Today I went down to Menlo Park to use the CNC Plasma cutter at last.  I intended to cut a Shanty Town sign for the studio, but was told that the corrugated metal that I bought at Building Resources was galvanized steel which can be very toxic if melted due to chromium gas that is produced.  Think Erin Brockovich.  No thank you.  People were also a bit pessimistic about whether the machine could deal with the corrugation, so brain cancer aside, it probably wouldn’t have worked.

I did, however, cut my doll chain successfully!

This is 18 gauge mild steel.  Note the slight imperfections. This is due to the curve actually being non-contiguous in the software, so the cutter starts and stops repeatedly. Dealing with Corel Draw was quite a pain in the neck.  Initially I had lots of duplicate lines which were a mystery – turns out each line was actually a very skinny outline with a top and a bottom.  I then switched to Adobe Illustrator and had better luck, but still couldn’t get the vectors contiguous (if I spend another hour or two, I could probably figure it out.)  Another option would be to hack the G-code, but that would be a royal pain.

I put the metal on the roller to produce the above.  Turns out, with the slag (the extra melted goop that is produced), and width of the kerf (cutting beam), it’s slightly too small to fit around the bomb sight, and also slightly too high – I was careless on the height. This is what it looks like:

So I made another, this time with 7 figures instead of six as I found the six dolls a bit fat, and thought an odd number might look more interesting.  Here is what I cut:

I sandblasted this one and cleaned up a bit of the slag. I haven’t bent it yet since I am thinking about etching it first, and to do so I need it to be flat. I also want to figure out the rest of the mount before I commit to shaping it.

As it turns out, the machine was quite easy to use. It was the crappy software that held me up. All told, I spent around 5 hours to produce the above.  The machine itself is pretty quick, even with the superfluous stops and starts.  Take a look at a video of the Plasma cutter cutting the above.

While I was at TechShop, I also cut some vinyl to be used for the holder for the tank periscope.  Here it is, complete with transfer paper applied:

I got it to print properly the first time. Yay!  Spent about a half hour weeding it out, and for the most part had no issues.  Now I’m debating on whether to use it as a positive or a negative, and whether I want to etch or not with it. I could either use the vinyl itself as an acid resist, or I can use it as a stencil for some spray paint which would them become the positive.  I could also use that paint as an acid resist if I etch.

If I use thin copper, I can use the etchant as a cutting solution – if you leave it on a long time, it will essentially dissolve anything not masked, thus cutting out the letters.  This is a nice option for thin metal where the plasma cutter is overkill and sloppy.

I also have some questions in my head about how to best make the support itself. I don’t want to cover too much of the periscope as its metal is quite attractive.  Also, if I cut instead of etching, I’ll have to deal with stenciling issues.

Science!