# Week 2: Lasercutting a press-fit construction kit (plus some vinyl-cutting fun)
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For the second week, we had two tasks: 1) use the lasercutter to make a press-fit construction kit from cardboard and 2) use the vinyl-cutter to do anything.
Files for download:
* K'nex pieces
* Aquila constellation laptop sticker
## Lasercutting: Cardboard K'nex
***Ideation:*** I thought about the project on and off for the better part of a week before I had an idea of what to do. A few things I had to keep in mind: a) Neil stipulated that the kit should be able to be constructed in different ways; b) my CADing skills are little more than rudimentary, even in 2D; and c) I wanted my project to be reasonably cool and innovative (in that a Google search doesn't yield a dozen examples). A memory of a toy construction kit from my childhood, Lego-like but with notches and sticks, coalesced in my mind, but I couldn’t attach a name to it. In a brush with serendipity, I happened upon a General Motors table set up outside the student center for Career Fair week, where a gaggle of students were playing with the very same toy kit that I was thinking of, whereupon the name hit me: K’nex! With that I could do a Google search for the foundation I needed for my press-fit kit.
***Design:*** I had decided earlier to use Fusion 360 as my go-to CAD software since Neil had said that it was a good fit for the class. Good fit though it might be, it still took me a torturous few hours to figure out how to do the most basic functions like move and rotate (you need to go into sketch editing mode, select all the components with the select tool - not clicking on the sketch, and setting the pivot point).
Given my struggles, I decided to stick with the basics of the K’nex kit: sticks and radial connectors.
I knew I wanted the full eight-notched connector (part 18), so I started by drawing an octagon with the circumscribe polygon tool. I then figured that it would be easiest to make the connectors by making a one-notch version from a 1/8 segment of the octagon, duplicating, rotating, and joining (which luckily can be done in Fusion by simply deleting the line between two adjoining sketches). Thus in principle the CADing was simple: take a 45 degree isosceles triangle, add a rectangle for the notch, and add angles to the notch to create wiggle-room (or chamfers: the details of that are on the class page). Simple in principle, alas, proved to be a slog in execution for the out of practice student of CAD. I kind of figured out how to use the parametric settings, but it didn’t prove particularly useful/necessary for this project.
Eventually, I was able to CAD this:
Which is not quite the same as the original K’nex, but close enough in spirit. On Monday night, I took my design to the EDS lab to print.
***Printing:*** Cardboard is a cool construction material because it bends and compresses while still presenting structural integrity. Unfortunately, cardboard pieces a) never come completely flat and b) are of varying thickness. I had designed my notch (4mm wide in design, ends up being around 4.32mm due to kerf loss) for cardboard thickness of about 4.3mm. I leafed through a couple cardboard pieces before I found one that was about the same thickness. I started with a small piece of cardboard to make a couple of trial pieces: one of each that I designed. I kept the defaults for the vector cutting, and got good results. I did discover that the skinnier “stick” piece I designed wasn’t strong enough, since it only spans one “ridge” between the top and bottom faces of the cardboard.
I ended up taping down the larger piece of cardboard I used for cutting out the rest of the pieces, because it was just way too warped. Taping the top edge down with paint tape worked pretty well. I did forget to check the size of my cardboard piece and had to abort my run because the laser was going off the bottom of the cardboard and onto the bed (yikes!), but I wound up with enough to build with anyway.
***Construction:*** The notches fit snugly but not too tightly to make taking apart a nuisance. I was able to make an abstract house:
and an abstract chicken:
One neat thing is that I could connect pieces even where there wasn’t a notch, albeit not very stably.
So I’d count this project as a success! Now, if only there was a way to get rid of the burnt cardboard smell and soot…
## Vinyl-cutting: Laptop Stickers Galore
***Ideation:*** I wanted to make something cool for my boyfriend and something cool for me. Unlike my boyfriend, who likes to surprise me with gifts, I took the logistically simpler route and straight up asked him what he would like as a laptop sticker. He picked Baroo, a cartoon pet yak character drawn by a Runescape player based on the game’s Pack Yak, a Summoning familiar.
For myself, I wanted to make use of the glowing apple on my MacBook Pro. I bounced around ideas until I alighted on designing a constellation sticker. The constellation figure would obscure all of the apple except where the stars would be cutout and oriented on the apple. Which constellation? My zodiac is Sagittarius, but that never meant very much to me. Instead I opted for Aquila, the eagle constellation: eagles have a lot of symbolic meaning in my favorite video game that I never actually played, Assassin’s Creed (many an hour nevertheless slipped away while I watched let’s play videos on Youtube). My favorite character from the series is Altair, the brightest star in the constellation; Aquila is the name of the ship in AC3; and Eagle Vision is the special power of the series protagonists.
***Design:*** Luckily, no CADing necessary for this! Google provided an ample supply of images, and vectorizer.io proved a free user-friendly and powerful tool to turn color images into black-and-white vector images. I used the “Clip Art: black and white” setting and played around with the grouping percentage and classification.
Baroo’s transformation:
Aquila:

Baroo I was able to cut directly, but Aquila needed some more processing. For that I turned to GIMP (which took an age to download). I got rid of the non-eagle bits with the select tool and the fill tool, and did a little touch up with the pencil tool. Then, in a different file, I opened up a Google image of the stars in the correct orientation. In a different layer of that file, I used the pencil tool’s star setting to mark where the stars were. I then copied that layer into a new layer in the eagle file and minimized it till it fit. To position the stars, I copied an Apple logo into a third layer to check to make sure the eagle covered the entire apple and that all the stars lay within the apple.

***Cut and Transfer:*** The white tape is a lot stickier than the blue tape, which made picking off the unwanted bits with the tweezers a little annoying. Unfortunately, the blue tape wasn’t wide enough for either of my stickers. Still, Baroo was easy enough:
Aquila, on the other hand, took a lot of measuring my laptop’s screen and apple logo and some ratio calculations to get the right size of. The final transfer was a painstaking process of hovering the sticker on top of the laptop in order to align it so that the light from the logo shone through all the stars but nowhere else.
Final product:
Next time, I should probably cut something easier to align.
## Addendum: Image Compression
Wow, that took a hell of a long time to compress all the images. A decently fast (though very manual) workflow I've worked out is to use GIMP.
1. Open the image in GIMP
2. Change the size so that the smaller dimension is around 300 pixels, depending on the resolution and importance of the image.
3. Export as .jpg, and use the slider to change the quality.
4. ***When referencing an image using html, make sure the quotes surrounding the file name are straight, else it won't work.***