A Board of Appeal at the European Patent Office (EPO) has maintained Carbon’s European Patent No. 3158400 in amended form, closing a proceeding that ran through two levels of EPO review over roughly three and a half years.
Titled “Methods of Producing Three-Dimensional Objects from Materials Having Multiple Mechanisms of Hardening,” the patent covers a process that pairs light-based 3D printing with a secondary thermal curing step. Carbon states the technology is used in automotive, dental, medical, and consumer product manufacturing. The patent was filed on June 22, 2015, and granted on June 1, 2022.
“This decision confirms the strength and breadth of the innovation that is foundational to Carbon’s platform. Dual-cure chemistry enables the production of high-performance end-use products that previously were difficult or impractical to produce with other 3D printing technologies. We will continue to invest in and protect our innovations as we advance digital manufacturing,” said Philip DeSimone, CEO of Carbon.
Carbon’s Patent Faces EPO Opposition
According to the European Patent Register, the opposition was filed on February 27, 2023, by Oxon IP B.V., a patent law firm based in Schiphol, the Netherlands. Carbon’s press release refers only to “a competitor’s challenge” and does not name the opposing party.
This discrepancy is common in European patent disputes, where companies utilize European patent firms to file “straw man” oppositions. This legal mechanism allows an anonymous commercial competitor to fund and direct the challenge without being named in the public record.
Carbon filed its reply in July 2023. The EPO’s Opposition Division, the first-instance body that hears patent challenges, held oral proceedings on November 21, 2024. The written decision was dispatched on January 3, 2025. Carbon states that decision maintained the patent’s broadest claim, known as claim 1, but removed several narrower dependent claims.
Two appeals were then filed against the Opposition Division’s decision, one in late February and another in early March 2025, both assigned case number T0373/25. The Board of Appeal, which serves as the EPO’s final review body, held oral proceedings on September 24, 2026, and issued its result the same day.
The formal outcome recorded in the register is “maintenance in amended form,” meaning the patent survived but differs from how it was originally granted. Carbon states the Board of Appeal upheld claim 1 and restored the dependent claims the Opposition Division had removed.
Carbon is represented in the EPO proceedings by Marks & Clerk LLP, London. The company’s press release also names Myers Bigel as its global patent prosecution counsel, and Kathi Vidal and Dustin Edwards of Winston Taylor as patent litigation counsel.
Patent Survival Opens Enforcement Options
The outcome follows a broader pattern of patent enforcement in production-grade 3D printing. In April 2024, a jury in the United States found that Markforged had infringed a patent held by Continuous Composites covering continuous fiber 3D printing processes, awarding $17.34 million in damages. The two companies subsequently settled the case for $25 million total, including cross-licenses and mutual releases.
Last month, Continuous Composites filed a new patent infringement suit, this time against FibreSeek and two Anisoprint entities, asserting ten patents from the same family in the US District Court for the District of Delaware. The company had attempted to negotiate a license with FibreSeek since 2023 without reaching an agreement.
A process patent that survives a challenge confirms that the patent has withstood the relevant validity challenge, but any subsequent licensing or litigation against other companies would depend on the specific patents, claims, activities, and jurisdictions involved. Carbon’s patent has now cleared two levels of EPO review. Whether that leads to similar enforcement actions in Europe remains to be seen.
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Featured image shows Carbon DLS system printing lattice saddle. Photo via Carbon.
