University of Colorado Boulder unveils OpenVCAD for multi-material 3D printing

The hardest part of multi-material 3D printing has often been the design file, not the machine. University of Colorado Boulder researchers have unveiled OpenVCAD, an open-source tool built to let engineers describe where materials should change inside a part, then compile that intent into output printers can use.

At the Matter Assembly Computation Lab, led by assistant professor Robert MacCurdy in the Paul M. Rady Department of Mechanical Engineering, the project is aimed squarely at a bottleneck the community knows well. Standard CAD and slicer-based color or material workflows are still awkward when a part needs more than a clean swap from one material to another. OpenVCAD is meant to handle the jobs those tools still treat badly, including gradients, spatially varying material zones, and transitions that need to shift from rigid to flexible or from structural to compliant inside the same print.

The lab describes OpenVCAD as a unified framework for volumetric, multi-material, programmable design and AM-ready compilation. It couples an implicit modeling core with a compiler that emits printer- and simulation-ready outputs, which matters because the point is not just to draw a shape but to turn material intent into something a machine can actually build. The public GitHub repository presents it as an open-source volumetric geometry compiler for functionally graded, multi-material objects, and the project is documented as active software.

CU Boulder said Charles Wade, a fourth-year PhD student in computer science, developed the system, and the team tested it across multiple printers, including one in MacCurdy’s lab capable of printing with up to five materials at once. That hardware backdrop reinforces the software’s purpose: not novelty demos, but real parts such as gradient shoe soles and surgical practice models where different sections need different behavior. The lab’s publications page lists the original paper, OpenVCAD: An open-source volumetric multi-material geometry compiler, in Additive Manufacturing, volume 79, published in 2024, and the lab says the framework has since expanded into later work on gradient-aware slicing and a Python-first API extension.

For advanced makers, that shift is the story. OpenVCAD moves multi-material printing upstream, away from the frustrating last mile of slicing tricks and manual workarounds, and toward a more programmable design process that can match the capabilities of increasingly sophisticated printers.