A European Patent Office Board of Appeal has kept Carbon's foundational dual-cure patent alive. In a release dated September 28, 2026, the resin-printing company said the Board rejected a competitor's challenge to European Patent 3158400, upholding its broadest claim and restoring dependent claims that had been removed during the opposition stage. The Board heard the case on September 24. The official outcome, as reported by 3D Printing Industry, is "maintenance in amended form."
That phrase matters, and it is easy to skim past. The patent was not revoked, which is the outcome an opponent wants. It also did not emerge untouched. This piece sets out what the record shows, what it does not show, and what a maker should and should not read into it.
The timeline
According to 3D Printing Industry's report of September 30, the patent is titled "Methods of Producing Three-Dimensional Objects from Materials Having Multiple Mechanisms of Hardening." It was filed on June 22, 2015, and granted on June 1, 2022. The sequence after grant was short and then very long:
- February 27, 2023: Oxon IP B.V. filed an opposition.
- November 21, 2024: The Opposition Division held its hearing.
- January 3, 2025: The Opposition Division's decision was dispatched.
- Appeal case T0373/25: The matter went to the Board of Appeal.
- September 24, 2026: The Board held oral proceedings, issued its result the same day, and the patent was maintained in amended form.
Counted from the opposition filing to the Board's hearing, that is about three and a half years. Counted from grant, the patent was under challenge for most of its life so far. Opposition at the EPO is a post-grant mechanism that lets a third party ask the office to revoke or narrow a patent shortly after it issues. The first-instance decision can then be appealed, which is what happened here.
What was actually decided
The description of the Board's effect on specific claims originates with Carbon, which is a company statement, and the trade report attributes it to the company ("Carbon states"). The company says the Board upheld the broadest claim of EP 3158400 and restored dependent claims that were removed in the opposition. In patent practice, the independent claim sets the outer boundary of protection, and dependent claims layer narrower, more specific positions beneath it. Losing dependent claims leaves fewer fallback positions if the broad claim is later attacked elsewhere. Getting them back gives the patent more depth.
The "amended form" outcome means the text that survives is not identical to what was granted in 2022. Neither of our sources reproduces the amended claim language, and we have not seen it. We therefore cannot say precisely how the surviving scope differs from the granted version, and we are not going to guess. Anyone who needs to know exactly what is covered would need to read the maintained claims in the patent record or ask counsel.
Likewise, the opponent is named in the trade report as Oxon IP B.V., which that report describes as a patent law firm in Schiphol, the Netherlands. Carbon's release describes the challenger only as a competitor and does not name it. Our sources do not establish who, if anyone, stood behind the opposition, and we do not draw a conclusion about it.
What dual cure is
Carbon's release describes dual-cure as combining light-based printing with a secondary thermal cure. The patent title, with its reference to "multiple mechanisms of hardening," points in the same direction. The release frames this as foundational to Carbon's approach to producing parts. We are relying on the company's own characterization here, and neither source provides independent technical analysis of how narrowly or broadly the surviving claims capture the process.
For readers who work with photopolymer resins, the practical point is that post-print thermal treatment is a familiar step in many workflows. Whether any given resin, printer or workflow falls inside the maintained claims is a legal question that turns on claim language, and this article cannot answer it. A patent covering a specific method of producing objects from materials with multiple hardening mechanisms is not the same thing as a patent on baking a print.
The people involved
Carbon's release quotes CEO Philip DeSimone and lists the outside counsel on the matter: Marks & Clerk, Myers Bigel and Winston Taylor. The roster says nothing about the merits.
The wider patent climate
3D Printing Industry places the decision against a busy backdrop of intellectual property disputes in additive manufacturing. It points to Continuous Composites v. Markforged, which produced a $17.34 million verdict and a $25 million settlement, and to a new suit against FibreSeek and Anisoprint. Those cases involve a different company and different technology, composite fiber placement rather than resin curing, and they are not connected to Carbon's patent. They are useful as a reminder that patent enforcement in this industry is active and can be expensive for the defendant.
The contrast is also instructive. A verdict and a settlement describe what happens after a patent is asserted in court. An EPO opposition describes what happens when someone tries to remove the patent before it is ever asserted. Carbon's win is of the second kind. It strengthens the patent's standing in the European system, and nothing in our sources says Carbon has sued anyone over EP 3158400.
What It Means for Makers
For most hobbyists, very little changes tomorrow. Nothing in the sources indicates Carbon is targeting individuals or small shops, and nothing indicates any product has been withdrawn. The practical effects fall on companies that build or sell resin systems with multi-stage hardening chemistry, especially those operating in Europe, because a challenged patent has now survived the main route for removing it.
Still, three points are worth keeping in mind.
- Survival is not the same as breadth. The patent was maintained in amended form. Until someone reads the surviving claims against a specific process, "upheld" is a headline rather than a scope analysis.
- The result is regional. This is a European patent decision. We have no information in our sources about how related patents fare in other jurisdictions, and one jurisdiction's outcome does not bind another.
- Vendor statements deserve care. The detailed description of the Board's treatment of the claims comes from Carbon's own release. The trade report confirms the outcome label and the procedural timeline, but we have not independently verified the claim-by-claim details.
If you sell parts made on a resin platform with a secondary thermal step, or you are building one, the sensible reaction is attention, not alarm. Ask your supplier or counsel whether the maintained claims touch your process. If you simply print and bake your own parts, nothing in this decision tells you to stop.
Bottom line
After more than three years of procedure, spanning an opposition, a first-instance hearing, an appeal and a September oral hearing, Carbon's EP 3158400 stands, in amended form, with its broadest claim intact. It is a meaningful procedural victory for the company and a reminder that post-grant fights over patents can take longer than many product cycles. The next thing to watch is the published text of the amended claims, because that, and not the press release, will define what the win actually protects.
