The Hidden Cost of Your AMS: Multicolor Purge Waste, in Real Money

If you print multicolor with an AMS, an MMU or a CFS and you sell your prints, there's a cost line you're almost certainly not putting in your quotes: the filament your system throws away on every color change. It's not small. In some cases it's more than the part itself.

In this article I turn the community's measured numbers — purge grams, swap times, sacrificial towers — into money, and show you how to price it in before it eats your margin.

Why the AMS wastes: purging

A single-extruder system (Bambu Lab AMS, Prusa MMU, Creality CFS, Anycubic ACE) pushes every color through one nozzle. At each change it must flush the previous color until the new one runs clean: that material ends up in the purge tower or in the infamous "poop" pile behind the printer.

How much goes depends mostly on the direction of the change:

• light to dark: 50-100 mm³ (cheap — dark covers everything)
• dark to light: 150-300 mm³ (expensive — a shadow of black ruins white)

Multiply by the swaps in a real print. A well-known benchmark — the Bambu Cube at 0.2 mm layers — makes 153 color changes: 83 grams of waste. And Bambu Studio's default flushing volumes are generous: users on the official forum measured that after calibration you need less than half of what the slicer purges out of the box.

Measured numbers: AMS vs dedicated toolheads

The most-cited comparison is CNC Kitchen's (Bambu X1C + AMS vs the toolchanging Prusa XL, same model): the toolchanger saved 26.5 grams of filament and 50 minutes on a single 9-hour print. On the 3-color figurine plate Tom's Hardware used to test the Snapmaker U1 (90 color swaps), the gap is even more brutal:

Time follows the same curve: a color change on an AMS costs 1-3 minutes of unload, load and purge; a toolhead swap costs 10-15 seconds. On the same multicolor print: +24 minutes for the U1, +2.5 hours for a P1S with AMS.

The math in money (what belongs in the quote)

Take a realistic multicolor print: a 200 g model, 4 colors, about a hundred swaps.

• Purged material: ~50 g × €25/kg = €1.25
• Extra machine time: ~2 h of swaps/purging × €0.60/h (depreciation + power on an X1C) = €1.20
• Extra wear on the extruder and cutter: hard to pin down, but not zero

Total: ~€2.50 of hidden cost on a single print. Sounds small? At 20 multicolor prints a month it's €50/month, €600/year — straight into the purge tower. And if you priced that 200 g part on the "visible" material only, those €2.50 come out of your margin, not your customer's pocket.

Cut the waste first (then price what's left)

1. Calibrate your flushing volumes: Bambu Studio defaults can be double what you need. Half an hour of calibration = 40-50% less purge, forever.
2. Raise the layer height if the model allows it: fewer layers = fewer swaps. On the Bambu Cube, going from 0.2 to 0.28 mm cuts waste by 26%.
3. Purge into infill and supports: the slicer can hide transition material inside the part.
4. Order colors light-to-dark where possible: dark-to-light changes cost 3-4× more.
5. Batch multicolor objects on the same plate: swaps amortize across parts.

Price it in (30 seconds)

In the Stimalo calculator multicolor waste needs no spreadsheet: enter the total weight consumed (model + purge, straight from your slicer) instead of the part weight alone, and the real time including swaps. Depreciation, energy and margin update by themselves — and the client PDF stays clean, with no "poop" line to explain.

If you print multicolor for money, the calculator is free and so is the full workshop manager: quotes, orders, filament inventory with automatic stock deduction. Your AMS will keep pooping — but you'll know exactly what it costs you.

What about toolchangers? 2026 is their year

Bondtech INDX, the Snapmaker U1 (the most-funded 3D printer in Kickstarter history), Sovol's M1D, the Flashforge Creator 5, a cheaper Prusa XL: multi-toolhead printing is reaching the consumer shelf precisely to kill the purge. When is switching worth it? It depends on how many multicolor prints you run per month — and yes, the break-even can be calculated. That's the next article.

Frequently asked questions

How much filament does an AMS waste per color change? Between 3 and 8 grams per swap with calibrated settings; up to 15 g with default flushing. In a typical 4-color print, 15-30% of total filament ends up in the purge tower.

How do you calculate the cost of a multicolor print? Total consumed weight (model + purge) × price per kg, plus real machine time including swaps (1-3 minutes each on an AMS) × your hourly machine cost. A calculator like Stimalo itemizes it for you.

Do toolchangers really eliminate waste? Almost: a small priming tower remains (4-15 g per print vs 40-100+ g), because each nozzle keeps its own color and nothing needs flushing.