Week 1: Computer-Controlled Cutting

This week, we took a look at using both the laser cutter and the vinyl cutter. After being trained on both machines, I took my CAD designs from the previous week and set myself to cut a ukulele using the laser cutter. Even though I had initially planed to make the ukulele modulable in such a way that it could be turned into a steel guitar, time constraints (and very amateur skills) meant that I was only able to cut the ukulele parts, and only one neck, but I did learn a lot from the experience (cf. my pictures later down this blog post)

I had stopped my design after making my assembly, so I had to continue my design by designing individual pieces. To do so, I extracted all faces of my design and padded them individually with a thickness of 3mm, which is approximately what I expected to have with 1/8'' thick cardboard. I paid attention to pad the lateral faces in reverse in order for them to be able to be assembled with the top and bottom pieces later on. I then used the Laser Cutting addon from FreeCAD to design press-fit joints to unite all of the pieces. I used a kerf setting of 0.14mm, that I gathered from exchanging with my classmates and the TAs.

Then, I used FreeCAD Technical Drawing workbench to draw an individual view of each of my 26 pieces. This required me to rotate a few pieces around the Z axis, so that they would be flat in the direction of the X axis. I exported every drawing onto an SVG file, and then it was time to use the laser cutter!

I imported all my pieces onto CorelDraw, and started to realise that the design was bigger than expected, but I'm not quite sure why. I went ahead and distributed all the pieces onto 3 sheets in CorelDraw. After discussing with my classmates (shoutout to Alan), I decided to use double corrugated cardboard in order for the strings not to bend the body of the guitar. I cut the first pieces and realized that the added thickness to the cardboard meant that I had to use other parameters for the laser cutter than the default ones. My first sheet of cardboard was not cut through at all, and I had to do a second pass. I measured the second sheet of cardboard and obtained a thickness of 1/4'', which led me to use half of the speed I used, so 1.4. This worked much better on the two other sheets of cardboard I used. Oh, and I had to use the hand cutter to finish cutting some pieces cut with the first settings.

By this point, it looked my ukulele was actually going to be a full sized guitar. I then had to assemble my 26 pieces into the guitar. Some press-fit joints worked perfectly, but others less so. I had to use a hammer to hammer some pieces in (thanks cardboard for your flexibility and forgiveness) and secure the assembly. This started to look good and got me excited.

I then used a set of 4 ukulele strings that I bought earlier to try and actually string my guitar-shaped ukulele. I pierced small holes through the bottom of the guitar and let my strings pass through. For the pegs, I had to cut an opening at the bottom of the head of the fretboard, and pierce some holes. This turned out pretty good, but the pegs I had bought were a bit wobbly, so I had to use extra cardboard to add some thickness to the initial layer of cardboard, just where the pegs are.

Finally, I tuned the ukulele-guitar and it turned out to be pretty good (proof on picture below)! A major problem is that the cheap pegs that I got kept turning by themselves and getting out of tune, probably because the cardboard cannot support the pressure as well as wood would. Anyway, it was a great experience and I definitely learned a lot from it. I finally compared my wannabe-ukulele to a real ukulele, as well as to a real guitar, and the difference in sizes was pretty fun for me to see. I definitely need to pay more attention to how sizes on the CAD software translate to sizes in the cutter in the future.

I additionally decided to design a few vinyl stickers inspired by album covers, which was really fun. Below is my sticker for Taylor Swift's Midnights album. It had a lot of very small features which made it hard to properly weed without damages, but I managed to only lose one of them (apologies Taytay for your nose bridge)

Notes to a future me (learning outcomes):

Spend less time on CAD and more time on the cutting, it will help you see what's feasible and what's too ambitious.
Check the actual size of your carboard surface before starting cutting.
Take more time to figure out the best kerf settings for your press-fit joints to work best.
Don't make too many small features for the vinyl cutter, you'll hate yourself.