Prusa's INDX keeps purge waste near zero on color changes

INDX vs AMS purge waste starts at 83 grams. That is what Bambu Studio reports for one four-colour test cube. The cube takes 153 colour changes, and every change flushes plastic. On a Bondtech INDX, every material keeps its own nozzle, so the same print skips the flush and purges only about 13 milligrams per swap, around 2 grams in total.

What purging is and why single-nozzle systems cannot avoid it

A single hot end holds a few cubic millimetres of melted plastic at all times. When the slicer calls for a new colour, that old plastic is still in the melt zone. The printer has to push it out before the new colour prints clean.

Bambu Lab’s own documentation calls this step flushing, and it explains why the volume changes from pair to pair. Dark to light needs a big flush, because a trace of black shows up in white. Light to dark needs much less. The flushed plastic lands in a purge blob beside the plate. Some of it goes into a prime tower, which grows as tall as the highest layer with a colour change.

The flush volume depends on the nozzle and the colour pair, and the size of your part has no bearing on it. A 5 gram keychain in four colours pays the same per-swap toll as a 500 gram vase.

The Bondtech INDX upgrade for the Prusa CORE One has no flush step. Each of the eight materials loads into its own thin passive tool with its own filament path and nozzle. No two materials share a melt zone, so there is nothing to flush. Prusa says each change still purges about 13 mg to stabilise the pressure in the nozzle. A cheaper two-nozzle printer does the same for two materials, dropping the flush without paying for eight tools.

That is a vendor describing a rival architecture, so read it as a claim and look for measurements elsewhere.

How much filament does a purge tower waste?

A four-colour Bambu Cube sliced at 0.2 mm layers needs 153 filament changes and 83 grams of wasted filament. Raise the layer height to 0.28 mm and both drop together, to 111 changes and 61 grams.

Money uses Prusament PLA at €29.99 per kilo, which works out at three cents a gram. The 12 second tool change is Prusa’s own figure for the INDX. The 40 second swap is Prusa’s figure for filament swaps on printers that run out of dedicated nozzles, so it’s the softest number in the table.

A Bambu Cube is a 30 mm cube. Bambu’s wiki calls it an 11 gram object, and even printed solid it couldn’t weigh more than about 34 grams, so the purge outweighs the part at least twice over.

In a harsher case from Bambu Lab’s documentation, one roughly 35 gram model was printed standing upright rather than flat on its side. That single choice burned an extra 180 grams and eleven extra hours. Orientation alone moved five times the model’s weight into the bin.

INDX vs AMS purge waste measured in print hours

Filament costs little next to machine time, and the gap between the two architectures is wider in hours than in grams.

On every AMS-style swap the printer retracts the old filament, cuts it, then feeds the new one. It extrudes until the colour runs true, wipes, and travels to the prime tower and back. None of that lays down part geometry. Across 153 swaps it adds up to well over an hour on a print that might only be four hours of extrusion.

An INDX swap parks the current tool, moves, picks up the next one, heats it and resumes. Prusa quotes as little as 12 seconds for the whole sequence. The passive tools carry no heater and no wiring, which keeps them light enough to swap that fast.

Longer prints also fail more often, and the extra hours drive that risk far more than the extra grams do. A 30 hour multicolour print that fails at hour 26 loses much more than €2.49 of purge. For a hobbyist printing one showpiece a month, the difference is an evening. For a small workshop running a plate a day, it is roughly a working day recovered each month.

What could cancel the saving

Dedicated nozzles do not get the waste to zero. Prusa says every tool change purges about 13 mg, so the 153-swap cube still leaves about 2 grams behind. Parked tools cool quickly, which Prusa says stops them oozing. Both figures come from the vendor, and no independent measurement has been published yet.

Tool changes also cost time even when they cost no plastic. On a print with hundreds of very short colour swaps, the docking travel can cancel out the time the missing purge saves. Creality’s KliTek swaps only the nozzle instead, and each colour-change design is weak at something different.

Saving about 81 grams per cube is worth about €2.43. The eight-tool Prusa Edition conversion kit for the CORE One costs $999, or €899 including VAT, and the four-tool version costs $749 or €669. PrintNexus documents both alongside the staged Founders Edition rollout. On filament savings alone, that kit needs roughly 370 four-colour cubes before it breaks even. The kit only fits Prusa’s own machine, and the 2026 CORE One refresh held that printer’s price steady even after adding hardware.

Prusa showed a CORE One printing eight materials at once on the Formnext floor, so the architecture works in public. A trade-show demo says nothing about reliability over a thousand hours.

Buy the INDX because you want eight materials, faster swaps and fewer failed overnight prints. It mostly gives you back hours, and the filament saving is a small bonus.