Bambu Lab AMS Explained: Multi-Colour Printing and What It Costs in Filament

The AMS — Automatic Material System — is the feature that made Bambu Lab famous for effortless multi-colour printing. It is genuinely impressive: load up to four spools, and the printer switches between them automatically mid-print. But multi-colour printing has a real cost in wasted filament that many buyers do not understand until they see their first purge tower. This guide explains how the AMS works, what it costs to run, and how to minimise the waste.

How the AMS Works

The AMS holds up to four filament spools and feeds them to the printer on demand. When a print calls for a colour change, the system retracts the current filament, loads the next, and resumes. There are two versions in the current range:

• AMS Lite: Used with the open-frame A1 and A2L. Four spools sit on an external rack and feed into the single nozzle. Up to 4 colours.
• AMS 2 Pro: Used with the enclosed and active-chamber machines (P2S, X2D, H2S, H2D). An enclosed unit that also actively dries filament, and can be daisy-chained for many more colours.

For larger colour counts, multiple AMS units can be linked — Bambu machines support up to 16 colours (and some configurations more) by chaining units together.

The Hidden Cost: Purge Waste

Here is what every multi-colour buyer needs to understand. Because a single nozzle handles all the colours, every colour change requires purging the old colour out of the nozzle before the new one prints clean. That purged filament has to go somewhere — usually into a 'purge tower' printed alongside your model, or flushed as waste.

On a complex multi-colour print, this purge waste can consume 15–25% of your total filament and print time. A model that uses 30g of visible filament might consume an extra 40–60g in purging across many colour changes. This is not a flaw in the AMS specifically — it is inherent to single-nozzle multi-colour printing across the whole industry — but it is a real running cost that affects the economics of multi-colour work.

How to Reduce Purge Waste

• Minimise colour changes per layer. Designs where colours are grouped by height (one colour finishes before the next begins) purge far less than designs that alternate colours every layer.
• Use 'flush into object infill' and 'flush into support' options in Bambu Studio, which redirect some purged material into parts of the print that are hidden, rather than wasting it entirely.
• Tune flushing volumes. Bambu Studio lets you adjust how much is purged between specific colour pairs. Light-to-dark transitions need more purging than dark-to-light; tuning these saves material.
• Consider a dual-nozzle machine for support-heavy work. The X2D and H2D dedicate a second nozzle to support material, eliminating purge waste between part and support entirely.

The AMS Also Dries Your Filament

The AMS 2 Pro does more than switch colours — it actively dries filament, which is a significant benefit independent of multi-colour printing. Hygroscopic filaments like PETG, TPU, PA (Nylon), and PC absorb moisture from the air and print poorly when wet, causing stringing, bubbling, and weak layers. The AMS 2 Pro's active venting and drying keeps filament dry during storage and printing — Bambu states it dries up to 30% faster than sealed heating. For anyone printing engineering materials, this is a real reliability advantage.

Which Filament Works Best in the AMS

The AMS handles standard filaments — PLA, PETG, ABS, ASA, TPU — reliably. A few practical notes:

• PLA and PETG are the easiest and most reliable in the AMS, ideal for multi-colour work.
• TPU (flexible) can be challenging in the AMS Lite due to its flexibility in the feed path; firmer TPU variants (higher Shore rating) feed more reliably.
• Cardboard-spool filament wound cleanly and consistently feeds best — tangles and uneven winding cause AMS feed errors. This is one reason consistent spool quality matters for multi-colour printing.

Eolas Prints manufactures PLA, PETG, TPU, ABS, and ASA filament in Spain wound for consistent feeding, certified to ISO and REACH standards — all compatible with the Bambu AMS.

Is Multi-Colour Worth It?

For decorative prints, signage, models, and gifts, multi-colour printing adds real value and the purge cost is acceptable. For functional engineering parts, multi-colour is rarely needed — and where multiple materials are required (rigid plus flexible, or dissolvable supports), a dual-nozzle machine like the X2D or H2D is more efficient than AMS purging. Match the approach to the work.

Available from Eolas Prints

Eolas Prints is an authorised Bambu Lab reseller based in Cantabria, Spain. We stock Bambu printers, AMS units, and manufacture our own filament range — all shipping across Europe. Contact us for advice on building a multi-colour or multi-material workflow.