The Art Of Motion Control

A trip to the Exploratorium, as Visiting Artist, 3/2-16, 2003:

I was invited to spend two weeks at my favorite place in the world (no exaggeration). This is a quick posting of some of the things I got a chance to work on, and the wonderful people I worked with.

The view, upon arrival.


"Sisyphus West:"

One of the first things I set to work on was the construction of a sand plotter, identical to the one I have at the Science Museum of Minnesota. I had shipped the electromechanical guts, but had to improvise the frame from available construction lumber:

Since fine garnet sand is used in many of the Exploratorium exhibits, I grabbed some and tried it. An interesting (and in my view, unwelcome) feature is that it is contaminated with iron:

We tried it on the floor, and although a few visitors could not resist touching the sand, it survived reasonably well. Prior to my departure, Karen and Mike helped me move it into the Production Studio (a small building housed within the exhibit space), where Sisyphus' daily toil will be visible to visitors through a window:


CNC routing:

A few days into my stay, I had the opportunity to give an informal talk to the staff, during lunch. After the "brown bag" (in which I showed images from my site) some of the staff who work at "Exhibit Services" (where Exploratorium exhibits are built for "export" to other science museums) invited me to look at their new CNC router table. After seeing the rig (3 axis, servo driven, 4' x 8' capacity) I asked for permission to see if I could generate true 3D tool paths for it. They had not yet tried this, since most of the time they are cutting 2D paths in panels. Instead of the usual "well, maybe" or just plain "no" -- they said "sure!" The next day I had a test path ready. With lots of help from a very cool group of staff we succeeded in showing that it works:

A few days later, after writing more elaborate LISP routines in AutoCAD, we were able to cut this surface (32"x32"):

I could happily spend two weeks just doing this!


Emu egg engraving:

One of my favorite demonstrations of do-it-yourself CNC involves plotting on eggs. I shipped out one of my high-resolution "ovagraphs" and was plotting on chicken eggs within two days of my arrival. But I had never attached a Dremel to this machine, and figured this was a good time to try it. I had bought three emu eggs on eBay ($5 a piece) and thought that the natural dark green surface would be perfect. I quickly attached a flexible shaft to the Dremel, and affixed it to my "pen axis." It took some coaxing to get an acceptable pen up/down response, but eventually I decided to just go for it:


Do-it-yourself CNC heaven:

Several months prior to the trip, as I was thinking of the activities I might want to try, one that I favored was to build a large XY table for the shop's plasma torch. But no one seemed especially interested in this (and some were perhaps a bit hostile to the idea). And so I tucked this fantasy away in the "hopefully someday" heap (already pretty crowded). But while I was doing one of my favorite things-- junk hunting-- I discovered an unbelievable cache of high quality linear motion components in various Exploratorium storage areas. This was made all the more amazing by the truly surreal space known as "the rotunda." The Exploratorium resides in the remnants of buildings built in 1915 for the Panama-Pacific International Exposition. Called "The Palace of Fine Arts," it looks like a Greco-Roman Temple:

The Exploratorium stores materials in a few of the "legs" of this domed structure. Here, Charles (one of the talented exhibit developers at the Exploratorium) is opening up a "leg," and the view inside:

After retrieving some choice components, and swapping out the servo motors for steppers (also found in the rotunda), Charles and I were able to construct a 3-axis table, with usable travels of ~4'x5' with 3" of Z:

Not bad for one day's work! It will be fun to see what the Explo staff does with this thing.


Although I was in perhaps the most beautiful city on earth, there was not much time to get out. Karen and Mike, two wonderful educators at the Exploratorium and the people responsible for arranging my trip, invited me to their home in Napa during the middle Sunday of my trip. Charles and his wife Dena drove me up and we went for a great hike:

To Karen, Mike, Charles, Dena, and all the phenomenal staff I met and got a chance to share ideas with at the Exploratorium-- I can't thank you enough.

-->Karen and Mike's scrapbook about my visit