Look at almost any multi-color 3D print next to the model on the plate, and you’ll spot a second object nobody asked for: a tall, ugly column of mixed plastic sitting off to the side. That’s the prime tower, and despite looking like scrap, it’s doing real work. Skip it and the first few millimeters after every color change tend to come out streaked, faded, or missing material entirely.
What it’s actually for
When a printer switches filament, whether that’s an AMS swapping spools, an MMU pushing a new color through the same hotend, or a multi-extruder machine parking one nozzle and picking up another, there’s leftover material from the old filament sitting in the nozzle and the melt zone. Some of that residue is the wrong color, some of it may be a different material entirely, and some of it has been sitting at temperature longer than it should, degrading slightly. If the printer went straight from that swap onto the model, you’d see the tail end of the old color, or unstable extrusion while the new filament works its way fully into the melt zone.
The prime tower gives the nozzle somewhere else to put that first bit of ugly extrusion. It also does a second job that’s easy to miss: stabilizing pressure inside the nozzle after a travel move or a purge, so the first lines printed on the actual model come out consistent rather than starved or blobbed.
Same feature, different names
This is one of those cases where slicers can’t agree on what to call the exact same structure. Bambu Studio calls it the prime tower, plain and simple, and it’s enabled by default, though it only actually gets generated on the plate for multi-color jobs, or when smooth-mode timelapse is turned on (more on that below). Cura also calls it the prime tower.
PrusaSlicer calls the same structure a wipe tower, and you’ll find its settings under Print Settings > Multiple Extruders > Wipe Tower.
OrcaSlicer, confusingly, uses both names for different halves of the same feature. The material-side settings, whether to use a prime tower at all and how much volume gets purged per color change, live under Print Settings and are labeled Prime Tower. The physical settings that control the tower’s footprint on the bed live under Printer Settings and are labeled Wipe Tower. If you’re hunting for a setting and can’t find it where you expect, check the other panel before assuming your slicer doesn’t have it.
If you’re still choosing between slicers for a multi-material setup, this naming quirk is a small part of a bigger set of tradeoffs; see our comparison of Cura, PrusaSlicer, and OrcaSlicer for the fuller picture.
Why it shows up even on single-color prints sometimes
A prime tower isn’t only for color changes. Bambu Studio will also generate one for a single-color print if you’ve turned on smooth-mode timelapse. That feature moves the toolhead to an out-of-the-way spot and wipes the nozzle before each snapshot, since melted filament can ooze out while the print head sits still for the photo. If the print is already multi-color, the timelapse function just reuses the tower that’s already being built for color changes rather than adding a second one.
The settings that actually matter
Width sets how wide the tower is, and it stays constant through every layer. Wider towers give more room per pass but eat more of the plate.
Prime volume is the amount of material purged onto the tower for each filament switch, and it’s a different number from flushing volume, which is the material purged elsewhere, into a waste chute or into the model itself, during the actual filament change sequence. It’s easy to conflate the two since they’re both “wasted” plastic serving a similar purpose, but they happen at different points in the process and are configured separately.
Brim adds a wider base around the bottom of the tower, purely to keep something that tall and thin from tipping over or peeling up mid-print. A prime tower that detaches partway through a long multi-color job can drag through the model or jam the nozzle, so this isn’t a setting to skip on tall prints.
The tower’s footprint isn’t fixed depth-wise; it’s calculated from how much material needs to be purged on a given layer. More color changes on a layer, or a higher prime volume, means a deeper tower footprint for that layer, down to a minimum depth so it doesn’t get too thin to stay standing, and the slicer smooths out the differences between layers so the tower doesn’t step in and out unpredictably as it grows.
Height works differently than you might expect. The tower doesn’t necessarily grow all the way to the top of the print. It only needs to reach as high as the last layer where a color change happens. If your model switches colors only in its lower half and finishes in a single color, the tower stops there too, since there’s nothing left to purge for.
Cutting down the waste
A tall prime tower on a long multi-color print can use a genuinely frustrating amount of filament, sometimes more than the visible model. Some slicers let you redirect part of that purge into the model itself, into infill or other solid areas the final part doesn’t show, instead of dumping all of it onto the external tower. It won’t eliminate the tower, but it reduces both the plastic wasted and the tower’s footprint.
Printers built around a true tool-changer, with a separate nozzle dedicated to each material, need far less of this kind of purging between colors, since the materials never actually share a hotend. That’s a different architecture from an AMS or MMU system, where every color runs through the same physical nozzle and has to flush out before the next one goes in.
Placement, if your slicer lets you choose
On Bambu’s X1-series printers specifically, avoid placing the prime tower near the excess-material chute, which sits at the left rear of the plate. That corner doubles as a camera zone for the printer’s built-in defect detection, and a tower sitting there can interfere with it. Bambu’s own guidance is to place the tower toward the right rear of the plate instead. On other printers this isn’t documented as a concern, but it’s worth checking your own machine’s documentation if defect detection or a similar camera feature is something you rely on.
If you’re staring at a big, blobby column next to your print and wondering whether it’s worth the plastic, the honest answer is: for anything with more than one color, yes, unless you enjoy troubleshooting why the first layer after every swap looks wrong.