OpenCAL Is an Open-Source Volumetric 3D Printer That Works in Seconds

What is Computed Axial Lithography?

Standard 3D printers build objects layer by layer, whether they extrude plastic or cure resin one slice at a time. Computed Axial Lithography, or CAL, takes a fundamentally different approach. Instead of stacking layers, it rotates a glass cylinder filled with viscous resin while projecting light through it from multiple angles. The intersecting light patterns harden the liquid into a solid part all at once.

The result is a printing speed that looks like magic. In demonstrations, researchers have produced miniature objects in under 20 seconds. There are no layer lines, no Z-axis movement, and no long waits for the build plate to rise.

OpenCAL Brings the Technology Down to Earth

Until recently, CAL systems required custom lab-built optics and university-level budgets. OpenCAL changes that equation. The project, led by researcher Taylor Waddell, releases all firmware, design files, and build instructions under an open-source license. The hardware relies on a Raspberry Pi, a standard blue-light projector, and a 3D-printed frame. The total material cost runs around $1,400, with the projector making up most of that expense.

The build process is straightforward. The printer spins a resin-filled cylinder while a projector delivers calibrated light patterns. A three-axis screw mount handles alignment, which is critical because the light has to pass through the center of the cylinder with millimeter precision. Once the exposure finishes, the part gets a quick spin cycle or isopropyl bath to remove uncured resin, then a final UV cure in sunlight or a wash station.

The open-source release includes step-by-step documentation and pre-configured software that streams MP4 light patterns directly to the projector without requiring custom slicers or G-code translation.

Why It Matters for Makers

Speed is the obvious appeal, but there are other advantages. Because the entire object forms at once, there are no weak interlayer bonds. Surface finish comes out smooth without extensive post-processing. The contained vat also limits resin exposure to the air, which could reduce the vapor and odor problems that plague traditional resin printers.

The current limitations are real. The resin library is smaller than what SLA and DLP users enjoy, and large prints still stress the system. The photopolymer reacts exothermically during curing, generating heat, and bulk resin left in direct sunlight can run away to dangerous temperatures. But for small functional parts, prototypes, and miniatures, OpenCAL offers a compelling alternative.

A New Path for Desktop Manufacturing

OpenCAL does not replace filament printers or standard resin systems overnight. What it does is prove that volumetric printing can escape the research lab. With community documentation, affordable parts, and a working reference design, the platform gives makers a genuine chance to experiment with layerless manufacturing.

Anyone can download the firmware and build guides today. The team partnered with Formlabs and MatterHackers to supply tested resin at cost, lowering the barrier for first builds. If the project gathers momentum, the same open-source model that accelerated FDM and standard resin printing could push CAL into the mainstream.