Key Findings
OpenCAL is the first open-source layerless 3D printer, designed to solidify complete parts inside a rotating vial of resin in about one minute. The machine can be constructed for roughly $1,600 in parts. To facilitate home building, Formlabs produces a dedicated photopolymer, OpenCAL Resin, which is sold in the United States via Prusa Research’s online store, Printed Solid, for $119.99 per 1 L bottle.
Technical Details
The system is based on Computed Axial Lithography (CAL). A projector sends calculated light patterns into a spinning vial of photosensitive resin; the object takes shape simultaneously wherever the light adds up, removing the need for a moving print head or support structures. The software inverts CT scan principles to calculate the projections required to build a physical object.
The OpenCAL V2 hardware consists of:
- A consumer LED projector and a Raspberry Pi 5.
- A stepper-driven vial mount within an aluminum extrusion frame and laser-cut acrylic panels.
- 3D printed components made from PETG, PLA, and TPU.
- Tomo, a free Windows application for STL conversion, built on the open-source Python library VAMToolbox.
Assembly takes one person five to six hours. The hardware is released under Prusa’s Open Community License (OCL 1.1), with software and firmware hosted on GitHub.
Background and Context
CAL was invented in 2017 at Professor Hayden Taylor’s lab at UC Berkeley and Lawrence Livermore National Laboratory (LLNL), with findings published in Science in 2019. The OpenCAL project was led by Taylor Waddell and contributed to by over 40 people over two years. Previously, CAL has been used for bioprinting, glass fabrication, and autonomous printing in microgravity via NASA-supported suborbital flights through the SpaceCAL program.
Significance and Outlook
OpenCAL aims to replicate the democratization seen with the RepRap project. The system is already being adopted by MIT, Purdue University, LLNLL, and NIST. A build workshop is scheduled for February 2027 alongside the VAM27@Berkeley symposium.
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