Goodbye stereolithography An STL-free strategy redefines metal 3D printing

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What if metal 3D printing no longer needed STL files? Researchers have demonstrated an STL-free approach to laser powder bed fusion that delivers microscale lattice structures with dramatically improved strength, surface quality and computational efficiency.

For decades, stereolithography (STL) files have been the quiet workhorses of 3D printing, converting digital designs into printable layers. But they also come with baggage: clunky file sizes, geometric approximations, and limits on how fine a structure can be built. Now, an international team of researchers has found a way around these constraints.

In the International Journal of Extreme Manufacturing, the team proposed an “STL-free hybrid toolpath strategy” for laser-based powder bed fusion (PBF-LB). Instead of relying on mesh-based STL conversions, the method feeds the printer a direct mathematical description of geometry — essentially cutting out the middleman. Their result is unprecedented, with lattice walls just 65 microns thick (about the width of a human hair) and surfaces as smooth as 3.2 microns, all achieved with 90 percent less memory demand.

“By bypassing STL conversion and operating directly on implicit functions, we reduce memory usage and also unlock far better mechanical and surface properties,” explained Prof. Xu Song of The Chinese University of Hong Kong, the paper's corresponding author.

The method’s key lies in its hybrid strategy: contour scanning for delicate thin walls, paired with rotational scanning at lattice joints. This dual approach stabilizes heat input, minimizes structural defects, and promotes uniformity in crystal, which is crucial for strength and toughness at the microscale.

Beyond a 90 percent reduction in memory use and processing time, their new strategy also enables the high-fidelity fabrication of microscale shell lattices with a 66 percent increase in yield strength and 257 percent improvement in elongation. Tests under cyclic loading and fracture studies further confirmed the parts' durability.

As a result, their potential impact could be wide-ranging. A lightweight aerospace bracket printed with this strategy delivered 52 percent higher tensile strength and absorbed five times more energy before failure compared with parts made conventionally, and copper cold plates built with the method boosted cooling efficiency by 60 percent.

“Our method bridges computational design and physical fabrication in a seamless way,” said co-author Prof. Wen Chen from the University of Southern California. “It opens up new possibilities for high-performance microscale structures in fields like aerospace, biomedicine, and electronics.”

The researchers see this as just the beginning. Their next steps are to expand this strategy to new materials and integrate microstructure-aware path planning to further tailor mechanical performance. That could lead to architected metamaterials that combine strength, ductility, and long-term durability in most efficient ways that no current 3D printing method can achieve.

By rethinking the very link between digital design and physical build, this STL-free strategy also reframes what is possible in advanced manufacturing — where lighter, stronger, and smarter parts are not just desired, but required.

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