A technique that 3D prints an entire object at once, instead of building it up layer by layer, has a heat problem. Researchers at the University of Nottingham, working with the University of California, Berkeley, say they’ve found a fix.
The method in question forms a complete object in seconds by shining patterned light into a spinning container of liquid resin, hardening the whole shape simultaneously rather than tracing it out layer by layer. It’s known in the field as Computed Axial Lithography (CAL), a type of volumetric 3D printing. The chemical reaction that hardens the resin gives off heat as it works, and left unchecked, that heat can warp the finished part, limit how big an object can be printed, and stop the technology from scaling up to larger, more practical uses.
How They Cooled the Reaction Down
To keep the heat in check, the team added a class of chemical additives, known as RAFT agents, to the resin. Rather than cooling the print from the outside, these additives work inside the chemical reaction itself, slowing it down and keeping it from speeding out of control.
“It acts like a built-in ‘regulator’ for the reaction, both slowing and regulating how the material is formed. This prevents sudden heat spikes and keeps the printing process stable and predictable,” said Eduards Krumins, a Research Fellow in the Additive Manufacturing Research Group at Nottingham’s Faculty of Engineering.
After testing five versions of these additives, the team found one that worked best. Adding a small amount to a commonly used 3D printing resin cut the temperature rise during printing from 59°C down to 27°C, and a slightly larger amount brought it down to just 3.5°C. The fix worked across resins with very different thicknesses, including a water-based gel material used for medical 3D printing.
Printing Multiple Parts at Once, Without Them Fusing Together
With the heat under control, the researchers were able to print several separate objects in the same container at the same time, spaced as little as 150 micrometers apart, without them melting into one another the way they did before. The same approach also made it possible to print interlocking parts, like a hinge that could freely rotate right out of the 3D printer, and objects nested inside other objects in a single print.
The added chemicals also leave the 3D printed material open to further treatment after printing is done. The team used this to coat printed surfaces with materials that resist bacterial buildup, a step toward printing objects with more than one function built in.
A Chemistry Fix for a Persistent Limit
Nottingham and Berkeley’s approach targets a specific bottleneck holding back this printing method’s ability to scale up: heat management, addressed at the resin chemistry level rather than through external hardware.
Heat has been a recurring obstacle in resin-based 3D printing generally. Northwestern University researchers hit the same wall building HARP, a high-speed resin printer, and found that heat generated during fast printing caused parts to crack and deform, worsening as the printer scaled up in size. They fixed this mechanically by using a nonstick fluorinated oil that flows across the printing window to carry heat away and keep temperatures steady during printing.
Seen alongside that earlier approach, the Nottingham and Berkeley method suggests there’s more than one way to solve 3D printing’s heat problem, whether by removing it from the outside or, as in this case, controlling it from within the resin itself.
Titled “Enhanced volumetric additive manufacturing via Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization,” the study was conducted by Eduards Krumins, Yaxuan Sun, Long Jiang, Vincenzo Taresco, Daniel J. Keddie, Ricky D. Wildman, Hayden Taylor, and Derek J. Irvine.
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