my abilities in SketchUp, which I haven't used seriously for about a year. I became reacquainted with the tools and process of design (I can't recommend SketchUp enough as an easy-to-use 3D “drawing pad”, which lets you easily translate ideas into practicable models in a simpler GUI than most other design software). Getting a chance to redesign and re-prototype my design was especially valuable. While the first desk was certainly usable, it was somewhat unstable and one of the major design features (the expandable wings) was inoperable.

A future redesign would fix the issues with the tabs that I needed to cut, and possibly incorporate more features and modularity into the desk. The geometry of assembly in particular is important. At many points in the building process, I realized there was no obvious “next step”, and often pieces needed to be jostled and flexed to fit into the desk.

There are also certain resolution constraints to be considered with the cardboard. At a certain size, any piece with an aspect that's thinner than the wavelength of the corrugation ridges in the fiberboard will lose significant structural integrity, because the corrugation will be effectively removed from the interior of the piece. This can be mitigated by aligning those cuts perpendicularly to the waves of the corrugations. But even then, there is a structural limit to how small a piece can be before it is too flimsy to provide support.

As a small aesthetic note, I would also be more consistent about the orientation of the corrugated fiberboard in the laser cutter – I've come to realize there is a “good” and “ugly” side to the cardboard, and my haphazard placement of the panels led to some of the external pieces having the smooth, good texture, while others have the rough, slightly corrugated side facing outward.

Despite integrating several curving surfaces into the desk, I believe it's construction (especially the inner core) to be very conventional. I think given the extreme versatility of the laser cutter, there is pretty much no design too complex to implement. In the future I'll be interested in seeing how I could incorporate non rectilinear structural elements into my models and designs.

Download the Sketchup schematics for your own use! These are Sketchup files, so you need to download sketchup (for free) and download the links, then open.

Download the flat rendering for cutting your own desk!

Final schematic and "exloded" view of desk, useful for assembly

This contains the timeline for my previous prototypes and designs.