Rib from round edge

amir_livne

Hi
I'm trying to build a rib from a round edge but I can do it only when the line is not at the edge.
I understand that there is a problem with the round edge.
I'll appreciate if someone can give an idea to handle it

EvanReese

I think the issue is that if you put the rib right up to the edge the corners of the rib would hang over the edges. you could use an Extrude or Loft or Sweep perhaps if you want the edge of the rib to match the circle exactly.

romeograham

Another trick would be to use the Rib feature as you have done, and then use Replace Face (replace the face of the rib with the curved face of the part) or the Move face feature (to move the face of the Rib up to the curved face of the part).
This allows you to still use the Rib feature.

bruce_williams

@romeograham
I think the OP has an angled rib like on this doc.  I am not understanding how Replace or Move Face can be used.  Could you please explain more?

Thanks!

Henk_de_Vlaam

What we need is a so-called Profile rib. See this (Creo) video at minute 4:00 (https://www.youtube.com/watch?v=083RQmSn6mY&t=240s).In Onshape I have a workaround for that:
1. Make the rib via Revolve.
2. Replace the 2 flank faces of the rib with an offset from the sketch segment
   
   
   
   
https://cad.onshape.com/documents/e51377d5946c9f26f8c4fc95/w/bb28cfc559312e726531793e/e/789f28aede42b11f568b66bd

romeograham

@bruce_williams - I was thinking that the revolved lower portion of the part had a face that could replace the upper face of the rib - you're right: it won't work with geometry like you're showing.

I like @Henk_de_Vlaam's suggestion to use the sketch for an offset face replace operation on a revolved feature.

bruce_williams

@romeograham thank you. I agree @Henk_de_Vlaam’s work around is best or just live with rib being back from the edges a bit

romeograham

@bruce_williams That's right. And we haven't even gotten into the realities of dealing with the surfaces and transitions at that location: where are the rounded edges that will result from some type of production technology? How will the part be made? Will draft or inside rounds be needed? etc etc.

The design intent captured by the CAD is part of the story - the other part is what is actually being produced, and are there any additional factors to be considered as a result of making the part into a physical thing.

Henk_de_Vlaam

romeograham said:

I like @Henk_de_Vlaam's suggestion to use the sketch for an offset face replace operation on a revolved feature.

In this way I also split a complicated sketch in two or more sketches.
For the sketch plane of the (second) sketch that must remain related to the first, I always choose a sketch segment from that first sketch.