Fixing STLs

From ProtoLab Wiki

Many programs may be used to fix an STL; Netfabb, Magics, Mesh Mixer, Rhino. Netfabb is an AutoDesk product available for free to students through their .edu email address and as such will be the main focus of this article.

Netfabb


The following article has been written for AutoDesk Netfabb 2017 Standard.

Import Parts

Import an STL into NetFabb.
Import a CAD file into NetFabb.
To import an STL into Netfabb:
To import a CAD file into Netfabb:


Automatic Part Repairs

Import an STL into NetFabb.

Repair mode can be entered by clicking the red cross in the top tool ribbon. From repair mode there are several fields of significant importance; shells, border edges, invalid orientations, and holes. These are all technical issues with the STL and are not functions of your part. There should be 1 shell per continuous part, 0 border edges, 0 invalid orientations, and 0 holes.

Netfabb's automatic repair tools can be used to fix these problems in most scenarios:
  • Click Automatic Repair in the lower part of the Netfabb part tree.
  • Click either Default Repair or Simple Repair in the pop-up window. This may take some time to complete
  • If your part does not have 0 border edges, 0 invalid orientations, and 0 holes attempt another repair.
  • If your part now has 0 border edges, 0 invalid orientations, and 0 holes click Apply Repair. There are other tools to reduce shells to 1

It is not recommended that you use the extended repair. This repair wraps the visible surface of your STL in a new mesh. This repair can lead to thin regions of your model which is of particular concern if plan to use the zPrinter 450.


Boolean Operations

Import an STL into NetFabb.
In the event an automatic repair cannot merge your part down to 1 shell you may:
  • Adjust your Rhino file so there is 1 closed polysurface per part before meshing or exporting as an STL.
  • Mesh your model in Netfabb by importing the CAD file instead of an STL.
  • Use Netfabb's boolean operations to reduce the mesh to 1 shell.

The boolean operation button can be found in the top tool ribbon. It appears as green and red circles intersecting one another.

Netfabb's boolean operations tool can be used to reduce a mesh to 1 shell:
  • Shells may be added or removed from the tools consideration by moving them between the green and red columns in the part tree.
  • Click the green cross to begin the boolean union. This may take some time to complete
  • Once complete click the the blue check to apply the operation.
  • Recheck the model in repair mode to confirm there is only 1 shell.
If the Boolean union command fails to merge down to one shell it is likely that the shells are disjointed and will print as separate parts:
  • Enter Repair Mode by clicking the red cross in the top tool ribbon.
  • Click Shell Selection in the top tool ribbon.
  • Select different parts of the model to see the different shells.
  • If you can clearly see the disjointed parts return to your CAD files and attempt to fix your geometry.
  • To select hard to find shells press Ctrl+A to select all shells.
  • Deselect the main shell by pressing Ctrl+left click.
  • Press Delete to remove the extra shells.
  • Inspect your geometry for any deformations.
  • If your part now has 1 shell, 0 border edges, 0 invalid orientations, and 0 holes click Apply Repair.


Export STL

Import an STL into NetFabb.
When repairs have been completed you will need to re-export your model as an STL:
  • Select your model.
  • Right Click
  • Select Export as STL

As a reminder, your STL must have 0 border edges, 0 invalid orientations, and 0 holes before exporting and should have 1 shell per continuous part, and 1 part per STL. Failure to follow these guidelines could result in a failed 3D print.