San Diego County has sued Polymaker, a maker of 3D printer filament, alleging the firm sells that material to California customers in ways that let people print firearms at home.

County officials say Polymaker goes beyond supplying raw material by marketing it to gun printers through influencers and by offering technical help, even though such printing can violate state law. They cite the company’s ties to Sean Aranda, whose YouTube channel 3D Print General covered practical 3D firearm printing, plus a related book and podcast, until YouTube deleted it in 2023 for firearms-content violations when it had 123,000 subscribers.

After the channel was removed, Polymaker sold a khaki filament spool in a partnership with Aranda, later hired him as head of customer experience, and now employs him as senior technical account manager.