OpenCAL publishes a 1,400 dollar open-source build of a volumetric resin printer

A UC Berkeley team has released OpenCAL, an open-source design for building a computed axial lithography printer, which forms a whole part in a rotating resin vial within minutes. The kit costs about 1,400 dollars and can be assembled in an afternoon. It moves a process that has mostly stayed in academic labs into makerspaces and small workshops.

Context Computed axial lithography is a volumetric process: instead of curing resin layer by layer, projected light patterns from many angles cure the whole part at once inside a rotating vial.

How does computed axial lithography work?

A vial of photoresin rotates while a computed series of images is projected through it. Where enough light accumulates, the resin solidifies, and the rest stays liquid. The principle is tomographic reconstruction, comparable to a CT scan run in reverse. The open-source VAMToolbox calculates the light dose from a 3D model. According to the team, inch-scale objects form in minutes, with no layers and no support structures.

What does the OpenCAL build consist of?

The frame uses pre-cut 2020 aluminium extrusion. The optics rely on an off-the-shelf 1080p DLP laser projector and a Fresnel lens, and a Raspberry Pi 5 with a Pi Cam handles control and monitoring. A 3D printed rotary stage, a stepper motor, a 20x4 LCD and a linear X-Z stage for the projector complete the machine. Tools needed are an ordinary FFF printer, hand tools, soldering equipment and optionally a laser cutter. The design is split into frame, optics and electronics subsystems, and many parts can be replaced with items from a well-equipped shop.

How are parts printed, washed and cured?

Instead of G-code, the machine plays MP4 video files uploaded to the Raspberry Pi. VAMToolbox is being condensed into a GUI workflow: import an STL, voxelize it, then optimize the image sequence. Washing is either an IPA bath of about 40 minutes or a centrifugal spinner built by the team. Parts come out more undercured than in SLA or DLP, so they need careful handling, and final curing takes place in a water bath to avoid a sticky surface. Unused resin can be reused.

What is over-printing, and what about resin supply?

Because the part is not built in layers, an existing object can sit in the vial and the projections can add material around it, for example a handle around a screwdriver bit. The team compares this to low-volume injection moulding and has added an encoder and imaging system that may later detect inserted objects automatically. Through partnerships with Formlabs, the team expects one-litre resin quantities for around 100 dollars. The authors warn that early builders should expect many failed prints.

What it means

OpenCAL is a learning and research platform, not a production tool. For small and mid sized manufacturers it is a low-cost way to build in-house understanding of volumetric printing, including the unusual post-processing and the over-printing idea, before any commercial systems exist. Part quality, material range, qualification and repeatability are not addressed, and the authors expect failed prints. Realistic business cases are some way off, and resin availability through Formlabs is still an expectation, not a product.

Frequently asked questions

What is OpenCAL?

OpenCAL is an open-source platform from a UC Berkeley team for building a computed axial lithography printer, covering the machine, the software and resin sourcing.

How much does it cost and what is needed to build it?

The project lists a price of 1,400 dollars. Builders need an FFF printer, hand tools, soldering equipment and optionally a laser cutter.

Can it print production parts today?

The authors describe it as an experimental machine in the spirit of early desktop 3D printing, with failed prints to be expected.

This summary was written with the help of AI from the linked reports, under the editorial responsibility of Svetozar Kolesar.