Slicing for a Bambu Lab printer without Bambu Studio: the .gcode.3mf explained

Three kinds of file with 3MF or G-code in the name

Own a Bambu Lab printer and you will meet three file types:

• .3mf: a model or a project. It holds the geometry, and often settings and plate layouts, but no G-code. It still has to be sliced.
• .gcode.3mf: a sliced plate. It holds the finished G-code for one plate, with preview images and the settings it was sliced with. This is what Bambu Studio writes when you export a sliced plate, and what the printer prints.
• .gcode: plain G-code, a text file. It is what most other brands' printers run.

The double extension is the point: .gcode.3mf means sliced and ready to print; .3mf on its own means not yet.

What is inside a .gcode.3mf

Every 3MF file is a ZIP archive. Copy a .gcode.3mf, rename the copy to .zip and open it: in the Metadata folder you find the G-code itself (plate_1.gcode for the first plate), PNG previews of the plate, and configuration files that record the printer, the filament, the estimated time and weight, and the full set of settings used. The printer's screen and Bambu's apps read them to show the preview, the print time and the filament before you start.

Renaming a .gcode.3mf to .gcode does not turn it into plain G-code. The G-code is inside the archive.

Why a Bambu printer wants the 3MF version

Bambu Lab built its workflow around this container: the slicer exports it, the cloud and Bambu Handy send it, and the printer's screen lists it with its preview. Plain .gcode is the norm on other brands; on a Bambu printer, the .gcode.3mf is the file that behaves the way the printer and its apps expect. A slicer that targets Bambu printers has to produce it.

Making one without Bambu Studio

Two options produce a .gcode.3mf for a Bambu Lab printer:

• OrcaSlicer on a computer. It began as a fork of Bambu Studio, supports Bambu printers with their own presets, and exports the same kind of sliced file.
• An online slicer in the browser. SpeakCAD's online slicer runs the unmodified OrcaSlicer command-line slicer with the presets bundled with OrcaSlicer, Bambu Lab's among them. Pick Bambu Lab, the model and the nozzle, and the download is a .gcode.3mf. Nothing to install, so it works on a Chromebook, an iPad, a phone or a work computer.

The Bambu Lab models in the list include the A1, the A1 mini, the P1S, the X1 Carbon and the H2D. The print profiles are Bambu's own, named the way Bambu Studio names them (0.20mm Standard, for example), and the filament list includes Bambu's filaments as well as generic ones.

In the online slicer:

1. Drop the STL or 3MF on the page (up to 50 MB). It opens in 3D first.
2. Choose Bambu Lab, your model, and the nozzle that is installed.
3. Pick the print profile, the material and the filament, Bambu's own or generic.
4. Set infill, walls, supports and adhesion, or leave the defaults.
5. Click Slice and download. You get the .gcode.3mf with the print time, the filament in grams and meters, the layer count and whether supports were used.

Sending it to the printer

The microSD card

The simplest route, and it works with the printer offline. The A1, A1 mini, P1 and X1 series take a microSD card; check the manual for newer models. Copy the .gcode.3mf to the card, put the card in the printer, choose the file on the printer's screen and start it. Keep the full name ending in .gcode.3mf; if a phone or a browser renamed the download, restore it.

Bambu Handy

Bambu Handy is Bambu Lab's phone app for printers bound to your Bambu account, and it can start prints on them. Whether it opens a .gcode.3mf shared from the phone's files depends on the app version, so try it once with a small file. When it does, the whole trip happens on the phone: slice in the browser, open the download with Bambu Handy from the Files app or the Share sheet, pick the printer, print.

The local network

Bambu printers can work through Bambu's cloud or in LAN-only mode, where a computer on the same network connects with the access code shown on the printer's screen. Bambu Studio and OrcaSlicer both send jobs that way. Bambu Lab has changed which third-party tools may talk to its printers over the network, so if a tool stops connecting after a firmware update, check Bambu's current notes on LAN mode. For a file from the online slicer, the card or Bambu Handy is the simpler route.

What the online slicer does not do on a Bambu

• Multi-color with the AMS. The file is single-material: no painted colors, no color changes. If your printer has an AMS, choose the spool that feeds it when you start the print, as with any single-color file.
• The desktop extras. A layer-by-layer preview, custom start G-code, variable layer height and modifiers need Bambu Studio or OrcaSlicer on a computer. Online slicer vs desktop slicer lists the rest.

Common snags

• The printer warns about the model or refuses the file. It was sliced for another model, an A1 file on an A1 mini for example. Slice it again with the right one.
• A different nozzle is installed. If you swapped to a 0.2 or 0.6 mm nozzle, choose it in the slicer too: every line is planned for the nozzle you select.
• The name lost its .gcode part. Rename it to end in .gcode.3mf again; the double extension is how you tell a sliced file from a project at a glance.

Slice for your Bambu printer in the browser. The online slicer gives every account 1 free slice, its first (a free account, no card). After that, a slice uses one slice from a Slicer pack (20 slices for $3, once, never expire) or 5 credits, and slicing is included in Pro and Unlimited. Re-slicing the same file with other settings within 10 minutes is free.

If the model needs changing before it is worth printing, SpeakCAD's AI editor can rebuild the STL as an editable model and give you the .gcode.3mf for your Bambu printer from the same page.