Ultimaker Cura Arachne engine beta version

Ultimaker Cura Arachne version features an overhaul of the slicing engine used to create G-Code. The engine is enhanced with the in house developed Arachne code library.

Download Ultimaker Cura Arachne engine beta

Ultimaker Cura Arachne engine is currently in a public beta.


Download Ultimaker Cura Arachne engine

Released March 2021



The new Arachne Cura Engine introduces a new way of approaching the generation of thin wall and thin features of a model. For thin features a constant line width can be problematic.

For example, suppose you have a 1mm nozzle, but your geometry is a long thin piece of approximately 4.4mm wide. If you just start filling that thin piece using 1mm lines from the outside inward you will end up with a 0.4mm gap in the middle, while it's very hard to print a 0.4mm line with a 1mm nozzle. What if we could adjust the width of all lines to prevent the gap in the first place? We could just make 4 wall lines of 1.1mm. That way we have 4 lines which are very close to a 'normal' wall line, instead of 1 which is very far from normal.

This is why we introduce Arachne. The new library will provide a set of features to control the distribution of widths over the wall lines. You can choose whether the 0.4mm discrepancy should be dealt with using one line in the middle or several lines around the middle, or all lines over the width of the thin feature. As a user, 6 new print settings will be added to the print settings menu. These are:

  1. Variable Line Width Strategy
  2. Minimum variable line width
  3. Wall transition length
  4. Wall transition angle
  5. Wall transition distance filter
  6. Maximum extrusion area deviation

Tip: Read more about these new settings, along with the full release notes and a list of known issues on GitHub.


We encourage you to send your feedback on the new Ultimaker Cura engine. Your feedback can be received in a number of ways:


Please note that any Ultimaker Cura beta version is not suitable for everyday use. It should be only used for testing. In addition, this version represents a huge code change, so some features – like fuzzy walls – are not yet supported. There is also a higher chance that you run into a bug (some known, some unknown). These might reduce print quality.

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