Key takeaways
- RepRap (since 2004) and Voron Design (since 2015) publish drawings under the GPL — anyone may modify, reprint and resell, including assembled printers. Neither sells assembled machines itself; builders buy parts from the BOM.
- Voron Design publishes three main lines: Voron 0 (120×120×120 mm), Voron 2.4 and Voron Trident (both with 250, 300 and 350 mm options) — one set of drawings, with the builder choosing a size when buying parts.
- Prusa published OpenSCAD files for the i3 line through the MK3 under the GPL. CORE One (launched late 2024) was its first printer without full hardware files at launch.
- In December 2025, Prusa republished CORE One's CAD files under its own Open Community License (OCL): you may modify, print spare parts and use it in your own workshop, but not sell assembled printers or derivative products without a separate agreement with Prusa.
- Open source doesn't mean easy. There's no manufacturer warranty for the whole machine, no support hotline, and most of the early time goes into assembly and tuning rather than printing.
"Open source" is often used like a marketing sticker, when it's really a question about the licence: what you may copy, what you may modify, and what you may resell. The three examples below — RepRap, Voron Design and Prusa Research — answer that question three different ways, and the difference between them is far bigger than the difference between two printers in different-coloured shells.
RepRap: where the movement began
RepRap was introduced online by Adrian Bowyer in February 2004, with a clear goal from the start: a printer that could print some of its own parts. The project described itself as a "self-replicating rapid prototyper", and every drawing was released under the GNU GPL — anyone may copy, modify and redistribute, free of charge.
Voron Design: sells drawings, not printers
Voron Design is a non-profit organisation founded in 2015 that publishes specifications for high-performance 3D printers and doesn't sell assembled machines. Voron's whole value lies in its drawings, bill of materials (BOM) and assembly documentation, public on GitHub — anyone who wants a Voron must buy the parts and build it, or buy a kit from a third party that packages that exact BOM.
| Line | Build volume | Mechanics | Sold assembled? |
|---|---|---|---|
| Voron 0 | 120 × 120 × 120 mm | CoreXY, compact frame | No — drawings and BOM only |
| Voron 2.4 | 250³, 300³ or 350 mm (chosen when building) | CoreXY, gantry moves in Z | No — drawings and BOM only |
| Voron Trident | 250³, 300³ or 350 mm (chosen when building) | CoreXY, bed moves down in Z | No — drawings and BOM only |
What matters in the licence column: the Voron-0 and Voron-2 repositories on GitHub both carry the GPL-3.0 licence. It's the same licence family RepRap used two decades earlier — anyone may modify the drawings, reprint, share, or even sell assembled printers based on them, as long as their modifications are published under the same licence.
Prusa: from full GPL to a licence of its own
Prusa Research was once one of the clearest examples of "commercially successful open hardware": the i3 line through the MK3 published design files as OpenSCAD code and KiCad schematics under the GPL, in the RepRap spirit the i3 itself descends from. Prusa's open-source policy page is still there, with a commitment to publish in stages: firmware and printed parts first, electrical schematics and other data later.
CORE One, launched in late 2024, was the turning point. It's an almost ground-up design sharing very little with the old i3 architecture, and at launch it shipped without full hardware files — no design files for the controller board or the Nextruder extruder, just STL files for the printed parts. "Open source" in the announcement referred almost entirely to firmware, not hardware.
| Right | GPL (RepRap, Voron Design) | OCL (Prusa, from 12/2025) |
|---|---|---|
| Download and view the drawings | Yes | Yes |
| Modify for personal use | Yes | Yes |
| Print your own spare parts | Yes | Yes |
| Share modifications publicly | Yes, same licence | Yes, same licence |
| Sell assembled printers based on the drawings | Yes | No, unless separately agreed |
| Third parties packaging kits for sale | Yes, has happened with Voron | Not stated — ask Prusa |
Why "open" matters if you build your own
With a fully open printer like a Voron, the practical benefit isn't that it's "free" — the parts for a Voron usually cost no less than an equivalent assembled printer. The benefit lies in three places: you know exactly what's inside because you chose it, you can replace discontinued parts with equivalents without waiting for a maker, and the community building the same machine is where you look things up when something goes wrong — independent of whether any single company still exists.
But "open" doesn't mean easy
The downside rarely mentioned: nobody is responsible if the machine doesn't work as the drawings promise. There's no warranty for the whole machine, no maker's support hotline, and most of the first week goes into assembly, mechanical alignment and firmware tuning — not printing. It suits people who like fixing things and have the time, not someone who needs a printer working on day one.
How to read a maker's "open" claim
- Which files are actually published? Source CAD files or code (OpenSCAD, STEP, KiCad) are quite different from STL files only — an STL doesn't let you edit the original design.
- What exactly is the licence? "Open" isn't one concept. GPL, MIT, Creative Commons and a self-written licence like Prusa's OCL give different rights — reading the licence name matters more than reading "open source" in an advert.
- May you sell derivative products? This is the biggest difference between the GPL and licences that restrict commercial use. If you plan to package kits for sale, or run a print service based on the drawings, this is the clause to read first, not afterwards.
- The whole printer or just part of it? Many makers publish open firmware but keep the hardware closed, or publish printed parts but keep the controller board closed. A per-category status table — like Prusa's policy page — is more trustworthy than a blanket statement.
Material is still material, open or not
Whether you choose a fully open printer, a kit sold from open drawings, or a boxed machine from a big maker, the material side doesn't change: filament still needs the right drying temperature, the right bed settings for your plate, and the same calibration routine at every spool change — covered in calibrate your printer per spool. A self-built Voron needs a maintenance schedule too; the only difference is you write it yourself instead of reading the maker's — the approach in 3D printer maintenance schedule applies to self-built printers as well.
The GPL doesn't forbid selling assembled printers built from someone else's drawings. That's exactly what a licence like the OCL is written to prevent.
If your goal is just to print parts rather than build a printer yourself, most of the considerations above don't affect your choice — choosing your first 3D printer and 3D printer makers compared are better articles for that.
Frequently asked
Are open-source printers cheaper than assembled ones?
Not really. The parts to build a Voron usually cost as much as or more than an assembled printer in the same class, because you buy quality components individually rather than in a maker's bulk lots. The benefit of an open printer is control and repairability, not price.
Does Voron sell assembled printers?
No. Voron Design only publishes drawings, a bill of materials and assembly documentation. Some third parties package kits or build to order from those exact drawings, but Voron Design itself doesn't manufacture or sell printers.
Since the Open Community License, are Prusa printers still open source?
Depends on the definition. The OCL allows viewing, modifying, printing your own spare parts and sharing modifications — but forbids selling assembled printers or derivative products without a separate agreement with Prusa. By a full GPL-style definition of open source (unrestricted commercial use), the OCL doesn't meet that bar. Prusa calls it its own licence, not the GPL.
Are the older Prusa i3 and MK3 still GPL open source?
The design files for the i3 line through the MK3 were published as OpenSCAD code under the GPL, and that's published history. The clearest change came from CORE One onwards — a new architecture not inherited from the i3, without full hardware files at launch.
Should my first 3D printer be open source?
Usually not, unless you genuinely want to learn mechanical assembly. An open printer means diagnosing faults yourself, sourcing replacement parts yourself, and no manufacturer support for the whole machine. For a beginner, an assembled printer with technical support usually saves a lot of time — covered in detail in choosing your first 3D printer.