How much filament does a color change waste?
This guide was drafted with AI assistance.
Each filament change flushes a fixed amount of plastic, commonly around 0.35 g of PLA for a dark-to-light change. The total is that times the number of changes, and the number of changes is set by how many layers two colors share, not by how much of the model is painted. The same 5 mm stripe costs about 9 g painted around a 100 mm vase and about 174 g painted up it. Turn the model, flush into infill, or print the colors as separate parts and there is nothing to flush at all.
Where the waste goes
A single nozzle can only hold one filament. When a layer needs a second color, a multi-material printer pulls the first filament back, loads the next one and pushes plastic through the hot end until the old color is gone from the melt. That purged plastic is the waste: on Bambu printers it drops out of the back as the familiar "poop", on others it goes into a wipe tower. On top of the flush, most setups print a prime tower next to the model, a small column that gets a little of every layer so each new color starts cleanly.
How much is flushed is a slicer setting, set per pair of colors. Bambu Studio and OrcaSlicer keep a table of flushing volumes for every from/to pair and fill it from the filament colors: going from a dark color to a light one needs the most, because the last traces of dark show in light plastic; going the other way needs much less. A figure often quoted for Bambu Studio's default is 280 mm³ per change, and light-to-dark changes are commonly set around 100 to 150 mm³. Check your own table: it is under the flushing volumes button next to the filament list.
The arithmetic
Everything below comes from one line:
PLA is about 1.24 g/cm³, so 280 mm³ is 0.35 g per change and 150 mm³ is 0.19 g. The prime tower comes on top and is not counted here.
The number of changes is the part people guess wrong. A slicer orders the colors on each layer so the next layer starts with the filament it just finished, so a layer with two colors costs about one change, a layer with three costs about two, and a layer with one color costs nothing. Add that up over every layer and you have the count.
Waste follows layers, not area
That is why two models with the same amount of paint can differ by a factor of twenty. What counts is how many layers contain more than one color. At 0.2 mm layer height, every millimetre of height where two colors meet is five changes.
- Paint that runs up the model (a vertical stripe, a zip on a jacket, a line down a figure's back) touches every layer it spans. Cheap to paint, expensive to print.
- Paint that stays within a band of height (a belt, a hat brim, eyes, text on a top face) touches only a few layers, however wide it is.
- Colors stacked by height (a white base under a red top) cost one change at the border and nothing else. That is the case a manual layer swap handles with no multi-material unit at all.
Worked examples
All at 0.2 mm layers, PLA, two colors per layer where they meet, prime tower not included:
| Model | Layers where colors meet | Changes | At 150 mm³ | At 280 mm³ |
|---|---|---|---|---|
| 100 mm vase, 5 mm stripe painted around it | 25 | 25 | 4.7 g | 8.7 g |
| Same vase, 5 mm stripe painted up it | 500 | 500 | 93 g | 174 g |
| 55 mm painted mushroom: red cap, cream stem, six white spots | 26 | 26 | 4.8 g | 9.0 g |
The mushroom is the example file in our 3MF color splitter, measured by slicing its paint into 0.2 mm layers: its spots sit near the top of the cap, so only 26 of its 276 layers have two colors. The vase rows are the arithmetic above. Nothing about the stripe changed between them except its direction.
Five ways to waste less
Turn the model
If you can print a model on its side so a long color border runs flat instead of up, do it. It is the only change that cuts waste without costing anything else, and for a stripe it is the difference in the table above.
Flush into something useful
Bambu Studio and OrcaSlicer can push part of the flush into the model's infill, into support, or into a spare object you print on purpose, instead of out of the back. Bambu describes the options in its wiki on reducing waste during filament change. Infill only takes it where the infill is hidden, so it helps most on big, solid-ish parts.
Tune the flush table
Light-to-dark changes rarely need the default. Lower those pairs, print a test, and look for streaks; keep dark-to-light where it is. A flush multiplier below 1.0 trims every pair at once, at the risk of a tinted first line after each change.
Group colors by height
If you are designing the model, put color changes on horizontal lines where you can: a band, a base, a cap. Colors that only stack by height need no multi-material unit at all, just a pause and a swap.
Print each color as its own part
A part in one color has no changes, so no flush and no prime tower. The 3MF color splitter turns a painted 3MF into single-color parts that fit back together: flat borders are cut with an alignment pin, painted details become inlays that slide into pockets. It costs a few minutes of gluing and a hairline seam at each color border, and for the vase with the vertical stripe it saves the full 174 g.
Common questions
How much filament does one color change waste?
One flush. Slicers set it per color pair; around 280 mm³ is the figure most often quoted for a dark-to-light change in Bambu Studio, which is about 0.35 g of PLA. Light-to-dark changes need less. The total is that amount times the number of changes, plus the prime tower.
Why does my small multicolor print waste more filament than the model weighs?
Because the waste follows the number of layers where two colors meet, not the size of the painted area. A thin detail that runs the full height of the model forces a filament change on every layer, and at 0.2 mm layers that is five changes per millimetre of height.
How can I reduce purge waste?
Turn the model so color borders run horizontally, flush into infill or a spare object, tune the flush volumes for light-to-dark changes, group colors by height and use layer swaps, or print each color as its own part so there are no changes at all.
Made by meshcast.app. The flush volumes above are typical settings, not measurements of a specific printer; your slicer's own table is the number to use.