--- title: "A resin vial and projector make volumetric 3D printing buildable" locale: "en" url: "https://irz.fr/en/articles/opencal-volumetric-printing-en" markdown_url: "https://irz.fr/en/articles/opencal-volumetric-printing-en.md" category: "craft" tags: ["3D printing", "fabrication", "open source", "resin", "makers"] published_at: "2026-08-11T12:05:00.000Z" author: "Camille Morel" translation: "https://irz.fr/fr/articles/opencal-impression-volumetrique-fr.md" --- # A resin vial and projector make volumetric 3D printing buildable No layers, no supports: OpenCAL projects images into a spinning vial of resin and the whole part appears in minutes. A volumetric printer you can build from a Raspberry Pi 5 and a projector. # OpenCAL brings volumetric 3D printing out of the lab There is a scene science-fiction fans will recognise instantly: a vial spins, a light flickers, and a whole part materialises inside the liquid. No layer built up one weak line at a time. No support structure to carve away. The object is simply there, complete.[3](https://hackaday.com/2026/06/14/opencal-computed-axial-lithographic-3d-printing-for-everyone/) That machine has left the laboratories. OpenCAL, an open-source project from the UC Berkeley Design for Nanomanufacturing group, documents in detail a CAL printer — Computed Axial Lithography — built from ordinary components and a Raspberry Pi 5.[1](https://github.com/computed-axial-lithography/OpenCAL) [2](https://opencal-org.readthedocs.io/) [5](https://design-nano.berkeley.edu/) ## The scanner reversed The technique borrows a principle from medicine: tomography. In a CT scan, X-rays pass through the body to reconstruct a volume. CAL does the reverse: from a 3D model, software computes a sequence of projected images which, crossing a spinning vial of resin, accumulate a light dose exactly where the part must form. The part solidifies in one block while the rest of the resin stays liquid.[2](https://opencal-org.readthedocs.io/) The result: objects a few centimetres across printed in minutes, with no layers, no supports, no peel-off from the build plate.[3](https://hackaday.com/2026/06/14/opencal-computed-axial-lithographic-3d-printing-for-everyone/) [4](https://makezine.com/projects/instant-prints-opencal-layerless-3d-printing/) The core software is VAMToolbox, a volumetric tomography tool that generates the print files the machine consumes.[2](https://opencal-org.readthedocs.io/) ## Built in an afternoon What makes OpenCAL remarkable is not just the technique, but the way it reduces the gesture to accessible parts. The firmware runs on a Raspberry Pi 5 (2 GB RAM or more), controlled through a 20×4 LCD and a rotary encoder — so no attached screen is needed to run a print.[1](https://github.com/computed-axial-lithography/OpenCAL) [4](https://makezine.com/projects/instant-prints-opencal-layerless-3d-printing/) The hardware list asks for a compact DLP projector and a Fresnel lens, a stepper motor driven by a Pololu Tic T249, a Pi Cam to record the process, and parts printed on an ordinary FFF printer. The physical files and bill of materials are published.[1](https://github.com/computed-axial-lithography/OpenCAL) [4](https://makezine.com/projects/instant-prints-opencal-layerless-3d-printing/) And here is the detail that changes the experience: printing plays like a video. Print files are MP4s, projected by mpv while the vial spins, and the machine reads the rotation speed directly from the filename.[1](https://github.com/computed-axial-lithography/OpenCAL) ## The remaining constraints The project says it plainly: this is in active development, and the resin is the real barrier. CAL chemistry is demanding — it needs a viscous resin, transparent enough at the curing wavelength, with a non-linear response so it cures only where the accumulated dose is high enough. Part of the tuning starts with chemistry, not code.[2](https://opencal-org.readthedocs.io/) [4](https://makezine.com/projects/instant-prints-opencal-layerless-3d-printing/) Surface quality is closer to an older SLA than to a polished shop part. And for now the machine will mostly print volumes of a few centimetres, though larger formats have been attempted.[3](https://hackaday.com/2026/06/14/opencal-computed-axial-lithographic-3d-printing-for-everyone/) ## The lab opens up OpenCAL is not the first machine of its kind: CAL dates to 2019, and lab volumetric printers stayed beyond a hobbyist's reach. What has changed is the whole package: open-source software, reproducible hardware, end-to-end documentation, and a Discord community so you are not alone in front of your build.[2](https://opencal-org.readthedocs.io/) [4](https://makezine.com/projects/instant-prints-opencal-layerless-3d-printing/) It is the same movement as RepRap for extrusion printing: making a fabrication technology reproducible at personal-workshop scale, so others do not just use it but improve it.[4](https://makezine.com/projects/instant-prints-opencal-layerless-3d-printing/) The lesson for a maker is not “print objects without layers”. It is: even a process born from medical research becomes tinkerable material as soon as someone publishes the files, the plans and the chemistry. The next OpenCAL may not have to come from a laboratory. ## References 1. [OpenCAL — GitHub repository (computed-axial-lithography)](https://github.com/computed-axial-lithography/OpenCAL) 2. [OpenCAL — official documentation](https://opencal-org.readthedocs.io/) 3. [Hackaday, OpenCAL: Computed Axial Lithographic 3D Printing For Everyone (2026)](https://hackaday.com/2026/06/14/opencal-computed-axial-lithographic-3d-printing-for-everyone/) 4. [Make:, Instant Prints! OpenCAL Layerless 3D Printing (2026)](https://makezine.com/projects/instant-prints-opencal-layerless-3d-printing/) 5. [UC Berkeley Design for Nanomanufacturing — OpenCAL](https://design-nano.berkeley.edu/)