PrusaSlicer Cut Tool: Uneven Holes & Tolerance Headaches

Navigating the PrusaSlicer Cut Tool: Understanding Uneven Holes with Tolerance

PrusaSlicer's cut tool is an absolute game-changer for 3D printing enthusiasts and professionals alike, making it incredibly easy to split larger models into manageable pieces that fit your printer's build volume. It's a fantastic feature that saves countless hours of fiddling with CAD software just to divide an object. However, what happens when this very tool, designed to simplify our lives, introduces an unexpected complication? We're talking about the frustrating issue of uneven holes appearing when you apply a tolerance using the PrusaSlicer cut tool. Imagine meticulously splitting a model, adding precise keyholes for perfect alignment during assembly, only to find that when you print them, the holes on either side of the cut don't line up perfectly. This isn't just a minor annoyance; it's a significant roadblock that can lead to misaligned parts, wasted filament, and a lot of head-scratching.

This specific PrusaSlicer bug, observed in version 2.9.4 and potentially other iterations, throws a wrench into the otherwise smooth workflow of preparing models for print. Users expect the cut tool to maintain the integrity of their design, especially when it comes to crucial features like alignment pins and holes. When you apply a tolerance – a tiny offset designed to ensure parts fit snugly without being too tight – you assume it will be applied uniformly across all related features. But in this scenario, the individual editing of hole tolerances seems to cause a peculiar slicing inconsistency where the holes on opposing cut faces are not mirrored precisely. This directly impacts 3D printing accuracy, turning what should be a straightforward assembly into a struggle, or worse, an impossible task. It’s disheartening to discover that a feature meant to enhance precision actually introduces an element of unpredictability. Let's dive deeper into this issue, understand why it happens, and explore how we can navigate around these unexpected tolerance issues to get back to flawless 3D prints.

The PrusaSlicer Cut Tool Explained: A Closer Look at its Functionality

To truly grasp the impact of the uneven holes problem, it's essential to first appreciate the power and purpose of the PrusaSlicer cut tool functionality. This incredible feature is one of the standout aspects of slicing software like PrusaSlicer, empowering users to tackle projects that would otherwise be impossible on smaller 3D printers. Its primary purpose is straightforward yet vital: to allow you to split a 3D model into two or more parts. This is indispensable when your object exceeds the dimensions of your printer's build plate or when you want to print different sections with varying print settings or colors. The process usually involves defining a cut plane, selecting the orientation, and then, crucially, deciding how these newly separated pieces will rejoin later.

This is where connectors come into play. PrusaSlicer offers the convenience of automatically adding various types of connectors, such as pins and holes, to help you perfectly align and reassemble the printed parts. The magic happens when you define a depth tolerance for these connectors. Tolerance in 3D printing is a small, intentional gap added between mating parts. For instance, if you have a 5mm pin and a 5mm hole, they might fit too tightly due to slight inaccuracies in the printing process. A 0.5mm tolerance on the hole would effectively make it 5.5mm, ensuring a comfortable, yet secure, fit. The expectation is that when you specify a tolerance for a hole, this offset is symmetrically applied to both halves of the cut, ensuring that the male and female components (or the corresponding holes on both sides of a split) are perfectly complementary. The typical PrusaSlicer workflow for using the cut tool involves selecting your model, clicking the cut tool icon, positioning the cut plane, optionally adding connectors like pins and holes, adjusting their size and depth tolerance, confirming the cut, and then often arranging the halves (e.g., cut side down) before slicing. This process should ideally be seamless, leading to two perfectly mating parts, which makes the observed slicing inconsistencies with uneven holes particularly perplexing and frustrating for users who rely on this precision for their 3D model preparation.

The Core Issue: Why PrusaSlicer's Cut Tool Creates Uneven Holes with Tolerance

Now let's zoom in on the heart of the matter: the PrusaSlicer bug that causes such frustration. Users have reported a perplexing phenomenon: when the PrusaSlicer cut tool is employed with a 0mm tolerance, the holes created on both sides of the cut align perfectly. This is exactly what we'd expect, ensuring a flawless fit for any alignment pins. However, the situation dramatically changes when a non-zero tolerance, such as 0.5mm tolerance, is applied, especially when individually editing the properties of these holes. Instead of a precise, symmetrical split that accounts for the tolerance, the cut becomes surprisingly uneven, leading to significant 3D print misalignment.

Imagine you have a complex print with several keyholes designed to perfectly interlock. When you use the cut tool, you carefully place these holes and then, wanting a slightly looser fit for easier assembly, you go into the settings for each hole and manually set its depth tolerance to, say, 0.5mm. Based on the PrusaSlicer functionality, one would logically assume that this tolerance would be applied symmetrically to both halves of the cut. The expectation is that if a hole starts at layer X on one half, its corresponding hole on the other half would also start at layer X, with the tolerance simply adjusting the hole's dimensions uniformly. But what's observed is a different story: after slicing, inspecting the layer view reveals that the