Mark Rehost is a maker/engineer, community health worker, and a member of Milwaukee Makerspace. He is also, clearly, a fan of Frank Herbert’s epic Dune. This weekend at Maker Faire Milwaukee he’ll be showing his second generation sand table Arrakis following his original foray into complex patterning in sand, The Spice Must Flow, both of which create patterns worthy of sand worms.
Says Mark of his path to Arrakis: I was born an engineer and pursued engineering as a career from an early age. In high school, I was a member of ham radio Explorer Post 373 which met in the Bay View United Methodist Church, a few blocks from one of the Milwaukee Makerspace locations today. I eventually graduated from UW Milwaukee in 1981 with a degree in electrical engineering and embarked on a career that moved me to Illinois, California, Japan, and Texas. After 22 years at Motorola, Hewlett-Packard, Fujitsu Microelectronics, and Texas Instruments, corporate engineering and I had had enough of each other, and at 46 years old I decided to reinvent myself.Six years of school followed, and in 2011, at the tender age of 52 years, I graduated from the Arizona School of Dentistry and Oral Health. In 2012 I returned to the Milwaukee area to work in a community health clinic and promptly joined the Milwaukee Makerspace. For the last five years, I have worked at Vivent Health, an organization that cares for HIV patients.
Work always interfered with my home engineering projects, and when I became a dentist, working just four days per week freed up an extra day for projects. My first project at the Makerspace was designing and building a 3D printer that was much larger than the kits that were available at the time. Over the next few years, I designed and built two more printers and managed the 3D printing area at the Makerspace.
I used the knowledge of 3D printing mechanisms and electronics, gained at the Makerspace, to design and build my first sand table, The Spice Must Flow, for display at the 2018 MakerFaire Milwaukee. There were lots of 3D-printed parts in the mechanism. After that initial success, I wanted to reduce the noise, increase speed, and build the mechanism into a piece of furniture I could use in my living room. The Arrakis sand table that can be seen at MakerFaire Milwaukee this year is the result.
He describes how existing parts were used to create this unique artwork for Maker Faire Milwaukee 2018 in Hackday and in a detailed blog post that serves as a project template: This is a project that’s got a lot of off-the-shelf electronics and open source software to control the mechanism. Unlike most other sand tables you may have seen around the web, this one is powered by servomotors that allow insane speed and acceleration, operating at very low to low noise level, even at high speeds. The table uses a redesigned and 3D-printed corexy mechanism with sliding PTFE bearings to move a neodymium magnet that pulls a steel ball through a thin layer of sand, leaving behind interesting patterns. The patterns are lit from low angles by red and blue LED strips, lighting ridges red on one side and blue on the other, with dark shadows in the valleys between ridges.
The best way to get a feel for Rehost’s process from start to finish is to head over to his blog, in which he has detailed at great length his inspiration, design, technical steps, and the changes over successive iterations.
His first post describes building The Spice Must Flow for Maker Faire Milwaukee in 2018. These tables, like other CNC machines, use gcode files to control the motion of the ball that leaves tracks in the sand. He built a 28″ high table to hold the sand and patterns so that kids could engage. Check out the full process HERE.
His second post on The Spice Must Flow focused on the servo motors as a quiet and faster improvement to the patterning. He notes, “Stepper motors provide lots of low speed torque and high precision positioning without the need for closed loop control. Those characteristics make them great for machines like 3D printers because they don’t have to go too fast, they can deliver the precise positioning that 3D printing requires, and open loop drivers are cheap. Stepper motors operate in clicky detented motion, so they tend to vibrate and make noise. Better drivers can microstep them to get smoother motion.
A sand table isn’t a 3D printer. While it needs positional control, it doesn’t need the high precision positioning of a 3D printer because sand is a low resolution medium. What it needs is speed (well, mine does) and quiet operation more than resolution. I’ve been trying to make The Spice Must Flow sand table run both fast and quiet, neither of which are characteristic of stepper motors.
There is another type of motor that can deliver positioning control, speed, and quiet operation. They are called servomotors. Servomotors integrate a brushless motor (smooth and quiet operation) with an encoder to monitor shaft position and driver electronics to provide positioning control at high speeds.” READ MORE HERE.
This is part of the weirding way! With Arrakis, his 3rd iteration of the sand table, Rehost has gone smaller and lighter while maintaining the speed and performance of the servo motor upgrade. It also got a lovely fur coat. See a detailed description of the build HERE
Check out the full PLAYLIST OF ARRAKIS drawings. Or better yet, head over to Maker Faire Milwaukee this weekend to check out Arrakis in action.
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