Multicolor purge simulator by batch size

What the simulator computes, and what it leaves to you

The simulator asks for four values you type in by hand. The mass of one part, the purge for a print containing only that part, the number of parts you want, and the purge for a batch containing all of them sliced in one job. Quantity has to be a positive whole number. There is no field for supports or for purge redirected into objects: the tool assumes one part mass, shared by both scenarios. Count each gram once, redirected purge included, and if support mass changes between the single part and the batch, compare the complete slicer totals outside the tool instead.

From there, two simple formulas apply. Separate scenario: (part mass + single-print purge) × quantity. Batch scenario: part mass × quantity + batch purge. The tool then shows the difference, separate minus batch, and the batch mass per part, meaning batch divided by quantity.

What the tool does not do matters just as much. It applies no universal purge rate and does not guess batch purge from single-part purge. The Prusa Knowledge Base shows that purge depends on the filament pair and the direction of the change. Slicing each scenario for real stays mandatory. If you are still deciding how to approach multicolor at all, the guide to multicolor 3D printers covers the options without pretending to know your purge numbers.

Where to read the masses in your slicer

In PrusaSlicer, the Prusa Knowledge Base article on the MMU describes two modes for purging volumes. The first uses configuration values: a purging volume in the printer settings, adjusted by a purge volume multiplier at the filament level. The second uses a project-specific matrix, where each cell holds the volume needed to switch from one filament to another. The article does not describe how post-slicing statistics split material between parts and tower: read those figures in your own slicer version and note the convention you used.

In OrcaSlicer, the wiki documents a command-line statistics export. For each plate it writes a JSON file with print time, filament and feature totals, and the same detail per layer and per object. The wiki notes these are the same files produced by the Export Statistics preference in the GUI. It does not say how the prime tower is counted in them: check that in the file before relying on it to separate part mass from purge mass.

The OrcaSlicer wiki also lists a clone-objects option on the command line, which sets a copy count for each loaded object. It lets you build the batch scenario without duplicating files by hand. Both slicers have their own pages here: OrcaSlicer and PrusaSlicer.

A worked example with made-up numbers

The figures below are invented to show the mechanics. They come from no slicer and apply to no real filament. Suppose a two-color part weighs 25 g. Sliced alone, the slicer reports 8 g of purge. You want 6 parts. Sliced as a batch of 6 on the same plate, the slicer reports 20 g of total purge.

Separate scenario: (25 + 8) × 6 = 198 g of filament. Batch scenario: 25 × 6 + 20 = 170 g. Difference: 198 minus 170, or 28 g less material for the batch. Batch mass per part: 170 divided by 6, roughly 28.3 g, compared with 33 g per part when printed separately.

The sign of the difference is not guaranteed. If your slicer purges at every color change on every layer across the full height of the batch, batch purge can climb faster than you expect. If instead it groups changes and flushes into the infill of neighboring parts, it can drop sharply. Only slicing the actual batch tells you which way it goes. Re-enter the numbers for each candidate quantity rather than extrapolating from one batch.

Why not all purge is waste

The OrcaSlicer wiki, in its revision of 14 October 2026, documents three flush options. The first flushes into the objects' infill, which may lower waste and print time, with one caveat: if the walls are printed in transparent filament, the mixed-color infill shows through. The second flushes into a designated object, whose walls and infill are printed with the new filament, so its colors end up mixed. The third flushes into the objects' supports.

The wiki states that none of these take effect unless the prime tower is enabled. It adds that with a Type 2 wipe tower, purging into objects is only used on single-extruder multi-material printers with purge in prime tower enabled. In other words, a checkbox you can see does not always translate into an effect on your machine.

For the simulator, this changes how you read the numbers. Purge can be redirected into infill or supports instead of being discarded. Check how your slicer accounts for it and count each gram once, either in part mass or purge, never both. Keep the same convention and shared per-part mass in both scenarios; if that assumption does not hold, compare complete totals outside the simulator.

Traps that skew the comparison

The first trap is reusing a purge value measured on one color pair for another. The Prusa Knowledge Base gives an example: with unload values of 80 for black and 20 for white, and load values of 30 for black and 70 for white, the black-to-white transition needs 150 mm³ while white-to-black needs only 50. Prusa attributes the gap to heavier color contamination going from dark to light. These are example values, not recommended settings.

The second trap involves special filaments. According to Prusa, soluble support filament and filaments with additives, such as highly glossy or glitter materials, most likely need increased purging volumes compared to the standard example. If your batch mixes in that kind of material, slicing the batch is the only valid reference.

The third trap comes from versions and profiles. Statistics exported by OrcaSlicer are tied to the version and profile in use. Change either between your two slicing runs and the comparison falls apart. The wiki even lists an option to allow slicing a 3MF saved by a newer OrcaSlicer version, off by default, which shows how much versions matter.

Reading the result and moving on to cost

A positive difference means the batch consumes less total material than separate prints. The batch mass per part lets you compare several quantities against each other. If it stops falling as you add parts, grouping no longer helps on the material side. A negative difference is not an error. It tells you that with your settings, the batch purges more than the sum of single parts, for example when every layer of the batch triggers a change.

The simulator works in filament mass, not money or time. To turn mass into cost, carry the total of your chosen scenario into the print cost calculator, which adds the price side. Machine time cannot be derived from mass. Read it from the slicer for each scenario.

Keep your exports as a record. A batch that looked favorable can stop being favorable after a profile update, and you will want the earlier numbers to see what changed. If you are also budgeting for a multicolor unit or an add-on such as the Bambu AMS 2 Pro, the startup budget tool handles that side separately from per-print material.

Sources and limits

• Purging volumes (MMU) | Prusa Knowledge Base Prusa Prusa Prusa
• multimaterial_settings_flush_options · OrcaSlicer/OrcaSlicer Wiki · GitHub
• cli_misc · OrcaSlicer/OrcaSlicer Wiki · GitHub

We organize manufacturer and community documentation; we have not measured these products ourselves. The manual for your exact model takes precedence over general guidance.