Files containing mechanical drawings, case measurements and recommended materials have been released by Nokia.
According to the BBC, those using the files will be able to create a custom-designed case for the flagship Lumia 820 handset.
The project has made Nokia one of the first big electronics firms to seriously back 3D printing.
In a blogpost, John Kneeland, one of Nokias community managers, revealed the Finnish phone makers decision to release the 3D drawings.
According to the report, printing in 3D involves sending a design file to a printer that then forms a solid version of that object by slowly building it up in layers of plastic.
Early 3D printers could only work in one colour, but the latest versions can produce intricate, multi-coloured objects.
Kneeland said Nokia was releasing what he called a 3D printing development kit to help people produce the cases.
He said that 3D printing was another way that the firm wanted to build links to that vast community of software and hardware engineers. To get the files, users must have registered with Nokia.
In the future, he said, 3D printing was likely to bring about phones that were wildly more modular and customisable, the report added.