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ThetaSigma Labs
ThetaSigma Labs

·1061 words·5 mins

Setting Up a Single Extruder as a Multi-Extruder in PrusaSlicer
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Printer: Prusa Core One L Slicer: PrusaSlicer Use case: Flush inlay lettering (black body with white letters) using a manual filament swap Status: Verified working

Purpose
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PrusaSlicer has two workflows for two-color prints on a single-nozzle printer:

  1. Color Change — uses the layer slider and the + icon. Inserts M600 directly. Best when every layer is one color only.
  2. Single Extruder Multi Material (multi-extruder mode) — assigns parts of the model to “extruder 1” and “extruder 2”. This is needed when a feature must be split out by object or modifier, not just by Z height.

This note covers Option 2, because the lettering inlay was set up as a separate object/modifier and assigned to a second extruder.

Out of the box, Option 2 does not work on a single-nozzle printer:

  • The slicer outputs T0 / T1 tool change commands, which the Core One firmware ignores
  • A purge tower is generated and printed, wasting time and filament
  • The printer never pauses to ask for a filament swap

The steps below fix all three problems.

Model Design Requirements
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  • First layer height: 0.2 mm
  • Insert depth: 2 layers (0.4 mm total at 0.2 mm layer height)
  • The inlay region must be modeled flush with the surrounding surface so the white filament fills the recess

PrusaSlicer Setup Steps
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Do these in order. Each one matters.

1. Configure the printer for two extruders
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  • Open Printer Settings tab
  • Go to General in the left sidebar
  • Set Extruders = 2
  • Check Single Extruder Multi Material

2. Add M600 to the Tool change G-code
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  • Still in Printer Settings, go to Custom G-code in the left sidebar
  • In the Tool change G-code field, type:
M600 ; Filament change

Important: this must go in Tool change G-code, not in Color Change G-code. The Color Change field only fires when an “Add color change” marker is placed via the layer slider. The Tool change field is what fires when the slicer emits a T0 or T1.

3. Fix the Single Extruder MM setup numbers
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  • In Printer Settings, go to Single extruder MM setup
  • Set:
    • Cooling tube position = 10
    • Filament parking position = 0
    • Extra loading distance = 0

The default values in this section are tuned for a real MMU and cause a large blob during manual swaps. These numbers stop that.

4. Disable the wipe tower
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  • Open Print Settings tab
  • Go to Multiple Extruders in the left sidebar
  • Under Wipe tower, uncheck Enable
  • Also uncheck Prime all printing extruders if it is ticked

5. Save the profile
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  • Click the small disk icon next to the printer profile name at the top

  • Save as a custom name (for example Core One L — manual two-color)

  • Prusa system profiles cannot be overwritten, so this must be a custom profile

  • Repeat for the print profile if any Print Settings were changed

6. Force a re-slice
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  • Click (Re)Slice Now in the bottom-right of the Plater
  • Do not rely on the cached slice — settings changes are not always reflected until the slice is forced

7. Assign filaments
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  • In the Plater, the right-hand filament dropdowns now show two slots
  • Set both to the filament type you are printing (for example PLA + PLA)
  • Set the color of each slot to match the real filament you will load
  • Verify your object or modifier is assigned to extruder 2 for the inlay region

Verifying the G-code (Debug Step)
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The first time the project is set up, switch to text G-code so the file can be opened in a text editor.

Switch to text G-code
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Two options:

  • Per profile: Printer Settings → General → uncheck Supports binary G-code, then save the profile
  • Globally: Configuration → Preferences → Other → uncheck Use binary G-code when the printer supports it

Re-slice. The export will now be .gcode instead of .bgcode.

What to search for in the file
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Search termWhat it meansExpected count for a single inlay
M600Filament change pause1 or 2 (one swap to white, optional swap back)
T0, T1Tool change commandsSame count as M600 — each should sit right before an M600
WIPE_TOWER or CP TOOLCHANGEWipe tower commentsShould be zero if the wipe tower is properly disabled

Sanity check in the preview
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  • In PrusaSlicer after slicing, the layer slider on the right shows pause icons at each M600
  • Confirm the icons sit at the Z heights where the filament should swap

Switch back to binary G-code
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Once the file is verified, re-enable binary G-code:

  • Per profile: re-check Supports binary G-code, save profile
  • Globally: re-check Use binary G-code when the printer supports it

Binary G-code is smaller and uploads faster to the printer.

Known Quirks on the Core One
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  • Door interlock during M600: The print head will not move while the door is open. The standard “hold the purge string and let the nozzle pull it off” trick from MK3/MK4 days does not work. Close the door before resuming. There will be a small ooze blob on the next move.
  • Possible “bonus” M600 pauses: Some users on GitHub report extra filament-change prompts at unexpected points. Verify with the G-code search before a long print.
  • Open feature request (March 2026): Prusa is considering a proper single-extruder purge tower for M600 prints. May simplify this workflow in a future PrusaSlicer release.

When to Use Color Change Instead (Option 1)
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If the inlay design has every layer as one color only (no layer has both black and white), the simpler workflow is:

  1. Slice the model with one filament
  2. Drag the layer slider to the layer where white should start
  3. Click the orange + icon → Add color change
  4. Repeat at the layer where black should resume

No multi-extruder setup, no wipe tower, no Tool change G-code edit. Use this when the geometry allows it.

Sources
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