Open Source 3D Motion Platform with 50nm Precision

The ability to make precision mechanisms from 3D-printed, or at least partly-3D printed, components is a promising new field. Diffraction Limited's improved version uses a deceptively simple mechanism, similar to a delta robot, to achieve motion control down to 50nm, and with surprising speed.

This follows on from their previous flexure-based mechanism, using instead low-friction motion arms made from brass tubing and ball bearings. In contrast to projects such as OpenFlexure and RepRapMicron, 3D printing is only used to hold the precision parts in place.

Control is by means of conventional stepper motors driven as servos by a custom driver board based on the dual core Raspberry Pi Pico 2, using one core of the RP2350 to enable servo functions, and the other to manage the inverse kinematics required to calculate the positional vectors and velocities.

Feedback for the servo's position is provided by an ingenious array of neodymium magnets that are sensed with precision magnetic rotary encoder chips.

The (rather well-made) video below shows the build process, and demonstrates the device's ability to manipulate microchip dies and position optical fibers when driven with the project's own GCODE-based console app. They also plot the path of a segment of a "Benchy" model from the output of a 3D printer slicer.

With all of the software, original CAD files, and electronics done on open source platforms, it's a very adaptable project.