Vik Olliver has added a UV print head to RepRapMicron, his open source micron scale RepRap, that cures resin through an ordinary fibre optic patch cord.
RepRapMicron, or μRepRap, aims to bring micron scale fabrication to the masses the way RepRap did for desktop printing. Its PIKA machine, the current recommended build, has so far printed with a fine probe that picks up UV nail gel by capillary action and sets it down as tiny droplets. Light was never the main plan, because optical methods stop scaling below the wavelength a typical workshop can reach. Curing resin in place with UV is still a quick way to build structures with members tens or hundreds of micrometres a side, which would be tedious with the probe alone.
In μRepRap tradition the head uses standard commercial parts. Light from a small UV LED module, the kind found inside hobby gooseneck USB UV lamps, travels down a single mode network patch cord that Olliver turned from a duplex into a simplex cable with a hacksaw. A printed adaptor keeps the LED lined up with the fibre, a printed holder mounts the fibre on the Z axis where the probe normally sits, and the controller’s coolant mist output switches the light on and off through a resistor in a screw terminal block.
A small Python filter takes GCODE from PrusaSlicer and, since there is no extruder, turns the UV on whenever a move would have extruded and off when it would not. PrusaSlicer will not accept a nozzle that fine, so models are sliced with each millimetre standing in for 10μm and the filter converts the result into microns for the GRBL controller.
Printing is a hands on job. The fibre is lowered until it touches a Kapton taped glass slide, then backed off 5μm to set zero. A droplet of standard 3D printer resin goes in with a needle and surface tension does the rest. The soft part is then washed in isopropyl alcohol and given a final UV cure. The fibre end needs cleaning after every run, otherwise a film of cured resin builds up and prints turn into puddles.
The UV head files went up on GitHub in early October 2026, and the wiki page documenting the build was last updated on October 18. Early results include a tiny “Hello, World” and a 100μm square set in resin, and the project now lists cured lines just 9μm wide.
The idea builds on work by Diffraction Limited, whose MicroManipulatorStepper used a UV laser and a 4μm fibre to print micron scale objects. For μRepRap, though, the fibre is a fast way to lay down bulk material, with fine detail added later by probe deposition.
The head is released under the GPL, with sources on GitHub and pre-built STLs on Printables. The wiki page is still marked as under construction and carries a warning in true RepRap spirit, “Do not look into UV source with remaining eye.”
Source: RepRapMicron wiki on GitHub
