How to assign filaments to the left and right nozzle

Choose Custom grouping mode in Bambu Studio and move each filament to the left or right nozzle. Then load every spool into the AMS (Bambu Lab’s Automatic Material System spool changer) paired with that nozzle. On a stock H2D, H2C or X2D, a nozzle cannot reach spools in the other nozzle’s AMS.

How do you assign filaments to the left and right nozzle?

In Bambu Studio, open the menu on the Slice button and pick a grouping mode. Custom lets you put each filament on the left or right nozzle yourself. Filament-Saving and Convenience group them automatically. Without a Filament Track Switch, each nozzle only draws from its paired AMS, so put every spool in the matching AMS.

There are two separate assignments. In the slicer, each filament goes to the left or right nozzle. At the printer, each AMS is paired with one nozzle. When the two disagree, the job cannot use that spool until you move it into the right AMS. PrusaSlicer, OrcaSlicer and Cura skip the grouping step. There you give each object or support feature an extruder number, and the table further down lists the menus.

How to assign filaments to the left and right nozzle in Bambu Studio

1. Pair each AMS with a nozzle. On the printer screen, go to Filament, then AMS Setup. Auto Mode detects the side from a test feed. Manual Mode lets you pick left or right. On the H2D, the upper PTFE (polytetrafluoroethylene) tube coupler feeds the right extruder and the lower one feeds the left.
2. Sync the AMS to Bambu Studio. Syncing tells the slicer which filaments each nozzle can reach. With no AMS connected, Bambu Studio assumes each nozzle takes one filament from an external spool.
3. Give each part its filament. Right-click an object or part and choose Change Filament. For dedicated support material, set Support/raft base and Support/raft interface on the Support tab.
4. Pick a grouping mode. Open the menu on the Slice button and choose Filament-Saving, Convenience or Custom (or Quality on the X2D). In Custom, click a filament icon or the exchange button to move it to the other nozzle.
5. Slice and check the Filament Grouping panel. Compare it with the spools in each AMS. If a filament sits on a nozzle whose AMS does not hold it, move the spool, or click Regroup filament and change the split.
6. Send the job and map the spools. Each sliced filament can only be matched to a spool on its assigned nozzle. That holds even when the other nozzle’s AMS has a closer color.

Grouping can be set per plate. The grouping icon at the right of each plate opens that plate’s settings. When you slice all plates at once, the mode chosen on the Slice button applies to every plate and overrides the per-plate choices. Switch to single-plate slicing to keep a different grouping on one plate.

What do the filament grouping modes do?

Bambu Studio has three grouping modes on every dual-nozzle printer and a fourth on the X2D:

Mode	How it groups	Default?
Filament-Saving	Puts the filaments that share the most layers and need the largest flushes on different nozzles	Yes
Convenience	Matches the slice to the spools already in each AMS, by material type and then color	No
Custom	You place each filament on the left or right nozzle	No
Quality (X2D only)	With a support filament set, the right auxiliary nozzle prints only supports and the left nozzle prints the part	No

Filament-Saving weighs four things, in this order:

1. Filaments a nozzle cannot print
2. The number of slots in the AMS on each nozzle
3. Flush volume
4. Color match to the loaded spools (Delta E)

Flush volume outranks color, so the grouping can differ from where your spools already sit. Check the Filament Grouping panel after every slice. Filament-Saving can also produce more filament changes than Convenience or Custom, because it counts only waste.

Bambu Lab suggests Convenience when you start a job remotely and cannot move spools. Re-sync the AMS before you slice. Convenience wastes more filament on flushing.

Which AMS feeds the left nozzle and which feeds the right?

Whichever one you paired with it in AMS Setup, and each AMS feeds only one nozzle. Auto Mode sends filament from the AMS until a Hall sensor on the left or right extruder triggers. For Auto Mode, load at least one spool and unload anything already in the extruder.

Use Manual Mode when the AMS is empty. Once an AMS has fed filament into an extruder, its icon turns gray and the pairing is locked until you unload. Auto-refill also follows the pairing: a backup spool only takes over from a spool in an AMS on the same nozzle. The H2D dual nozzle page lists how many AMS units each nozzle accepts and when you need the 4-in-1 PTFE adapter.

On the H2C, Bambu Lab’s FAQ recommends using both the left and right hotends for two-color prints. A left-to-right switch skips the AMS unload and reload, so the print finishes sooner than with two hotends on the right side.

Which filaments can only go on one nozzle?

Bambu Studio applies these rules before it weighs flushing or color, so they override the grouping mode:

Rule	Printer	Priority
TPU (flexible thermoplastic polyurethane) on the left nozzle locks out the right nozzle, because the left nozzle’s up-and-down motion twists TPU. TPU on the right nozzle can run alongside a rigid filament on the left.	H2D	High
TPU cannot print from the left nozzle	H2C	High
PPA-CF and PPS-CF (carbon-fiber-filled polyphthalamide and polyphenylene sulfide) print only from the left nozzle	H2D	High
A part taller than 320 mm goes to the right nozzle	H2D	Medium
A part placed in the left-only or right-only strip of the bed goes to that nozzle	H2D	Medium
A filament either nozzle can print goes to the right nozzle	H2D	Low

The X2D’s two nozzles are not identical. The left is the main hotend with a direct-drive extruder. The right is an auxiliary hotend fed by an extruder on the rear panel.

Bambu Lab’s X2D FAQ lists TPU for AMS among the main hotend’s supported filaments but not the auxiliary’s, and says to print TPU from the main hotend. The auxiliary hotend is limited to 200 mm/s and an acceleration of 1,000 mm/s², and its print area is 235.5 × 256 × 256 mm, against 256 × 256 × 260 mm for the main hotend. Printing TPU and PETG in one job and water-soluble PVA supports on a dual nozzle printer walk through two common splits.

How does the Filament Track Switch change nozzle assignment?

It removes the fixed pairing. With the switch fitted, any AMS slot can feed either nozzle, so a filament grouped to the left nozzle no longer has to sit in the left AMS. One AMS can even feed both nozzles, but only one at a time: the AMS unloads one filament before it loads the next.

The switch also enables dynamic mapping, where Bambu Studio moves a filament to the other nozzle partway up the print. On the Prepare page, click the Edit Filament Grouping icon. Choose Fila Saving mode, tick Enable Smart Filament Assign and click OK. “L R” in the nozzle mapping list marks a filament that both nozzles will print.

After slicing, Bambu Studio recommends which filaments to load in separate AMS units. A change between filaments on different switch inlets is faster than a change on the same inlet.

The switch takes no external spool, so remove it for jobs that run from one. Bambu Lab’s X2D guide also rules out filaments the AMS does not support. Its list includes TPU and fiber-filled PA6 (nylon), PET (polyester), PPA and PPS. The Filament Track Switch page has the firmware versions, installation and limits.

How do you assign extruders in PrusaSlicer, OrcaSlicer and Cura?

You give each object or part an extruder number, and you set the support extruders separately. These slicers have no grouping step:

Task	PrusaSlicer	OrcaSlicer	UltiMaker Cura
Assign an object or part	Double-click the colored box in the object list, press the extruder’s number key, or right-click and choose Change extruder	Right-click and choose Change Filament	Right-click and choose an extruder under Print Selected Model With
Support body	Print Settings, Multiple Extruders: Support material/raft/skirt extruder	Support/raft base	Support Extruder, then Support Infill Extruder
Support interface	Support material/raft interface extruder	Support/raft interface	Support Interface Extruder (or Support Roof and Support Floor Extruder)
Leave support unassigned	0 uses the current extruder	“Default” uses the current filament	Not listed

PrusaSlicer shows the object list only in Advanced or Expert mode. Its Multiple Extruders page also sets separate extruders for perimeters, infill, solid infill and the wipe tower. Cura shows its support extruder settings only when the printer profile has more than one extruder and the second one is enabled.

For a two-color model exported as separate files, align the bodies before you assign them. In Cura, select both and choose Merge models from the right-click menu. The shortcut is Ctrl+Alt+G, or Cmd+Option+G on a Mac. Cura aligns the bodies by the origins they were modeled with.

How do you use a dual extruder 3D printer?

Load both nozzles, tell the printer where they sit, then tell the slicer which filament goes where:

• Load and pair. Feed each nozzle from its own AMS or external spool and pair them as above.
• Calibrate the offset. The printer has to know where the second nozzle sits relative to the first. Dual nozzle offset calibration covers Bambu Lab, Klipper and Marlin machines.
• Assign and slice. Group the filaments, or set extruder numbers, using the steps on this page.
• Leave the prime tower on. Bambu Lab says a switch can leave residue on the nozzle, and the tower cleans it off and steadies the pressure before the nozzle returns to the part. Stopping dual nozzle ooze deals with stringing from the idle nozzle.
• Keep two-material parts where both nozzles reach. The H2D’s dual-nozzle print volume maps the shared area.

Why can’t I pick a spool when sending the print?

Because the slice grouped that filament to the other nozzle, and its spool sits in an AMS paired with the wrong side. Bambu Studio will not cross nozzles in the send window. You can fix it three ways:

• Move the spool into an AMS on the nozzle the slice expects. This keeps the Filament-Saving grouping.
• Re-slice in Convenience mode after re-syncing the AMS, so the grouping follows the spools.
• Re-slice in Custom mode and move the filament to the nozzle that already holds its spool.

If Bambu Studio keeps putting a filament on a nozzle you did not choose, check the rules table above. A part in a single-nozzle strip of the bed or over 320 mm tall is forced onto one nozzle. On the H2D, TPU on the left takes the right nozzle out of the job.