CONCEPT

I had a few different ideas for what to build for my construction kit. I thought about building something kinematic, such as a collection of pieces that could be stretched and compressed to form different shapes using a series of linkages. When I started SolidWork-ing, I ended up with a different design but one that still had movement. Using two different types of pieces, you can create numerous round objects that can roll around.

MODELING

SolidWork model of the kit

First, I modeled the construction kit in SolidWorks. Although I’ve used SolidWorks many times before, I had never gotten around to teaching myself how to use “global” variables. Since I wasn’t sure what material I would be using, I wanted to ensure that I could easily change the slot width and depth. To do this, I created variables using SolidWorks equations and linked smart dimensions to these variables. I then exported the variables, which exports as a text file. Finally, in my second part file, I imported the equations and linked the slot dimensions to the variables. When I adjust the dimensions in the text file and rebuild the parts in SolidWorks, the new dimensions are reflected in the design.

Exporting global variables in SolidWorks

LASER CUTTING

I created drawings of the two SolidWork part files and exported DXF files for each drawing. I then imported these DXF files to CorelDraw to send to the laser cutter. Unfortunately, even though I set a global variable in SolidWorks, I had to re-export the drawings each time I made a change, and then I would need to reimport the new drawing into CorelDraw. This was quite a tedious process, but I couldn't find a way to edit the file the way I wanted to in CorelDraw. Dropbox made this process a little easier.

Construction kit pieces

Since I wanted the kit to be able to roll around without coming apart, I chose sturdy ¼”-thick plywood that I found in the scrap pile in the Media Lab shop. I used a speed and power setting of 5 and 100, which I found from the list of speed and power settings that automatically opens up whenever you log into the laser cutter desktop.

It took a few tests to get the press fit just right. I ended up undersizing the slot width by 0.01” and setting a slot depth of 1/4".

Test cuts

ASSEMBLING

After cutting out enough pieces for one ball (6 connectors and 12 circular pieces), I cut out more to see what I could make with more pieces. I found that the kit is capable of forming a variety of round, roll-able designs.

Two joined spheres

Five joined hemispheres

Unfortunately, the wall thickness near the slot of the circular pieces is a bit thin, so the pieces break when handled roughly. If I were to make the kit again, I would increase the wall thickness.

Weak joint

And in case you were wondering, it does roll!

...and I'm currently using the spheres as a pencil holder!

Pencil Holder

DESIGN FILES

CAD files