Understanding modifier meshes

Smart Slice uses modifier meshes to locally adjust print settings.

What is a modifier mesh?

Modifier meshes are an advanced feature in Cura that facilitate region specific print settings. In a standard Cura workflow, a part is opened and placed on the build plate and the print settings are specified. These print settings apply to the entire model. For instance, the infill density that is specified is the infill density used for the entire part. In a modifier mesh workflow, users place additional STL geometries on the build plate and specify different print settings in the regions where these “modifier meshes” overlap the part geometry.

An example is helpful for understanding modifier meshes. In the image below, there are 2 parts on the build plate: a dogbone shaped part (solid yellow) and a cuboid (transparent yellow). The cuboid is considered the modifier mesh. In the image, the Print Settings are shown and so are the Per Model Settings. The Per Model Settings override the Print Settings but only in the region where the modifier mesh overlaps the dogbone.

Cura modifier mesh 1.png

A sliced view of this setup is shown below and it clearly illustrates the effect of the modifier mesh. In the overlap region, the Per Model Settings override the Print Settings. In this example, the infill density is 80% and 2 walls have been added in the overlap region. Outside of the overlap regions, the standard Print Settings apply.

Cura modifier mesh 1Cura modifier mesh 2

Modifier mesh usage in Smart Slice

Modifier meshes can be used in both the Validate and Optimize operations. Users can add modifier meshes to the build plate and these modifier meshes will be taken into consideration when the user executes a Validation. For Optimize, Smart Slice will start with the base geometry and add modifier meshes automatically. In some cases, the optimal solution does not require a modifier mesh so they are not always created during an Optimization. If modifier meshes are present when initiating an Optimization, a warning is issued and the user will be given the option to proceed, and if they agree, existing modifier meshes will be removed at the start of the Optimization.

Modifier meshes are important because they can be used to add stiffness and strength only in regions where it is beneficial to the part performance. Rather than, say, increasing the infill density and wall count for the entire part to meet the performance requirements, Smart Slice uses modifier meshes to add material only where it is needed. This save print time and material usage.

Known limitations

  • Specifying the thickness of Top/Bottom Layers for modifier meshes has no effect on the computed factor of safety and max. deflection. Therefore, the thickness of the Top/Bottom Layers should be specified using the Wall Line Count, Top Layers, and Bottom Layers settings as shown below (red arrows = ignored, green arrows = acknowledged).
  • The position of the modifier mesh will be incorrect for the following workflow:
    1. Setup and complete an Optimization.
    2. Select a result from the optimization table with a modifier mesh.
    3. Invalidate the results (by changing the Infill Density, for example).
    4. Save the project.
    5. Open the project. Upon opening, the position of the modifier mesh will be incorrect.