Multi-Color 3D Printing Explained: How the AMS Works

Multi-color 3D printing on a Bambu AMS works by swapping filaments through a single hotend, not by printing with several nozzles at once. The AMS holds four spools, and every time the print needs a different color it parks the current filament, cuts it, pushes 84 mm³ of plastic out of the nozzle to flush the old color away, and loads the next one. That takes about a minute and a third, and a detailed model can need it 900 times. Understanding that one number is the whole subject: color is cheap, changing color is not.

How Multi-Color 3D Printing Works: What the AMS Is

AMS stands for Automatic Material System. It is a box that sits on top of the printer holding four spools, each in its own tray, with a motorized feeder that pushes one filament at a time down a shared tube into the extruder. There is one hotend and one nozzle. The machine is not printing four colors simultaneously; it is printing one color, stopping, and becoming a different single-color printer several hundred times over the course of a job. /docs/studio/multi-color covers how a colour project is sliced, priced and printed.

That architecture is why an AMS is affordable and why multi-color prints behave the way they do. Nothing about the toolhead changes when you add colors. What changes is how often the printer has to interrupt itself. Our farm runs Bambu Lab H2S and P2S machines with a four-tray AMS on each, which is the same hardware most people have at home, so the numbers below apply to your own printer just as much as to ours.

What Happens During One Filament Change

The purge is the part people underestimate. A hotend holds a small reservoir of molten plastic, and you cannot print clean yellow while red is still sitting in the melt zone. The only way to clear it is to push the old color out with the new one until what comes out is the right color. Bambu's own H2S profile in OrcaSlicer specifies this exactly: the flush volume matrix is 280 mm³ for any color-to-color pair, multiplied by a flush multiplier of 0.3, which is 84 mm³ of filament extruded and discarded every single change.

• 84 mm³ of filament, which at PLA's 1.26 g/cm³ density is 0.106 g thrown away per change.
• About 1.3 minutes of machine time to park, cut, load, purge, prime, and wipe.
• Zero change to the part itself. None of that plastic or time ends up in your object.

Modern slicers soften the material cost by flushing part of the purge somewhere useful, into the model's own infill or into support structures, so the waste tracks the size of the print rather than being a flat penalty per change. Nothing softens the time cost. The printer is not extruding your part while it does this, and on a plate with a lot of changes that is where the hours go.

Why Time, Not Plastic, Makes Multi-Color Expensive

Take a real example: a 60 mm tall model that weighs 40 g in a single color. At 0.2 mm layers that is 300 layers. If the colors are spread through the model, the sort of thing you get from a painted or textured design, the printer changes filament on essentially every layer, once per extra color. Two colors means 300 changes. Four colors means 900.

Read the four-color row carefully. The part is 40 g. The purge is 95 g. More plastic ends up in the bin than in the product, and those 900 changes add 19.5 hours to a print that would otherwise take about two. That is the shape of a multi-color job on any AMS machine: the plastic roughly triples and the hours go up by an order of magnitude, and neither of those is a markup anyone chose.

The Design Decision That Sets the Price

Change count is a function of geometry, not of color count. A model with four colors arranged as horizontal bands, a layered nameplate, a striped vase, a two-tone enclosure, changes filament only when the print crosses a band boundary. That is three changes for the whole job, not 900. The same four colors sprayed across the surface of a figurine changes on every layer. Same palette, same mesh volume, two completely different manufacturing jobs.

The other lever is splitting the object. Four separately printed single-color pieces that snap together cost zero changes and zero purge, and they let you use colors an AMS could never reach in one job, like a soft TPU grip against a rigid PLA body. Designers who print a lot of multi-color parts reach for this more often than for the paint tool, and it has the side benefit of letting every piece be oriented for its own loads.

How Multi-Color Works at X3D Studios

Every color price here comes from a real slice of the print in its colors, never from a volume guess, and there are two ways to send one. Upload the Bambu Studio or OrcaSlicer project .3mf as you saved it, with filaments assigned to parts or painted on, and we slice each plate in the project's own colors on our standard 0.2 mm profile, then price that slice: the grams at the plastic's color rate, which rises with each color, purge and changes included. Or slice the plate yourself and upload the .gcode.3mf, and we print it exactly as exported, billed from the weight and hours your slicer measured. A plain STL or GLB carries no filament assignments, so it prints in one color.

Slicing it yourself is still the route for anything a project cannot carry. Each project plate prints from one filament type, and only filaments assigned to parts and painted areas print in color, so a color change set at a layer height prints in one color from a project but exactly as banded from your own .gcode.3mf, where the tool changes are already written into the file. Preparing the file is walked through step by step in Bambu Studio Multi-Color Print Setup, Step by Step, and How to Export G-code From Bambu Studio (.gcode.3mf) covers the export dialog itself. /multicolor-3d-printing sets out every rule a project has to meet.

Every sliced plate passes G-code safety validation before it reaches a printer in Austin, Texas, and every job is monitored by the same system that took the order while it runs, so a 20-hour plate is being watched rather than hoped over.

Everything else about a multi-color order is ordinary: $1.00 minimum per part, billable weight rounded up to the whole gram, $7 standard US shipping and free on cart orders of $49.50 or more, and a 340 x 320 x 340 mm build volume on the H2S. Full rates for every material are on /pricing, and the same layer-height and infill choices apply, which 3D Printing Layer Height Explained: 0.08 vs 0.2 vs 0.28 and 3D Printing Infill Explained: Patterns, Density, and Cost cover in detail.

FAQ

How does a Bambu AMS print more than one color?

It feeds up to four, one per tray, on a single AMS unit. The printer still has one nozzle, so those four colors are printed one at a time with a filament change between them. More than four in a single job needs a second AMS chained on, and that is how our farm prints up to eight, with a $25 fee once per order line for loading the second unit.

Why does multi-color 3D printing waste so much filament?

Because the hotend has to be flushed clean between colors. Bambu's H2S profile purges 84 mm³ per change, about 0.106 g of PLA. That sounds trivial until you count the changes: a 300-layer four-color print does roughly 900 of them and purges about 95 g, which on a 40 g part is more waste than product. Slicers reduce the sting by flushing some of it into infill and supports.

Does multi-color printing cost more per gram?

Yes, a little. PLA is $0.12 per gram all-in in one color, $0.15 in two, $0.17 in three and $0.19 in four: +$0.03 at two colors and +$0.02 for each color after. On a sliced plate you upload, the rest of the extra cost comes from two real quantities the file already contains: the purged filament is billable weight like any other gram, at the same color rate, and the hours the weight cannot explain bill as machine time at $1.50 per hour. A four-color plate is expensive because it genuinely occupies a printer for most of a day.

How do I make a multi-color print cheaper?

Move the color boundaries. Bands by height need three changes instead of 900. Confine painted detail to a short stretch of layers rather than the whole model. Split the object into single-color pieces that assemble. And if the cheap layout is a color change at a set height, slice the plate yourself and upload the .gcode.3mf at /print: a project prints only part and paint assignments in color, while your own sliced plate prints exactly as exported, and the quote is the numbers your slicer measured.