Negative volume | Prusa Knowledge Base

The negative volume lets you subtract one mesh from another.

That way you can, for example, create easily resizable holes directly in PrusaSlicer.

Right-click on a model and pick Negative volume from the context menu. Then select the negative volume shape. You can either pick one of the basic shapes (cube, cylinder, sphere), pick one from the Shapes Gallery or use Load... to import a custom mesh.

The subtraction of the negative volume happens during slicing, the actual model geometry is not modified. That means it is not possible to export an STL with the subtracted negative volumes.

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15 comments

Catra

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"That means it is not possible to export an STL with the subtracted negative volumes." this no longer seems to be true, i have used this to get STLs with the negative space and volume gone, for example hollowing out a cylinder using a smaller negative cylinder.

StebiChikito

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How do you achieve this? I have been trying but get an error message. Unable to perform boolean operation on model meshes.

srmalloy

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It's inconsistent. I had an SVG logo I wanted to incise into the top of a box object, and I added the SVG, adjusted its thickness, then defined it as a cut, and I was able to save the box lid and cutout as an STL, but the lines on the logo were too thin, so I edited the SVG to thicken them, and went through exactly the same process, but this time I got the 'unable to save negative volumes' error. Trying several different ways to add the incised logo kept coming back to the same error, so I finally gave up and saved the whole thing as a 3MF file, which _does_ preserve the negative volume.

Philippe Racine

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Hi there! Is there a way to set "Priority over negative volume". As, I want a merged object to not be affected by the negative volume.

Thanks!

Meteor magnet

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I think> educational mold: for demo / feature. Cube with part lines. Substract to be molded item. pour whatever into subtracted space. new part or sculpture. I like the pick. but its a cool feature that should be expressed more creatively. Anyway Rock on!

Toby

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If my original model is too large for the print plate and I want to cut a bit off with a modifier, how can I achieve that? I added a negative volume but the slice button is greyed out (presumably, because my model is too large). But in order to apply the negative volume, I need to slice the model.

Toby

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I managed with the cut tool, but with the cut tool, it is difficult to get exact positions of the cut (which would of course not matter when cutting an object for attaching together again afterwards). So my question still stands: How to make an exact subtraction with the volume modifier,when the initial object is too bog for the platter?

Jan Kratochvíl

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Hello. Cutting model with modifier is unfortunately not possible right now.

Emili Paniello

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Reduce la escala primero, Cortalo y devuelvelo a la escala que estaba inicialmente 100%

ROARSOMEDADO

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I am curious, would it not simply be possible to add a shape to the model, give it 1 paremeter, no infill, no top or bottom layers, (assuming that is what you are seeking) and then place it where you want the negative space to be? This is a late entry to this convo, but thought I would add because of what I am trying to do.

Jan Kratochvíl

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Hello. I've tried it and the shape is not substracting itself from model, so there is no change. But interesting thinking :-)