Meetup report: 19 April 2018

Another successful maker evening! I was so busy that I forgot to take any photos, and I did not make a timelapse, so just a text report this week.

Tom brought his little walking robot, an updated version of Bob The Biped . Very nice little robot.

Stèph brought his Alphabot 2 robot, which he’s busy getting up and running. With some help from Tom, he managed to get it programmed, but there’s still some issues with the display etc, and he needs the correct batteries to get it to run.

Henré brought 2 projects: He has a nice electric guitar that needs some modifications, and he opened up his custom open source keyboard to see if there are any open pins on the controller that could be repurposed. Looks like there are 2 open digital pins, but not the hoped-for analogs. The guitar needs some routing to get the new parts in...

Li brought an old, rusted hand plane (Stanley 4, I think) and set about cleaning and restoring it. Some of the parts cleaned up nicely, but she still had a lot of work to do on the main body.

I got set up with the 3D printer, and made a print or 2. I had some trouble getting the prints to stick, as the bed height was not set up super-accurately. I tried some glue stick, and wow, that works. Had trouble getting the parts off the bed, even after it cooled down.

Reminders for next time: Take some photos!

Since next week Thursday is the last workday of the week, the next meetup will be in 2 weeks time.

Damping the swinging cutting wire in my vertical hot wire cutter

My 3D printer has a detachable x-y stage, which makes it very easy to create a hot wire cutter. In fact, that was the first thing I did when I got the x-y stage working. The cutter is very simple: I hang a rope from the roof, with the cutting wire (a steel guitar string) tied to it, and a 12V supply to heat up the guitar string. I added a weight at the bottom to keep the guitar string under tension and vertical. The x-y stage moves the wire horizontally in any shape I want, and I place the foam just below the x-y stage.

A video of this in action:

The only problem with this arrangement is that the wire swings back and forth when I move it, since it’s basically a heavy pendulum. These movements take a lot of time to die down, so I have to slow down the cutter a lot to avoid having wavy cut lines.

I thought that putting the weight in a tub of water would dampen the movement, but that is messy and does not provide great damping.

After seeing one of those videos with magnets falling slowly through a pipe, I had an idea: Why not use a magnetic eddy current brake?

The design is simple: I just attach a strong magnet (scavenged from an old harddrive) to the bottom of the hanging weight, and put a thick piece of aluminium below it on the floor. This works very well: Any swings in the weight is damped out within a few seconds, and it still allows the wire to move freely.

I uploaded a video of it here:

I’m really happy with the result. This means I now have a hot wire foam cutter added to my tools as well.