🧵Week 16: Wild Card Week: Sewing
Project Heros
Final pants sewn up for robot:
The Plan
For wildcard week we wanted to do some sewing as both of our final projects would benefit from it. Sewing is a maker skill that is incredibly useful, yet is largely neglectled and my project has a great example of it. My rovbot currently has arms that need to be covered because: A. There is lots of wires that risk being caught on something and B. There are lots of pinch points in there. To 3d print or laser cut a part to protect this arm in its full range of motion is quite a design challenge, but a fabric sock to go over the whole arm is incredibly easy.
So thats what we will be making, 4 pairs of giant arm socks to make pants for the robot, and we will be cutting the material out on a laser cutter.
Test Run
I started by using onshape the design the pattern that we will cut out on the laser cutter. This was just a giant rectangle with some slots for buttons and the laser cutter seals the edge of the fabric as it cuts it so we were hoping that the seal on these button slots would give them strength.
Close up of the button slots (I dont know the correct terminology):
We will be cutting this on the Fab Lab's Trotec 360, so we booted up Ruby and Queued up the cut which took only a few seconds. Luckily someone has already been experimenting with cutting cotton and we used 10% power at 80% speed.
And this came out pretty well. Cutting fabric with a laser cutter was not a connection I made and it was suprising how precise it all came out.
And then I sewed the button on, and some elastic on the ends of it.
And here is the first test which came out well, but not perfect. The idea is that the elastic on the ends will hug the ends of the sock to the robot's joints, and the button will allow me to easily wrap it around the arm. The first issue is that it wasn't big enough. My first one was 630mm x 290mm and was sized for when the arm is in one position, but when I fully extended it to the other position, it would not longer fit so my next one was 100mm larger on both sides. If I was going bigger I would also be able to easily slide the sock onto the arm witout the need of buttons (the sock can be a sock and not a vest). This would also save me quite a bit of time as the buttons were the longest step of making a sock. The ends didn't properly seal as well and didn't fully cut through either - so next run I bumped it up to 15% power.
Making the Pants (But Good Now)
At this stage I was confident enough to make a proper sock. It was a little bit of a let down that my vector design had been reduced down to just a rectangle. So much so that I didnt even bother exporting a dxf from onshape and just drew a rectangle in ruby.
And this time with the upped power it cut through fantastically and seemed to do a much better job sealing the edge.
Once it was cut out, I folded and sewed the edges of the material to create a pocket to thread the elastic through. The elastic would then be strung tightly and sewn into place to make the ends of the sock scrunch together.
Then I looped it around and sew the other ends together to create a donut shape.
And after 4 more lots of this, they came out fantastically. The pants hid everything inside the arms and although it wont completely keep fingers out of pinch points, it does help a bit. It also greatly changes how to robot looks and feels visually, not only when its static, but when the legs actuate up and down they appear to do so by magic now that the mechanisms are hidden.
All in all I think this was a great wildcard week, I have sewn a handful of times before but with the ability to cut a pattern with a laser cutter, I think all my projects moving forward will see a lot more sewn parts. And when even complex patterns (not that mine turned out to be) can be cut in a matter of minutes, I think there is a lot of potential to make quite involved things.