Multicolor printing costs: hardware, purge and project time

Three items to record in a multicolor budget

Start with the initial investment: filament-changing unit, spools and possibly a printer. Then record purge material. Prusa explains that incoming filament pushes out melted plastic left in the nozzle during a transition. Depending on the documented settings, that material may go into the tower, infill or a wipe object. It is therefore not necessarily all discarded outside the parts.

Also record estimated duration and how you value machine occupancy. The cited pages do not establish your monetary cost or electricity use. Add your own prices and rates in the appropriate calculation and record the assumptions. A volume in cubic millimeters, a mass in grams, time and money are separate quantities.

Keep a financial total alongside the item breakdown. The multicolor buying guide covers hardware; slicing supplies project estimates here. Count each relevant amount once: part, supports and external purge, then any failed prints separately. Purge already included in infill must not be added again to the reported total mass.

How PrusaSlicer puts a number on purge volume

The Prusa documentation describes two ways to set purge volume in PrusaSlicer. The first uses values from the configuration: a Purging Volume in Printer Settings under Single extruder MM setup, which you can tune per filament with a Purge Volume Multiplier under Filament Settings, Advanced. In this mode the purging matrix cannot be edited.

The second way uses custom project-specific settings. Opening the purging volumes window shows a matrix in which each cell is the amount of filament to purge when changing from filament X, in the left column, to filament Y, in the top row. In this mode the configuration values are not used. This is the mode that makes a costing case repeatable, because every transition has an explicit value you can write down.

Prusa's example values show why the cost is asymmetric: black is listed with an unload of 80 and a load of 30, white with an unload of 20 and a load of 70. Black to white therefore totals 80 plus 70, or 150 mm³, while white to black totals 20 plus 30, or 50 mm³. Prusa notes that soluble support filament, or filaments with additives such as high gloss or glitter, will most likely need larger volumes than these examples. These are illustrative PrusaSlicer values, not measurements of another system and not a universal default in grams.

The wipe tower: one tower, sized by color changes

The PrusaSlicer wipe-tower page says one smart tower is printed regardless of the number of objects in a job and that its size depends on the number of color changes, not object size. It says multiple copies or large objects can improve overall filament-use efficiency. This is documented behavior of that feature, not a measurement of total savings, time or cost for every batch.

If several copies share color changes on the same layers, test whether the tower is pooled in your slice; the Prusa page describes one tower for a job. It gives no universal waste rate or time saving. Profile, model and color assignment affect the result, so use the batch-size purge simulator to explore inputs and then verify them with your own slice.

Prusa also points out that the tower is rarely solid: the ratio of sparse to dense infill is adjusted automatically every layer based on the current number of color changes. The real tower size only shows in the G-code preview after slicing; the 3D view shows its maximum footprint.

Settings that cut purge, and what they cost you back

The Prusa documentation describes three levers. The first, marked experimental, skips the sparse layers of the tower, meaning layers without a tool change. Prusa says this saves material and in almost all cases reduces print time, and quantifies the effect on its own set of multi-material projects: total print time reduced by 3.16% and filament deposited on the tower reduced by 16.17%. Those are results on Prusa's project set, not a market average, and the option comes with machine-specific recommendations you should read in the documentation before enabling it.

Wiping into infill can reduce tower material, but the documentation says that option alone cannot always eliminate the tower because some models lack enough infill. A wipe object can also receive some residual filament, but its colors will mix and slight artifacts may appear. Do not assume the object absorbs all purge; inspect the sliced G-code.

A wipe object can be a secondary part whose surface color does not matter for your use; Prusa gives a mechanical part as an example. Filament colors mix in it, and the manufacturer notes slight artifacts may appear during changes. Do not count its mass as an equivalent production part without checking the result.

A repeatable slicing test, step by step

To cost a project, first lock down what must not move: the same file, the same printer and filament profile, the same layer height, the same supports. If you use the project mode of the purge matrix, write down every transition value. Then slice the part once in a single color and once in multicolor, and record the filament mass and time the slicer reports for each. The difference describes the predicted mass and duration gap between these scenarios; it does not by itself give a complete cost or physical result.

For a batch comparison, slice the copies with the same file, profile, settings and colors, then record total mass and duration. Dividing those totals by the number of copies gives an average allocation per part, not the actual runtime of an isolated print or a monetary cost. Check that the copy layout matches your use; add filament price and time value separately in the print cost calculator.

Finally, date your assumptions. A purge matrix, a price per kilo and a slicer version all drift over time. A cost noted with its date and version can be compared later; one without a date will contradict itself six months on and nobody will know why.

Hardware: incremental cost versus a full purchase

Hardware scope depends on your starting point. If you own a printer, check module compatibility and every additional item its manufacturer requires; the unit alone is not necessarily the complete shopping list. If starting from zero, compare complete configurations in your market using verified offers or quotes. Keep initial spending separate from later maintenance and consumable replacement.

We do not list prices on this page; they shift by retailer and season. Use the startup budget tool to set your own envelope, then add the recurring buckets you calculated in the previous section. A unit such as the Prusa MMU3 is evaluated this way: a one-time purchase, then purge and time on every project according to the settings described in the PrusaSlicer documentation.

Batch filament efficiency may reduce purge volume allocated per copy when the tower is shared, but that alone does not establish hardware payback. Payback depends on actual purchase price, project mix, other expenses and the value you assign to time. Compare your own scenarios rather than assuming a large batch makes the purchase worthwhile.

What this method does not tell you

The purge examples and options here come from the cited PrusaSlicer pages; the wipe-tower article is categorized under “PrusaSlicer 2.9 (Legacy).” Behavior and interface labels can differ by version. These pages document PrusaSlicer/MMU workflows, not other filament-changing systems or a specific printer model. Check the documentation for your version and system before transferring settings.

Tower purge is not the whole loss on a project: supports, skirts, failed prints and calibration tests add up on top, with other causes. Treating them as one number muddies the diagnosis. Likewise, opportunity cost of time is an assumption you set, not a loss the slicer measures.

Prusa’s experimental-option results are from its own project set. Batch efficiency depends on the number and sequence of changes, model, colors, materials and settings. Slicing your file gives estimated mass and duration for that profile; it does not measure electricity use, the value of time or a physical result.

Sources and limits

• Purging volumes (MMU) | Prusa
• Wipe tower | Prusa

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