Instant Prints! OpenCAL Layerless 3D Printing - Make:

Instant Prints! OpenCAL Layerless 3D Printing - Make:

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Instant Prints! OpenCAL Layerless 3D Printing

Now you can build OpenCAL, the world’s first layerless, all-at-once 3D printer

Time Required: An afternoon<br>Difficulty: Moderate<br>Price: $1,400

Print this Project

This article appeared in Make: Vol. 97. Subscribe to Make: for the latest articles.

Computed axial lithography , or CAL, looks different from other forms of 3D printing. A vial of resin rotates while a sequence of carefully computed images are projected through the volume. Where enough light accumulates, a part forms — all at once, in just minutes. There are no layers and no support structures. Introduced by our team at UC Berkeley in 2019, the CAL process was covered by Make: in Volume 88, but now we have a new development: a DIY version you can make at home.

The CAL team have condensed much of our lab setup into a new, accessible open-source platform. OpenCAL is a project designed to let the public build, test, and contribute to the volumetric additive manufacturing (VAM) community.

The project covers machine construction, the software needed to fabricate parts, and resources for obtaining the resin. Once you’ve gathered the components and 3D printed the parts, the machine can be assembled in an afternoon.

How CAL Printing Works

Illustration by Rob Nance

The core idea behind OpenCAL remains the same — tomographic reconstruction . It’s like a CT scan in reverse. In a CT scan, X-rays are used to measure a person’s internal structure and then computers reconstruct it volumetrically. In CAL, the process starts with a 3D model. From that model, the software computes the projected images needed to reconstruct the part in resin. The open-source software that drives this is called VAMToolbox . It calculates light dosage so that only the regions meant to form the part receive enough light to solidify, while the rest remains liquid.

As the light passes through the spinning vial, it is effectively delivering a dose of photons to the whole part at once. Because of that, machines like OpenCAL can print much faster than traditional methods, with inch-scale objects forming in mere minutes.

Building Your OpenCAL Printer

OpenCAL was designed to require as little specialized equipment as possible. The build calls for a basic set of hand tools, a 3D printer, and optionally a laser cutter. The frame is made from pre-cut 2020 aluminum extrusion and brackets, the optical system uses a compact DLP laser projector and a Fresnel lens, and the electronics are powered by a Raspberry Pi 5 with a Pi Cam. We designed the project so that the parts can be ordered from common suppliers and delivered quickly, but we also left room for substitutions: many of the components can be swapped for parts already found in a well-equipped shop or makerspace.

Stepper motor

3D-printed rotary stage

Skateboard bearings

Glass vial with photoresin

RGB LED grid provides illumination

Pi Camera watches prints for completion

Raspberry Pi inside! USB access on top

Fresnel lens in 3D-printed shroud

Display interface, 20×4 LCD with selector knob

1080p mini DLP laser projector, off the shelf

Linear X-Z stage adjusts projector position

Standard aluminum extrusion, 20mm×20mm

24V DC power supply and buck converters

The build itself follows a familiar pattern from other open-source machines. Instead of one complicated assembly, the system is broken into smaller subsystems. Makers work through the frame, optics, and electronics separately, then bring everything together at the end. The design was also intended to introduce users to the core ideas behind the technology and to show which subsystems matter most. In some cases, that means design decisions that may not be obvious at first, such as making the main rotational holder one solid piece to preserve accuracy.

Even so, this will likely feel more like the early days of desktop 3D printing, when the machines were still a hobby and not yet routine tools. Builders will be working with something new, and good results will depend on a range of factors, including precise rotation, optical alignment, and properly generated projections. Early users should probably expect as many failed prints as successful ones. But we believe the maker community will be essential in turning this from an experimental machine into a more common fabrication tool.

Printing and Post Processing

Instead of G-code, the machine uses simple MP4 video files uploaded to the Raspberry Pi. A basic GUI allows users to select print files, adjust speeds, and control other aspects of the hardware. The core software used to generate those projections, VAMToolbox, is also being...