What gets extruded?

[eewoz]

Hi,
How does Alibre decide which part of a sketch to extrude? I have a project where I want to make a box with compartments in it. My first approach was to sketch a rectangle and extrude it to the box height. Then I sketched in 3 rectangles to designate the three compartments that I wanted. This sketch looked similiar to the one below except all of the lines were fully defined to length and position. I then did an extrusion removal. The result that I wanted was for the 3 rectangles to be removed, but instead the "walls" around the rectangles were removed. I eventually solved the problem by making the original extrusion the thickness of the box bottom and doing an additive extrusion to build up the walls. Is there a way to tell Atom to extrude the rectangles rather than the material around the rectangles? I use Alibre Atom.



Thanks,
Ed

 

[HaroldL]

As drawn your sketch should have extruded the walls. The inside rectangles would remove islands from the outside rectangle. You would need to add another extrusion to close the openings. If the walls were removed and all you got was the inner rectangles extruded as blocks then there is something else going on with the sketch that needs to be looked at. It may be that you included an outside rectangle along with the three inner ones. If that's the case delete the outer rectangle and update the model.

I suggest you go through the training videos for Atom 3D, accessible through the Alibre Home page, as they explain the design process from sketching all the way thru to creating assemblies.

 

[NateLiquidGravity]

When extruding; Alibre uses a method best described as islands. Meaning each loop is either the start of land or water. The outermost loop is always land. The next loop in that land would be a lake. The next loop in that lake would be an island. So on and so forth.

 

[WillB]

I then did an extrusion removal.

I think you are both missing this part of his post

 

[WillB]

Simply turn the outside lines to reference lines and it should work

 

[eewoz]

@HaroldL Indeed the walls were extruded as you are saying they should have.

I think the island-water concept explains it. It appears that Allibre starts from the outside and works inward with the extrusion process. I did as WillB suggested and made the outside lines reference lines and the rectangles extruded rather than the walls.

Thanks guys!

 

[HaroldL]

It may be that you included an outside rectangle along with the three inner ones. If that's the case delete the outer rectangle and update the model.

Whether you delete the lines of convert them to reference figures, both methods will work in this case.

 

[NateLiquidGravity]

I think you are both missing this part of his post

No, Alibre determines "what areas of the sketch to use" exactly the same way for extrude boss and extrude cut - and multiple other sketch based functions too.