week 2: computer-controlled cutting
Prior Experience: 4/5
I have used the vinyl cutter before to score sheets of paper for origami, using the Cricut in Edgerton, but never to cut anything. I also have used the laser cutter before to cut/engrave presents for my friends/make random small things for myself, and I also have used laser cut acrylic for a research project in the past. I am pretty familiar with the laser cutter and how it works; my main limitation this week is my CAD/design abilities, not my familiarity with the laser cutter.
This week's assignment had two parts:
- cut something on the vinylcutter
- a) characterize your lasercutter's focus, power, speed, rate, kerf, joint clearance and types
b) design, lasercut, and document a parametric construction kit,
accounting for the lasercutter kerf, which can be assembled in multiple ways
Vinyl Cutting
My iPad has a clear case with no decoration, so I decided to vinyl cut a small sticker to put on it. I found an image online of the Pixar man, set the resolution to 300dpi, and then put it through the CBA mods (http://mods.cba.mit.edu/?program=programs/machines/Epilog/cut%20png) to set up the parameters for the vinyl cutter.
I sent it off to the vinyl cutter and it did all the work for me!
Then, I transferred the sticker (sticky side up) onto a small piece of transfer paper, and then stuck it onto the back of my iPad. Choosing an image with thin lines made it annoying to transfer, and I lost some of the lines, but it turned out okay.
(Sorry it's upside down...)
Laser Cutting
I made a modular origami-inspired lamp that can be assembled into different polyhedra.
Sketches
The assignment was to design a parametric construction kit with multiple ways of assembly. In modular origami, there are units consisting of squares that fold on the diagonal, plus flaps to join them together, that can be assembled in lots of ways. In particular, 6 units makes a cube, 12 makes a stellated octahedron, and 30 makes a stellated dodecahedron!
(This is a random image I found on Google that illustrates this concept.)
I also saw previous projects for laser cut lamps, which can only be assembled (basically) in one way. I wanted to extend this idea by making base units for such a lamp that can assemble into various possible lamp shapes. Different designs can be put on the faces of each base unit.
(lamp inspiration that I found from googling "laser cut lamp")
I sketched out the concept on my iPad to make sure it would actually work out.
(Here is the initial idea.)
(I realized that if each "unit" was a square, then the connections between each unit could be at 90 degrees, and the hinge along the diagonal provides additional degrees of freedom for which angle the units connect with.)
I ended up with this simple design for the square units and joints, and I also drew some possible designs for the faces of the units.
Laser Cutter Specifications
Joint Testing
The corrugated cardboard is 3/16", which is .1875. I tested potential widths of joints by cutting out 0.12, 0.13, 0.14, 0.15, 0.16, and 0.17 width joints on a scarp piece of corrugated cardboard. (The kerf is around 0.02 in, so I cut the joints smaller to account for it.)
I don't know how to CAD or use Rhino so it took forever to CAD it.
For the first test, I cut it on the laser cutter, using the specifications that were written down for corrugated cardboard (30 speed, 18 power, 500 frequency), but the laser didn't cut all the way through. For the second test, I used 30 speed, 22 power, 500 frequency, but it still didn't cut through. For the third test (pictured below), I used 25 speed, 25 power, 500 frequency, which worked.
Results: I found that 0.12 - 0.13in was an optimal width for the joints.
Score Testing
My original idea was to use flexures to bend the cardboard, but I realized that it would be much easier to just score the cardboard so that only one side is cut, so that the cardboard can bend along the hinge created.
I tested the specifications for the laser cutter, based on the reference specifications of 30 speed, 5 power, 500 frequency. I found that below 15 power, the cardboard did not get cut through to the bottom layer. I decided to use 30/15/500.
Prototype
I designed my first attempt using Rhino non-parametrically.
I cut a prototype, just two 3in x 3in squares and a connector, using a joint width of 0.12in. I cut the squares with 25 speed/30 power/500freq, which I found to be optimal. The folds were cut with 30/15/500.
It worked pretty well! The joints were a little hard to connect, and ended up squishing. I decided to increase the size to .13 as well as chamfer them.
Prototype 2
I wanted to make sure that my idea would actually work, so I cut out 12 units to make an octahedron.
I am quite happy that it does work! For the next iteration, I wanted to chamfer the joints, cut out a design on the faces, make the CAD parametric, and I chamfer joints, cut out design on body, and adjust some dimensions.
Parametric CAD
I couldn't figure out parametric design in Rhino (which is the software on the computers in my shop), so I did it in Fusion 360 and exported it to Rhino.
I drew a geometric sunburst design, inspired by stained glass windows, on the face of each right triangle.
Attempt 3
This is the final version.
I did a small initial test with joint width 0.13, but it was a little tight/difficult to assemble so (using my parametric design!) I increased it to 0.14, which was perfect!
I made a cube and a stellated icosahedron.
It took so long to assemble the lamp but it was worth it.
(The lamp makes cool patterns when it's dark.)