OpenCAL: Build an Open-Source Volumetric 3D Printer That Prints in Seconds

How OpenCAL works

Standard desktop 3D printers build objects layer by layer. That approach gives you visible layer lines and long print times. OpenCAL skips all of that.

The system rotates a glass cylinder filled with viscous photopolymer resin while a compact projector shines 450-nanometer blue light through it from multiple angles. Light energy accumulates at specific coordinates inside the resin, hardening the entire geometry in a single pass. No Z-axis movement. No slicing. No layer lines.

In a demonstration by UC Berkeley researcher Taylor Waddell, a fully formed miniature space shuttle emerged from the resin in about 20 seconds. Because the part cures all at once, there are no weak interfaces between layers.

What you need to build one

OpenCAL is designed around accessible hardware. A Raspberry Pi manages the system and streams continuous MP4 video directly to the blue laser projector. The printer locks alignment with a custom three-axis screw-adjustment mount that positions the light precisely at the cylinder's center point.

Most structural parts can be 3D printed on an existing machine. The estimated materials cost is around 1,400 dollars, with the laser projector accounting for most of that expense. Full firmware is available on the OpenCAL GitHub repository, and step-by-step build documentation walks through assembly.

Resin and safety

The project partnered with Formlabs and MatterHackers to supply pre-mixed photopolymer resin at cost, so builders do not need to mix volatile chemicals. Normal print cycles generate moderate heat from the exothermic curing reaction.

One real warning from the research team: bulk resin vials left in direct sunlight can trigger runaway reactions reaching 230 degrees Fahrenheit. Store resin away from direct light.

Post-processing

After exposure, operators rinse away uncured resin with isopropyl alcohol, then place the part in water for a final ultraviolet cure under sunlight or a UV station. That workflow will feel familiar to anyone who already owns a resin printer.

Why this matters

Consumer 3D printing has been stuck in the layer-by-layer paradigm for years. OpenCAL does not replace FDM or standard resin printing for every use case, but it opens a genuinely different path. A fully open-source build that fits in checked luggage, costs under 2,000 dollars, and produces isotropic parts in seconds is a meaningful shift.

The GitHub repository and documentation are publicly available now.