AMS Purge Waste Calculator
Figure out how much filament your Bambu AMS (or similar multi-material system) is actually wasting on color changes. For multi-color prints, purge can easily exceed the weight of the part itself, and most filament cost calculators ignore it entirely.
How this works
Every color change on a Bambu AMS, Prusa MMU, or Mosaic Palette requires purging the old color out of the hotend. The material that gets flushed is wasted. For a print with 40 color changes at 8 grams per swap, that's 320 grams of filament dumped into the purge tower, which is roughly $6 of PLA or $10 of PETG.
Most hobbyists never calculate this. Bambu Studio shows flush data but buries it in the preview panel. This tool surfaces the real cost of multi-color printing so you can decide whether it's worth it for a given part.
For the full breakdown of when AMS is worth it, when it isn't, and how to cut purge waste by 30 to 50% without buying extra hardware, read the companion guide: Is multi-color 3D printing actually worth it?
The formula in detail
purge_waste_g = swaps × purge_per_swap_g × flush_multiplier
total_material = part_weight + purge_waste
Worked example. A two-color phone case: 92 g part weight, 38 color swaps, 8 g per swap (Bambu default), flush multiplier 1.0.
- Purge waste: 38 × 8 × 1.0 = 304 g
- Total material: 92 + 304 = 396 g
- At $22/kg PLA: 396 / 1000 × 22 = $8.71 instead of the $2.02 the part alone would cost
The purge waste is more than 4x the part weight. This is the part most cost calculators silently miss. Multi-color isn't free; it's a serious material multiplier.
Purge per swap by system
| System | Default purge per swap | Tunable down to |
|---|---|---|
| Bambu AMS (X1C, P1S) | 7-9 g | 3-4 g (compatible colors) |
| Bambu AMS Lite (A1) | 8-10 g | 4-5 g |
| Prusa MMU2/MMU3 | 15-25 g | 10-15 g |
| Mosaic Palette 3 Pro | ~6 g equivalent | 3-4 g |
| ERCF / 3MS (DIY Klipper) | 5-12 g | 2-4 g (well-tuned) |
The Bambu AMS isn't the worst here. Prusa MMU historically purges much more per swap. Bambu's lighter purge is one reason their multi-color experience feels cheaper to use.
When multi-color is worth the waste
- Big parts, few swaps. A 500 g print with 8 swaps wastes 64 g on purge (13% overhead). Acceptable.
- Color is the entire point of the part. Articulated dragon, hueforge portrait, custom logo plaque. The color IS the value.
- Parts you cannot easily paint. Embedded interior color, mechanical articulation that paint would clog, layer-shifted surface effects.
Not worth it: small parts (under 100 g), prints where you could paint the color in afterward in 10 minutes, and parts where the color is purely cosmetic and the buyer doesn't care.
How to cut purge waste 30 to 50% (free, no extra hardware)
- Lower the flush multiplier. Bambu Studio default is 1.0. Tuned users go to 0.5 to 0.7. Lower means more chance of color bleed in the first layers after a swap, but the savings are real.
- Use the Flushing volumes matrix. Bambu Studio > Filament > Flushing volumes lets you set different purge amounts for each color pair. Light to light colors flush less than light to dark.
- Purge into the model. Enable "purge into infill" or "purge into object" in slicer settings. The flushed material goes into hidden internal structure instead of a separate purge tower. Reduces visible waste even if total material is similar.
- Group same-color features. Slice your model so all the white parts print in one batch, then all blue, then all red. Cuts swap count drastically.
- Use the Bambu sponge. The little sponge clip on the AMS reduces purge needed for certain color transitions. Worth a small amount.
Frequently asked
- Why does Bambu AMS waste so much filament?
- Every time the printer changes colors, it has to flush the previous color out of the hotend before the new color prints cleanly. Bambu's default flush is around 8 grams per swap. A print with 40 color changes wastes 320 grams on purge alone, which is often more than the actual part weight.
- Can I reduce purge waste?
- Yes, to a point. Lower your 'flush multiplier' in Bambu Studio (default is often 1.0x, tuned users go to 0.4x-0.6x). Use the 'Flushing volumes' matrix to set lighter purges for compatible colors (white to white flush less than white to black). Reduce the number of color changes in the print itself by grouping same-color features.
- Where do I find the color swap count?
- In Bambu Studio, slice the print, then click the 'Flush data' or 'Filament change' panel in the preview. It shows total swaps and exact grams flushed. Orca Slicer shows similar data.
- Is multi-color printing worth the waste?
- For small prints, usually not. A 30 gram part with 40 swaps uses 320 grams of purge, meaning multi-color costs 10x the base material. For larger prints, the purge percentage drops. Worth asking: could you paint the part instead of printing in color?
- Does this apply to non-Bambu multi-material systems?
- The math works for any multi-material setup (Prusa MMU, Mosaic Palette, etc.), but purge-per-swap values differ. MMU2/3 often purges 15-25g per swap. Palette uses transition lengths measured in mm of filament, not grams. Use the custom profile and enter your system's known purge weight.