TL;DR: The flushing volume is how much filament the printer purges on every color swap. Set it too low and the old color bleeds across the boundary; too high and you waste filament and time. Print a flush calibration test exactly as its author sets it up, read where each color change goes clean using the test's own formula, and type those per-pair numbers into the Flushing volumes table in Bambu Studio or OrcaSlicer. Below: why painted 3MFs feel this more than most prints, the five-step calibration, and how to read the result.
Why does a painted 3MF need its own flushing-volume pass?
A painted 3MF assigns a color to every triangle, so a figure with eyes, trim, and a base can trigger dozens of filament swaps over its height. Every swap purges the old color out of the nozzle before the new one prints. If the purge volume is too small, the previous filament hasn't fully cleared and it streaks into the first millimeters of the new region. That reads as bleed at a boundary you painted sharp. Calibrating the volume once fixes it across the whole print, and usually trims waste at the same time.
This is the print-time half of clean boundaries. The mesh-side half, keeping the painted edge crisp before the slicer ever sees it, is covered in stopping multi-color paint from bleeding past your edges. You want both: a sharp edge on the model, and enough purge at the swap to honor it.
Step 1 — Read the swap count in Layerpaint first
Before you touch the slicer, open your model in the painter and turn on Show swap bar in the Layers panel. The bar counts total filament swaps and shows where they stack up by layer. A high count means you'll be flushing a lot, so the per-swap volume matters more.
The Flush volume field next to it is an estimate, not a control. It multiplies your swap count to show roughly how much filament the job will burn. Set it near whatever your slicer actually uses and you'll get a realistic waste figure. If the count looks brutal, reorder your palette before exporting; reordering the palette cuts swaps before flush volume even enters the picture.
Step 2 — Print the flush test as its author sets it up
Grab a flush calibration model with clear instructions. One example is AMTprojects' Flushing Volumes Calibration – V2 and new Gcode on MakerWorld. Read its "Dialing in flushing volumes" section before you print. For that test, the author starts from a flush of 100 mm³ with a 1.00 multiplier, uses the stock filament-change G-code, and asks you not to change the other settings. It is not a zero-purge test, so don't set your volumes to 0.
Save and close your painted project first, then open the test as its own project so its settings never leak into your real print. Assign the same spools you'll print your model with and check the sliced preview. Each band of the test prints a color change and adds a further 250 mm³ of flush, so you can see where the new color comes through clean.
Use the actual filaments from your AMS, MMU, or CFS, not stand-ins. A matte dark filament bleeding into a light one needs far more purge than two similar mids, so testing the wrong pair gives you a number you can't trust.
Step 3 — Read where each transition goes clean
Look at each band and find the height where the new color stops carrying any of the old one. Work out the value with the formula in the test's instructions, including its starting flush, rather than guessing from the band. If the result is hard to read, print the test again; don't pick a low value just to shrink the waste estimate.
Direction matters. Dark into light usually needs more purge, because any leftover dark shows; light into dark often needs less. Don't assume the two match: record black → white and white → black as separate numbers, along with the spool names, nozzle and slicer version.
Step 4 — Enter the values in the Flushing volumes table
Close the test and reopen your painted project. In Bambu Studio or OrcaSlicer, find the Flushing volumes button in the project filament panel and open the table. Bambu's wiki on reducing filament-change waste documents how the defaults are computed. It's a grid of every from → to color pair, with a global Multiplier above it. Set the multiplier to 1.00 so it isn't scaling your measured values, then type each calibrated value into the matching from → to cell. Leave pairs you didn't test at their normal values.
If you'd rather not redirect the purge into a tower, that's a separate setting: flush into objects and infill hides most of it inside the part. Calibrated volumes and flush into infill stack: dial the volume down here, then route what's left into the model.
Step 5 — Reslice and confirm the boundaries
Reslice your painted 3MF with the new table and check the color assignments in the preview. Before a long job, print a small sample that uses both directions and look for traces of the old color in the new one. If you see any, raise the affected value. A lower waste estimate on its own doesn't prove the print will look clean.
In Bambu Studio the flushing table and multiplier are project settings, not part of a filament preset. Save the project as a 3MF to keep them, and check the table again after a fresh import or a filament change. Keep your written record of the numbers as a backup.
Common questions
Does Layerpaint set the flushing volume in the exported 3MF?
No. Layerpaint paints the colors and exports a Standard 3MF; flushing volumes are a slicer setting you tune after import. The Flush volume field in the Layers panel is only an estimate that feeds the waste readout on the swap bar. It doesn't change the exported file.
Will lower flushing volumes cause color bleed?
Below the calibrated number, yes. That's the whole point of testing rather than guessing. At the clean-transition value your test gives, the boundary should stay sharp; confirm it with a small sample print before a long job.
Do I have to recalibrate for every filament set?
Recalibrate when you change a filament's color or finish. A matte black behaves differently from a silk black, and a brand-new pairing you haven't tested is a guess. Same filaments in a different palette order are fine. Only the from/to relationships you actually print need numbers.
Does this work for Prusa MMU3 and the Anycubic ACE Pro or Creality CFS?
The idea is universal: every multi-filament system purges on a swap. PrusaSlicer has its own Purging volumes dialog under the wipe-tower settings, with the same from/to grid, and the OrcaSlicer-based slicers for the ACE Pro and CFS carry the same Flushing volumes table as OrcaSlicer.
Try it now
Layerpaint is free to try — no account, no install, no upload. Paint your model on the painter, watch the swap bar, and export when you're ready. Your first export is free, then $6.97 for 10 exports or $39.97 unlimited. No subscription.
Happy printing. 🎨