What Causes the Unable to Slice Error in Cura? (How to Fix?)

While modern slicer software allow the configuration of many parameters to make the 3D printing experience smoother, the primary purpose of the software remains the same, which is to ensure that the 3D model you provide is printable by the 3D printer and convert it to a format that the 3D printer can understand.

On the other hand, as it would make no sense for the slicer software to allow the printing of a 3D model that it thinks is not possible to print, in such scenarios, the slicer usually displays an error message and halts the slicing process until the factor that prevents the 3D model from being printable does not exist anymore.

Today, we will be talking about the “unable to slice” error in Cura, in particular, which is an error that prevents the slicing process from moving forward and displays a message that pops up with a short description of what could potentially be causing the problem, but unfortunately, the brief description itself is not enough to find the actual cause more often than not.

So, what can actually cause Cura to display the “unable to slice” error, preventing the slicing process from operating as intended?

The primary culprit behind Cura displaying the “unable to slice” error is the 3D model not fitting the build space due to various problems, which makes up the majority of the cases behind this error.

On the other hand, while rarer due to it being a multi-extruder-specific case, attempting to slice the model while the extruder it’s assigned to is disabled is another issue that can cause the “unable to slice” error to occur.

Next up, we will analyze the factors that can cause the “unable to slice” error in Cura in more detail, look at ways to resolve the problem as quickly and effortlessly as possible, and finally, go through the process of completely resetting your Cura installation to defaults.

What Causes the Unable to Slice Error in Cura?

The “unable to slice” error in Cura is one of the last things any 3D printing enthusiast would want to see, as the process of slicing a model is often a smooth one without any hiccups involved, and the possibility of problems occurring comes into mind usually after the 3D printing process itself starts.

In most cases, you will encounter the “unable to slice” error in Cura if the 3D model you’re attempting to slice does not fit the build area, even though it may seem like everything is fitting perfectly on the screen when you take a look.

Below, we have listed some of the factors that can cause your model to technically not fit even though it looks like it does:

  • The 3D model touches the “disallowed areas” of the build area, which are depicted with a darker shade of gray. These areas are disallowed for safety purposes as they are incredibly close to the edges of the build plate.
  • Brims, skirts, and rafts are outside the build plate or in the disallowed areas. While the 3D model itself may look like it’s not touching the disallowed areas, the brim, skirt, or the raft you have added can be the culprit.

Another case that can trigger the “unable to slice” error in Cura, which only applies if you are using a multi-extruder setup, is the extruder you have activated for the model being disabled, which makes it impossible for Cura to perform the slicing process.

This case can occur if you import the 3D model first and allow the Cura to assign it an enabled extruder, and then disable the extruder afterward, as the assigned extruder won’t automatically change due to you disabling the extruder.

A handy trick is to keep an eye color of the model while you’re in the Prepare tab, which should be the same color as the color code of the filament you’re using in Cura. If Cura is unable to slice the model for any reason, it will show diagonal white and gray lines that are slightly faded before you even click the Slice button.

Finally, while rare, one last factor that can cause the “unable to slice” error is all of the models you have imported being selected as a modifier mesh or a support blocker, meaning that there won’t be anything for Cura to slice.

On the other hand, as this cannot happen unless you manually set the models as such since all models automatically import as regular meshes, it’s only something to keep in mind if you have performed such modifications.

How to Fix the Unable to Slice Error in Cura?

While Cura’s error messages may not always be too precise about what exactly is causing the problem, especially for those who don’t have a lot of experience with the slicer, it’s usually possible to resolve these errors without a lot of trouble once the solution path is clear.

Below, we have listed the potential solutions that we recommend applying to fix the “unable to slice” error in Cura:

  • Make the 3D model smaller. If any part of the 3D model is clipping the disallowed areas even though you cannot see it, making the model smaller can be helpful to make it practically impossible for the disallowed regions to come into contact with the 3D model.
  • Set the Build Plate Adhesion Type parameter to None. The Build Plate Adhesion Type parameter is the one that allows you to choose between a brim, raft, or skirt, and setting it to none will make it none of them will be printed.
  • Remove the disallowed areas. For this process, you will need to find the definition file that belongs to the printer you’re using in the Cura folder (such as Program Files/Cura/resources/definitions for Windows) and remove the values inside the “default_value” key under the “machine_disallowed” areas key. Make sure to make a backup of the file before you modify it.
  • Activate an extruder that is currently enabled. If you have a multi-extruder setup, you will see the extruder selection tab on the left pane, denoted with the numbers of the extruder. Disabled extruders should be deactivated, and at least one enabled extruder should be active.
  • Reset the Mesh Type of the model to normal. You can perform this process by clicking the Per Model Settings tab on the left pane while the model is selected and choosing the Normal Model option (leftmost).

How to Completely Reset the Cura Installation to Default?

In many cases where errors seem to be unsolvable, resetting the software to its defaults is a process that can come in very handy, as a piece of software that is configured to its default settings is unlikely to throw any errors.

The easiest way to reset your Cura installation to its default state is to click the Help button on the top menu, choose the Show Configuration Folder option from the dropdown, go one level up to the folder named “cura”, and delete all the files there, which will erase all configuration.

After successfully applying this process, the Cura should start as if you have installed it for the first time and take you through the onboarding flow.

Wrapping Up

Slicer software not fulfilling its duty of slicing your model and preparing it for the 3D printing process can definitely be both disappointing and irritating, but in most cases, unless a software malfunction is involved, there is a good reason for the slicer to not go through with the process.

To quickly recap, in almost all cases, the Cura “unable to slice” error will pop up because the 3D model you have imported does not fit the build area due to various less-apparent reasons than the model actually not fitting, such as itself, the brim, the skirt, or the raft, touching the disallowed areas.

Aside from the build area issues, attempting to slice the model with a disabled extruder in a multi-extruder setup or manually converting the model mesh to a modifier mesh or a support blocker in a single 3D model scenario can also be the culprit in some cases.

Happy printing!