A CNC flip disc display built by a maker known as Zimm takes a refreshingly unconventional approach to a notoriously fiddly problem: how do you drive hundreds of individual discs without hundreds of individual actuators? The answer, it turns out, is to not bother with per-disc actuators at all, and instead let a CNC tool head do the work, one disc at a time.
How the CNC Flip Disc Display Actually Works
Traditional flip disc displays rely on an electromagnet behind each disc, flipping it between two faces on command. That means a great deal of circuitry, a great deal of wiring, and a control system that has to address every single dot in the matrix independently. Zimm’s CNC flip disc display sidesteps all of that by using a single moving tool head that traverses the entire array mechanically, flipping only the discs that need changing.
The display itself is an array of 37 x 18 square discs, each black on one side and blue on the other. The tool head scans through that grid and uses a colour sensor and LIDAR to identify the current state of each disc and determine precisely how far to push it in order to flip it over. There are no magnets, no per-disc coils, no elaborate driver boards: just a CNC gantry doing the rounds with a fair degree of patience.
Speed is not this display’s strong suit, and Zimm makes no pretence otherwise. Flipping 666 discs one at a time, with sensing on each pass, is never going to be a real-time affair. What it is, though, is a perfectly workable system that produces clear, readable images from a mechanism of genuine elegance in its simplicity.
Drawing on the Display from Your Browser
One of the more appealing aspects of the project is that it is publicly accessible. The display, named PAR, can be drawn on or loaded with uploaded images directly from a browser, meaning anyone with an internet connection can queue up something to be rendered on the physical hardware. That kind of open interactivity gives the project a life well beyond Zimm’s workshop, turning it into something closer to a shared canvas.
The browser interface handles the image-to-disc translation, working out which of the 666 discs need to be in which state for a given image, and then the CNC mechanism gets on with the business of making it happen. Slowly, methodically, disc by disc.
More Plotter Than Display
The comparison that springs to mind most readily is not actually a flip disc display in the traditional sense. The mechanical, sequential nature of the tool head’s traversal across the grid brings to mind the world of pen plotters and CNC drawing machines, where a single actuator traces a path across a surface to build up an image over time. The logic is essentially the same: serialise the work, move through it systematically, and trust the mechanism.
Flip disc displays have a long history in public information boards, departure boards, and scoreboards, where their satisfying clatter and high visibility in bright light made them a practical choice long before LED panels took over. Zimm’s build honours that tradition while arriving at a completely different mechanical solution to the driving problem.
The LIDAR sensing element is a particularly considered touch. Rather than assuming the disc state matches what the software expects, the tool head reads the actual state of each disc before deciding whether to act. That closed-loop approach guards against errors accumulating across a full scan of the 37 x 18 grid, keeping the displayed image honest.
PAR is live and accepting submissions via browser now, which means the CNC flip disc display is out there working through its queue at whatever pace the gantry allows.
