I'm wondering about how to add a reinforcing rib to a stl model with Blender. I have a shape like the one in the picture below and I'd like to add a rib that perfectly match with the inner surface which is curve.

In a CAD modeler such as Inventor there is the possibility to extrude a sketch to a face, but no idea about how to do it in Blender.

I'm able to add a cube and resize it to the approximate shape of the rib, but how to make its border to match with the inner surface of the original stl?

curves stl model

Thanks in advance for help!

  • 1
    $\begingroup$ You can extrude faces in Blender but we will need more information about imported mesh. Wireframe would be minimal. Save it as blend file and upload to blend-exchange.giantcowfilms.com $\endgroup$
    – cgslav
    Mar 25, 2017 at 22:16
  • $\begingroup$ Thanks, here's the link. I'm also interested to know the process to add this reinforcement or if there is a tutorial that can show me the way. <img src="https://blend-exchange.giantcowfilms.com/embedImage.png?bid=3019" /> $\endgroup$
    – martin.p
    Mar 25, 2017 at 22:40
  • $\begingroup$ If your object is symetrical you might start by erasing half and using a mirror modifier so you only have to do half the work. Knife project may help make a cut you can then extrude. See my answer here about a similar question $\endgroup$ Mar 26, 2017 at 5:04
  • $\begingroup$ You could add a cube, stretch it so it has the right with for the rib, use boolean operations to cut out the shape of the object and delete the parts that are sticking out on top and at the bottom. $\endgroup$
    – Ezra
    Aug 19, 2017 at 21:15

1 Answer 1


In this particular case, I think it can also be done in this way:

put the original mesh in front view, wireframe shading,in edit mode, then select just the central array of vertices,

enter image description here

then duplicate (shift-D) and separate (P => "selection") those vertices (to a new mesh)

as you see in side view, you now have a "section" object made of two "loops".

enter image description here

deleting the "inner" vertices from both loops, you can then make a single "face" joining the remaining vertices on their edges in pairs (upper and lower) using F then, after selecting all of them, make it a big "face" pressing F

enter image description here

now you can extrude this face on left and right (I would not bother using mirroring), obtaining a solid central shape that perfectly follows you original mesh curvature.

enter image description here

Then I would join both objects, and export to .stl again.


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