Prompt: Create a cardboard construction kit

The assignment for this week was to create a press-fit cardboard construction kit. Skills learned included laser cutting, measuring kerf, and parametric design. My goal for this week was to create a press-together kit with a joint.

The problem with a laser cutter or other removal tool is that there is extra material which is removed around the cut area, and the extent of that material depends on many factors such as cut speed, cut power, and the actual materials used. In this assignment, I measured the width of the kerf left by a laser cutter in cardboard, and utilized that measurement in a design of a joint. This measurement was used in inkscape to change the design of the joint so that the joint fit together without adhesives.

Video of snake moving:

The snake was made up of a series of joints. The alternating pattern of the joint enabled the snake to rotate in 2 orthogonal directions. Each joint was made in inkscape, and looked like this:

The head of this joint fits into the tail of the next joint piece. The two antennas at the bottom enable the bottom half to wiggle open while it is being fit onto the next piece. Inkscape allows you to clone parts, and these cloned parts will change shape along with the master. Thus, by changing the master, it is possible to propagate changes along the whole design.

This design, however, is created through a series of boolean operations, including intersection, difference, and unions. Due to these operations, there is a step-by-step process of generating a design after the kerf size is found. In the future, a more coding-based modelling tool can provide a more automated way of building the design.

Master elements in the design:

The kerf was measured by cutting a square out of the cardboard. The kerf width was found by subtracting the widht of the square from the width of the hole and dividing by 2.

Width of square (in): .9835

Width of hole (in): 1.010

kerf = .01325 (in)

Cardboard thickness (in): .1525

Width of features in inkscape (in): 0.126

Measuring the kerf

When the Kerf was fully measured, I did a test fit of a basic snap-together piece in cardboard. These fit together too snugly, so I increased the feature size by 0.001 inches to 0.127 in.

Building a test-fit

Once that was complete, I moved on to creating my first set of joints. The result was that the joints held together for a little bit, but after a few motions, they fell apart. This was due to the kerf coming close to the edge of the joint features. This was rectified by scaling the joint.

Testing the first joint

After scaling the joint, it was replicated 60 times. This would make up the construction kit:

Cutting a series of joints

Failure case:

Here we can see that if the nub at the tail of the joing is not wide enough, it is not sturdy enough to sustain many assemblies and breaks apart. This was rectified in the design by increasing the width.

Final assembly of the snake!

Vinyl Cut Piece:

For the vinyl cut piece, I cut out a character from the Legend of Korra. I didn’t put on proper backing, but it was enough to be able to put the vinyl on the white board in my office: