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OPENCAL: AN OPEN-SOURCE VOLUMETRIC 3D PRINTER THAT CURES A WHOLE OBJECT AT ONCE, NO LAYERS

A 3D printer that cures the entire object at once inside a rotating vial of resin, no layers, no supports, and the complete build is published.

by Computed Axial Lithography group at UC Berkeley

FULL CAD BOM FIRMWARE DOCS

WorkshopOpen-hardware

Built withRaspberry Pi3D printing

difficulty
●●●●○
time
a weekend-plus
license
UC Regents (software), OCL v1.1 + GAtt + RnD (hardware)
repo
repo ACTIVE542 stars

WHAT YOU’LL NEED

Videos
1
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COMPAREE VERDICT

OpenCAL is computed axial lithography: a projector throws computed light patterns into a slowly rotating glass vial of photopolymer, and the accumulated dose solidifies the entire part at once. Inch-scale parts form in minutes rather than hours, the part is suspended in liquid the whole time so no support structures are needed, and the surface is smooth. The documentation is genuinely complete — CAD, a BOM of about 1,638 dollars, step-by-step guides, a ready-made Raspberry Pi image, and the team states assembly takes an afternoon once parts are gathered and printed. This is a Berkeley research group publishing an accessible version of the technique they invented in 2017. The build uses a Raspberry Pi 5, a Pololu Tic stepper controller, a NEMA 17, an 8x8 RGBW LED array, a 20x4 LCD with rotary encoder, a Pi Camera Module 3, laser-cut acrylic and 3D-printed parts, and any HDMI projector (tested with NexiGo Nova Mini). The resin is manufactured to specification and sold ready-mixed. The licence is non-commercial for end users; if you want to sell prints or machines, you need separate permission. The single thing most likely to go wrong is underestimating the optical alignment — this is a research instrument you are building from scratch, and the projector-to-vial path has to be precise or the dose accumulation will be off and prints will fail. If you want to see volumetric printing work and you are comfortable with research-grade hardware, this is the complete build.

GOOD TO KNOW

  • —Complete documentation at opencal-org.readthedocs.io: CAD files, bill of materials totalling approximately 1,638 dollars as of June 2026, step-by-step guides for frame, optics, rotation, electronics, assembly and wiring.
  • —Pre-built Raspberry Pi 5 image provided so the machine boots straight into the control software.
  • —Hardware and design files under Open Community License OCL v1.1 with General Attribution and Research & Development add-ons: free for non-commercial end users to use, copy, modify and repair; commercial use requires separate arrangement.
  • —Software under UC Regents licence, free for non-commercial use only.
  • —Resin is a UDMA-based photopolymer manufactured by Formlabs to the OpenCAL formulation and distributed by MatterHackers, so no chemistry mixing is required.
  • —Print files generated with VAMToolbox (computes tomographic projections) and prepared with Tomo.

Parts to buy

12 items

From our check of the build. Exact quantities and part numbers are in the creator’s BOM.

  • Raspberry Pi 5Find
  • Pololu Tic T249 stepper controllerFind
  • NEMA 17Find
  • 8x8 SK6812 RGBW LED arrayFind
  • 20x4 I2C LCDFind
  • Rotary encoderFind
  • Pi Camera Module 3Find
  • HDMI projector (NexiGo Nova Mini tested)Find
  • Glass vialFind
  • OpenCAL resin (made by Formlabs, sold through MatterHackers)Find
  • 1/8-inch acrylic for the laser-cut partsFind
  • Assorted opticsFind

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Can I build this?

PrintFrame parts, mounts and brackets — exact list in the documentation.
BuyRaspberry Pi 5, Pololu Tic T249 stepper controller, NEMA 17, 8x8 SK6812 RGBW LED array, 20x4 I2C LCD, rotary encoder, Pi Camera Module 3, HDMI projector (NexiGo Nova Mini tested), glass vial, OpenCAL resin (made by Formlabs, sold through MatterHackers), 1/8-inch acrylic for the laser-cut parts, assorted optics, fasteners and electronics — the BOM in the docs totals approximately 1,638 dollars as of June 2026.
ToolsLaser cutter for 1/8-inch acrylic (or an online cutting service such as SendCutSend), a 3D printer that handles PLA, PETG and TPU with at least a 200 by 200 mm bed, soldering iron, Dupont crimping tool, heat gun, metric hex keys, calipers and small hand tools, plus patience for optical alignment.
SkillsIntermediate electronics (wiring a Pi and stepper controller), intermediate mechanical assembly, patience with optical alignment. This is a research instrument, not a consumer kit — expect iteration.
TimeThe documentation states an afternoon once parts are gathered; realistically expect a weekend-plus for the first build, more if optical alignment requires iteration.
Cost$$$. The documented BOM is approximately 1,638 dollars as of June 2026, dominated by the projector, stepper controller, optics and resin.
SafetyThe photopolymer resin requires nitrile gloves and must not be exposed to sunlight during handling. Standard soldering and small electronics care. No mains voltage or lithium concerns beyond the Pi power supply.

Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.

Videos

3D Printing Nerd filmed the machine printing in real time with the OpenCAL team: 'Prints in Seconds - NOW OPEN SOURCE! Computed Axial Lithography!' (youtube.com/watch?v=TWZ4I2GLYgI).

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Gallery

opencal-org.readthedocs.io

Start here

Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.

  1. 1.Read the full documentation (Start with the overview and build guides before ordering parts.)
  2. 2.Review the bill of materials(The BOM totals approximately 1,638 dollars as of June 2026 — verify current prices and availability before committing.)
  3. 3.Download the pre-built Raspberry Pi 5 image(The ready-made image saves configuration time; the control software boots straight into headless mode.)
  4. 4.Prepare to print the frame parts(You will need access to a 3D printer for the structural components.)

Resources

Documentation, files and community threads for this build — we link straight to the original sources and never rehost the creator’s files.

KNOWN ISSUES

  • The licence is non-commercial for end users. If you want to sell prints or machines, you need separate permission from UC Regents — do not assume 'open source' means unrestricted commercial use.
  • The 1,638-dollar figure is the documented BOM total as of June 2026, not a promise of current prices. Verify component costs and availability before ordering.
  • Optical alignment is the single most likely point of failure. The projector-to-vial light path has to be precise or the dose accumulation will be wrong and prints will fail — this is a research instrument, not a consumer kit.
  • The resin is manufactured by Formlabs to the OpenCAL formulation and distributed by MatterHackers, so you are not mixing chemistry yourself, but it still requires nitrile gloves and must never be exposed to sunlight, which cures it in the container.
  • The documentation states assembly takes an afternoon once parts are gathered; realistically expect a weekend-plus for the first build, more if you need to iterate on optical alignment.
  • This is not a drop-in replacement for a layer-based SLA printer. Print files are generated with VAMToolbox (computes the tomographic projections) and prepared with Tomo — the workflow is different.

How fast does it actually print?

The docs say inch-scale parts form in minutes once the projection sequence starts, much faster than layer-based printing. Setup, resin preparation, rinsing and post-cure still take time, so it is not instant end-to-end.

Can I use any resin?

Use the OpenCAL resin. It is a UDMA-based photopolymer that Formlabs manufactures to the OpenCAL formulation and MatterHackers distributes ready to print. Printing depends on the resin's optical properties being right, so other resins will need their own dose tuning.

What projector should I buy?

The build is tested with the NexiGo Nova Mini. Any HDMI projector will work in principle, but the light output and throw distance affect the dose calculation, so stick to the tested model unless you want to recalibrate.

Can I sell prints or machines?

Not under the default licence. The hardware is OCL v1.1 with non-commercial add-ons, and the software is UC Regents non-commercial. If you want to commercialise, contact UC Berkeley.

Community builds

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Discussion1

FROM THE COMPAREE TEAM

The BOM is about 1,638 dollars and the projector-to-vial alignment has to be precise or prints fail, but the whole part cures at once, in minutes, with no supports. Would you build one, or wait for someone to sell a calibrated version?

CompareeTEAM1mo agoedited

Practical notes from our verification: the documentation at opencal-org.readthedocs.io is genuinely complete: CAD, BOM, step-by-step guides and a pre-built Raspberry Pi 5 image. The 1,638 dollar figure is the documented BOM total as of June 2026, not our own costing. The resin is manufactured by Formlabs to the OpenCAL formulation and distributed by MatterHackers, so no chemistry mixing is required. The docs' media page links 3D Printing Nerd's video on the open-source release, along with other coverage. You will also need a laser cutter (or an online cutting service) for the acrylic parts and a 3D printer for the rest. The licence is non-commercial for end users; if you want to sell prints or machines, contact UC Berkeley. The single biggest challenge is optical alignment: this is a research instrument, not a consumer kit, and the projector-to-vial path has to be precise or the dose accumulation will be off. Correction (4 October 2026): we re-checked this page line by line against the project's own repository, documentation and videos, and fixed errors in earlier versions.

Computed Axial Lithography group at UC Berkeley

The project is led by Taylor Waddell with Professor Hayden Taylor at the University of California, Berkeley. The group has flown CAL hardware for in-space manufacturing experiments and is now publishing the complete build so anyone can replicate the technique.

GitHub Web

Star the project on GitHub

DISCLAIMER

  • Comparee is not the author of the projects featured here. All rights to each project belong to its creator — every page links to the original source, and we never host creators’ files.
  • Information is provided without warranty and may become outdated as projects evolve. Prices are indicative bands only — always check the creator’s parts list for current costs.
  • Building and operating any project is at your own responsibility. Protective equipment, safe workshop practice and compliance with local regulations are the builder’s responsibility.
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