Motion Machine Overview:

This machine was one of three parts in an exhibit built to convey aspects of circuits as they relate to STEM applications. I was responsible for the design, assembly, and coding of the prototype’s firmware and hardware, as well as iteration and construction of the final machine.

Component Selection

The powder, ball bearing, and magnet were critical to the consistent performance of the machine. A powder too varied in particle size would sometimes knock the ball out of the magnetic field. A bearing too large would have too much friction for the magnet to overcome. A bearing too small would not push the powder out of the way. The magnet needed to be strong enough to pull the bearing through the power with a 0.375 inch gap, but not be influenced by the steel linear rods. Shuffleboard powder makes an excellent powder due to the ultra low friction and eye-catching translucence.

Unexpected Challenge

A surprising challenge was ensuring smooth travel of the ball-bearing. Every single surface imperfection in the basin telegraphed  through to the ball. The ball would also roll to either side of a granule larger than 0.25mm. There was also a lot of backlash in the ball’s movement during quick changes in direction or speed. The solution was to include a neoprene mat in the basin. Initially resolved with a mouse-pad, the rubbery mat provides a uniform surface. There is a sponginess to the material that allows a granule that would previously cause the ball to move laterally to instead be pushed into the mat while the ball passes over it. The mat also increases the friction enough that backlash is reduced.

Visual Design

I wanted to make the entire workings of the machine transparent figuratively and literally. The clear cast acrylic plates leave nothing to be obscured. While a belt driven system has less precision and lower load capacity than a leadscrew drive system, this machine would not be used for precision or heavy weight tasks. By mounting the motor along the belt, the relationship between component and action is more visible. LEDs were added to the top and bottom to provide contrasting highlights and shadows to the otherwise monochromatic machine.