Bambu Lab Patent Verdict Puts Purge Towers on Trial

A Bambu Lab patent fight just left the forums. On September 18, 2026, TCT reported a Marshall jury awarded Stratasys about $27.6 million in past damages on four U.S. patents, including the purge-tower method behind the plastic brick next to a color print. If you keep a desktop machine, this is about how shared-nozzle color changes work — not a ban on owning a printer, and not a last word while Bambu says it will appeal.

What's Happening

TCT’s September 18 report is the source for the verdict and the statements that follow. After a week-long trial, a Marshall, Texas jury found four patents valid and infringed: United States Patent Nos. 9,421,713, 7,555,357, 9,168,698, and 10,556,381. TCT names the defendants as Bambu Lab and affiliates Shanghai Lunkuo Technology, Tuozhu Technology Limited, and Shenzhen Tuozhu Technology. The award TCT cites is about $27.6 million in past damages — the jury’s number in this first case, not a global fine already collected.

TCT identifies 9,421,713 as the core purge-tower patent. Google Patents lists that 2016 Stratasys grant as “Additive manufacturing method for printing three-dimensional parts with purge towers.” Published claims cover switching print heads between standby and operating modes and purging by printing tower layers. TCT does not chart the other three patents, so this article does not invent those claims. A fifth asserted patent, 9,592,660, was held invalid at PTAB; TCT says Stratasys did not appeal.

Bambu Lab’s statement, as TCT quotes it, disagrees with the verdict and says the company will seek post-trial review and appeal. Bambu also told TCT that PTAB found 8,562,324 invalid, that PTAB previously upheld 9,421,713 and Bambu has appealed that patent to the Federal Circuit, and that the Unified Patent Court in The Hague dismissed a Stratasys preliminary injunction on April 24, 2026, for EP2964450 — which Bambu calls the European counterpart of U.S. 9,421,713. Stratasys, per TCT, thanked the jury and noted that a second U.S. patent case is not yet set for trial.

Why This Bambu Lab Patent Fight Matters for Makers

Most hobby color prints on a single-nozzle or shared-melt path spend real filament on a wipe tower. That brick is not a slicer flourish. It is the physical record of a material swap: old melt out, new melt in, so the next perimeter is not streaked. When a jury in Texas treats that workflow as patented, the argument leaves Reddit and lands in the same category as firmware locks and filament DRM — things that change how cheap a multi-color job feels, even if your machine still sits on the bench tomorrow morning.

The practical split on a garage desk is architecture, not brand loyalty. A tool-changer parks several hot ends and picks one, so it often skips a shared-nozzle purge. A single-nozzle multi-material unit has to empty the melt zone somehow. Petsiuk and colleagues measured how expensive that second path can be when slicers change color on every layer: wipe towers that outweigh the object, plus extra time and energy (Petsiuk et al., 2024). A verdict does not rewrite those physics. It does put a dollar figure on who claims the tower method in U.S. court.

How Bambu Lab Patent Claims Map to a Desktop Job

• Shared-nozzle color change. One melt path, several filaments. The printer parks leftover plastic in a purge tower (or into infill, or into a “purge object”) so the next color is clean. This is the workflow U.S. 9,421,713 describes in published claims.
• Tool-changing head. Separate nozzles, one active at a time. Prime towers can still appear, but the classic “flush the old color through one nozzle” problem is smaller. Prusa’s INDX-class machines sit in this bucket; TCT’s verdict story does not name them.
• Independent dual extrusion. Two nozzles that can print at once or take turns. Purge still happens, but it is a different mechanical story than a single AMS-fed hot end.
• Continuous-fiber co-extrusion. A thermoplastic path plus a continuous tow path. That is for stiffness, not for swapping PLA colors. It is not the dispute TCT reported.
• What the jury did not do. TCT does not list accused Bambu SKUs. The second U.S. case is unscheduled. Europe already went the other way on a preliminary injunction, according to Bambu via TCT. Petsiuk’s clustering work is one published way to cut tool changes without new hardware (Petsiuk et al., 2024).

What the Research Says

Petsiuk, Bloch, Vogt, Debora, and Pearce started from a fact every multi-color owner already knows: slicers that swap material on every layer often grow a wipe tower heavier than the model. They implemented interlayer tool clustering in a PrusaSlicer fork so same-color regions stack across several layers before a swap, without requiring a new printer. On their test objects the method cut material use about 1.7 times on average, cut print time and energy about 1.4 times, and cut material transitions about 2.4 times. Those numbers are their experimental averages, not a measurement of any Bambu or Stratasys machine named in TCT (Petsiuk et al., 2024). The paper is about g-code order. It is the research reason a purge tower is a process choice, not a law of nature.

Beltrán, Arrieta, and colleagues took the waste stream those towers feed. They washed PLA 3D-printing scrap, extruded it, and compression-molded films, comparing a homogeneous reference grade with a mixed-waste blend. Mechanical recycling raised crystallinity and dropped intrinsic viscosity, worse in the mixed lot. Films still composted in under a month, and a bit faster than the starting filament because the chains were shorter. Solid-state polymerization at 110–130 °C helped restore viscosity for the known grade and did little for the mixed wastes. Their conclusion is operational: distributed recycling works when you keep grades separate, not when you melt every purge brick into one mystery pellet (Beltrán et al., 2021). That is the shop-floor sequel to a patent fight about towers. Someone still has to do something with the plastic.

Frequently Asked Questions

What is a Bambu Lab patent verdict in the Stratasys case?

TCT reported a Marshall, Texas jury awarded Stratasys about $27.6 million in past damages after finding four U.S. patents valid and infringed. Bambu Lab says it disagrees and will seek post-trial review and appeal. A fifth patent was held invalid at the PTAB. A second U.S. case is not yet scheduled.

How does purge tower 3D printing work on a desktop machine?

When one nozzle must switch filaments, leftover melt is purged into a sacrificial tower so the next color is clean. Stratasys’s U.S. Patent 9,421,713 covers printing that tower layer by layer as heads switch between standby and operating modes. Tool-changing printers can avoid a shared-nozzle purge.

Does the Bambu Lab patent case affect continuous-fiber printers?

TCT’s report is about Stratasys and Bambu Lab affiliates in Texas, not about continuous-fiber co-extrusion. A desktop continuous-fiber printer lays thermoplastic plus carbon or glass tow for stiff parts. That is a different extrusion job than parking a color change in a purge tower.

Fibricate's Place in This Story

A jury verdict about shared-nozzle purge methods does not tell a shop how to print a stiff bracket. Companies like Fibricate, whose FibreSeeker 3 continuous carbon fiber 3D printer co-extrudes thermoplastic with tow from feedstock such as the continuous carbon fiber spool, sit on that other bench: functional parts, not AMS color swaps. Keep the lanes separate. Watch the Texas docket if you buy or sell shared-nozzle color machines. Use continuous fiber when the job is stiffness, and do not pretend a purge-tower patent chart is a materials spec.

What to Watch Next

Watch post-trial motions and the Federal Circuit appeal Bambu says it will file. Watch whether the unscheduled second U.S. case gets a date, and whether any injunction language — TCT did not report one in this piece — appears later. Watch the European invalidation Bambu says it started on EP2964450; a Hague PI denial is not the same as a patent dying. For makers, the 12–24 month signal is simpler. Multi-color desktop printing will keep splitting into tool-changers, shared-nozzle systems, and people who print one color and walk away. Know which line your machine is on before the next verdict, not after a firmware surprise.

References & Further Reading

1. Petsiuk, A., Bloch, B., Vogt, D. K., Debora, M., & Pearce, J. M. (2024). Tool change reduction for multicolor fused filament fabrication through interlayer tool clustering implemented in PrusaSlicer. Rapid Prototyping Journal.
2. Beltrán, F. R., Arrieta, M. P., Moreno, E., Gaspar, G., Martínez Muneta, M. L., Carrasco-Gallego, R., Yáñez, S., Hidalgo-Carvajal, D., de la Orden, M. U., & Martínez Urreaga, J. (2021). Evaluation of the Technical Viability of Distributed Mechanical Recycling of PLA 3D Printing Wastes. Polymers.
3. Stratasys awarded $27.6m in damages in first of two patent infringement cases against Bambu Lab. TCT Magazine. Retrieved September 18, 2026.