PrintHive

Slicer Tips: Understanding and Optimizing Flushing Volumes

What are Flushing Volumes?

When printing with multiple colors or materials (multicolor/multimaterial prints), your printer must change filaments during the print. Each time the printer switches from one filament to another, a small amount of the old filament remains in the extruder and nozzle below where the filament cutter makes its cut.

Flushing (also known as purging) is the process where the extruder pushes out the old filament through the nozzle until only the new filament is being extruded. This purged filament is extruded in an area next to the build plate and then directed away from the print area.

The Flushing Volume determines how much material must be extruded during each filament change. This volume varies depending on the relationship between the 'from' filament and the 'to' filament.

Why Flushing Volume Matters

  • Color transitions: Darker colors need higher flush volumes to switch to lighter colors, while lighter colors need less to switch to darker colors
  • Material properties: Support filaments require specific flushing volumes to prevent contamination
  • Print quality: Too little flushing results in discolored layers; too much wastes time and material
  • Cost efficiency: Optimizing flushing volumes can significantly reduce material waste

Accessing Flushing Volumes in Bambu Studio

To view and manage flushing volumes in Bambu Studio:

  1. Open your project in Bambu Studio
  2. Locate the Project Filaments section
  3. Click the Flushing Volumes button
Flushing Volumes button in Bambu Studio Project Filaments section

The Flushing Volumes button in the Project Filaments section

This opens a dialog showing the flushing volume matrix for all filament pairs in your project.

Flushing Volumes dialog showing the matrix and multiplier settings

The Flushing Volumes dialog with matrix and controls

Understanding the Flushing Volume Matrix

The flushing volume matrix is a table that shows how much material (in mm³) needs to be flushed when changing from one filament to another.

Reading the Matrix

  • Rows represent the "from" filament (the filament currently in the nozzle)
  • Columns represent the "to" filament (the new filament being loaded)
  • Values show the flushing volume in mm³ for each transition
  • Diagonal cells (from 1→1, 2→2, etc.) show 0 because no change is needed

Auto-Calculate vs Manual Adjustment

Bambu Studio uses an algorithm to auto-calculate required flushing volumes based on:

  • Filament colors (darker to lighter requires more)
  • Material properties (support materials, compatibility)
  • Best practices for print quality

Adjusting Flushing Volumes

Global Multiplier

The easiest way to adjust all flushing volumes at once is using the Multiplier field:

  • 1.00 = Default calculated values (100%)
  • 0.90 = 10% less flushing for all transitions
  • 0.80 = 20% less flushing for all transitions
  • 1.10 = 10% more flushing for all transitions

Recommended approach

Start with a multiplier of 0.8 or 0.9 for initial testing. The default values are slightly conservative to ensure quality, so you can often reduce them without issues.

Individual Pair Adjustment

For fine-tuning, you can edit individual values in the matrix:

  1. Click on any cell to edit the specific from→to transition
  2. Enter your desired flushing volume in mm³
  3. Test print to verify the results

Note: The suggested range is typically [63, 900] mm³. Values outside this range may cause issues.

Re-calculating Values

If you manually edit values and want to return to defaults:

  • Click the Re-calculate button to restore all auto-calculated values
  • This will override any manual adjustments you've made

Tips and Best Practices

Testing Approach

  1. Start conservative: Use default values (1.0 multiplier) for your first print
  2. Reduce gradually: Try 0.9, then 0.8 multiplier on test prints
  3. Watch for issues: Inspect layers carefully for discoloration
  4. Fine-tune individually: Adjust specific problematic transitions

Signs of Incorrect Flushing Volumes

Too low (under-flushing):

  • Visible discolored streaks or patches
  • Color bleeding between sections
  • Unexpected color mixing in single-color areas

Too high (over-flushing):

  • Excessive material waste
  • Longer print times
  • No quality benefit over lower volumes

Filament-Specific Considerations

Transparent/Light filaments:

  • Require more flushing when transitioning FROM dark colors
  • Need less when transitioning TO dark colors

Dark filaments:

  • Require less flushing overall
  • Can hide minor contamination better

Support materials:

  • Follow recommended values to maintain proper separation
  • Don't reduce below manufacturer suggestions

Advanced Techniques

  1. Color sequencing: Organize print layers to minimize difficult transitions (light→dark→light)
  2. Test prints: Create small test objects with critical color transitions
  3. Documentation: Keep notes on successful multiplier values for your common filament combinations
  4. Material groups: Test and document flushing volumes for your frequently used filament sets

Related Resources

Need Help?

If you're experiencing issues with multicolor prints or flushing volumes, consider:

  • Reviewing your filament compatibility
  • Testing with a simple two-color calibration cube
  • Consulting the Bambu Lab community forums
  • Checking if your specific filament brand has recommended values