The vast majority of 3D printers utilize a Cartesian layout, meaning that they move linearly in the X, Y, and Z axes. From a conceptual standpoint, that’s the simplest layout. But that doesn’t necessarily mean it’s the best for every situation. Delta 3D printers, for example, are somewhat popular thanks to their high printing speed, which is a result of the low weight of the moving parts. Many other layouts are possible as well, each with their own pros and cons. Pontus Borg's five bar parallel arm SCARA robot, for example, is capable of printing at incredible speeds.
A SCARA (Selective Compliance Assembly Robot Arm) is a specific kind of robot that is defined by its rigidity in the Z and axis and speedy movement in the X and Y axes. All of the joints pivot on the XY plane, and only the base moves up and down in the Z axis. This particular robot design works in the same way, but with linkages between the XY motors and the end effector where plastic is extruded. By pivoting the first two arms of in the linkages, the exact position of the hot end can be set in the XY plane. Movement in the Z axis is similar to a conventional 3D printer, and is provided by a lead screw.
The primary advantage of this design is that it can print very quickly—up to 300mm/s and with an acceleration rate of 12,000 mm/s^2. The quality isn’t amazing at those speeds, but is quite good at around 120mm/s, which is still faster than most Cartesian FFF (Fused Filament Fabrication) 3D printers. The controller board being used for this 3D printer is a Duet3D, which has a powerful 32-bit 120MHz ARM Cortex-M4 microcontroller. The Duet3D has official support for SCARA 3D printers, but this unusual parallel arm design required custom firmware. For most people, the benefits of a build like this aren’t worth the challenges. But it is still fantastic to see people experimenting with unconventional 3D printer designs.