If you go to a bar or restaurant, you’ll likely be given a disposable coaster on which to rest your drink. Though they might be interesting, and feature the establishment’s logo or another fun image, wouldn’t it be better if you could customize them on the fly? No, I’m not talking about doodling on them manually. Instead, try using one of these CNC coaster machines from Barton Dring!

Coasty the Coaster Toaster

In order to learn Grbl’s laser features, as well as produce something interesting to bring to a monthly hardware meetup, Dring decided to make a laser coaster engraver/cutter. He wanted a device that could fit inside a backpack, be powered via battery or USB, and “only scare the bar staff a little.”

What he came up with was a device that uses a 2-axis motion controller to feed a square coaster into a 3D-printed enclosure, and then either cut or engraves the desired pattern with a small laser. The x-axis goes back and forth on a normal overhead gantry system, while the y-axis is controlled instead by a stepper-controlled roller. This allows a user to insert the coaster through a slot in the side of the machine, which eventually spits out a nicely marked coaster.

The original version was entirely enclosed, which helps avoid laser exposure, but also means that you can’t see the process in action. To help with this, a window was added on a second version (seen in the video above). Dring is currently testing the design, and plans to release the source files, and even consider a kit, if all goes well.

Dring notes that:

The laser coasters take a couple minutes each. Most take less than 2 minutes. It is a perfect length. Someone asks what it is, I pop a coaster in, start the job and start explaining what is going. Just as my spiel ends, the coaster pops out. Etching takes about the same time, if not longer, for similar jobs.

Polar Coaster Marker

You may note that Coasty is meant for square coasters. What are you to do if your favorite establishment features only circular moisture absorbers? Dring has that situation covered as well with his polar coaster.

The device features a circular bed and a 156 tooth pulley. The coaster sits directly on this, held in place by six tabs around its edge. Rotation is controlled by a stepper motor via a belt that’s between the two.

A cantilevered arm is positioned above the bed, which is controlled by another stepper/pulley system. A 3D-printed part keeps a marking pen—used here instead of a laser—in place, and a servo motor is used as a simple Z-axis to lift the pen up or down. A compression spring assembly is also used in order to allow the pen to float slightly on uneven coasters.

Given its more “eye-friendly” nature, there is no protective enclosure around the device, allowing for easy viewing and maintenance.

As for why Dring built these two machines, he explains:

I am trying to make super small machines that spark conversation in social situations. They need to be portable and run off batteries. I also like to be forced to learn something with each project.

He’s quite happy with the results, and you can find the design files for the polar plotter in the blog post linked above. He is planning to optimize the laser assembly a little more before releasing the source files or considering whether or not to sell a kit. In the mean time, both of these look like great inspiration for other small CNC projects!