About five years ago, “belt” 3D printers starting gaining traction. Instead of a conventional Y axis with a rigid bed, they have a conveyor belt. That enables infinite printing in the Y axis, so it is possible to print very long objects. Belt 3D printers are still pretty niche, but the utility is appealing. Unfortunately, most of them are still desktop-oriented and that limits the size of the objects in the X and Z axes. In order to print an entire full-size kayak, Ivan Miranda teamed up with Jón Schone to turn a treadmill into an oversized belt 3D printer.
A belt 3D printer is actually a bit more complicated than described in the introduction. The belt doesn’t replace the Y axis entirely, but rather acts in concert with what would normally be the X and Z axes to print at an angle (usually 45 degrees). That angle is important, because it lets the machine finish an entire layer on top of the belt. Otherwise, the whole part (which could be several feet long) would need to move off of and back on to the belt with every layer — ruining adhesion to the belt.
In this case, Miranda and Schone had to replicate that geometry on the treadmill. The finished printer still looks a lot like a treadmill, which is intentional. But a lot of custom fabrication went into the design in order to achieve the proper geometry. The Z axis, for example, is made of custom steel uprights with heavy duty linear rails. The X axis gantry is also custom and has a beefy linear rail of its own.
That is a lot of weight to move around, so the printer has large, powerful stepper motors. Miranda even had PCBWay mill custom heat sinks to help keep the motors cool, which was important to stop them from melting their 3D-printed mounting brackets. Even the extruder was scaled-up to huge proportions, giving it the ability to push the ridiculous amount of filament necessary to form a kayak through a 1mm nozzle.
To control it all, they used a Duet 3 Main Board paired with a Duet 3 Tool Board. The latter is on the extruder carriage and communicates with the former through a CAN-FD connection, reducing the number of wires going to the extruder.
There were, predictably, lots of challenges to overcome. But Miranda and Schone were successful in the end. The treadmill 3D printer worked and they launched the kayak at Maker Faire Prague earlier this month.