Merge ribs' end issue

[Rcer]

Hi everyone! I'm currently modelating a custom nut with a section that has an outward thread on CATIA V5, however, while trying to create this thread using the command "Rib" I'm getting the following error when I select the option "Merge ribs' end ":

"Topological Operators: impossible relimitiation on the main part. - Change the specifications"

This error is only appearing when I am working with outward threads of any size, while with inward threads I am having no issue at all. I was wondering what could be causing this problem or another method I could use to create a thread with merged ends please.

Cheers!

 

[Bouta]

What are you trying to achieve with the "Merge Rib Ends" Can you make more screenshots? I can't see many details here but that's not how this function works. "Merge Rib Ends" is used when the guiding curve doesn't end on the parent body. Ticking this option results in either extrapolating the guide or cutting it to the body boundaries.

Check it here: https://grabcad.com/tutorials/what-...n-merge-rib-ends-and-merge-ends-in-rib-option

 

[MrCATIA]

Thanks Bouta, and nice video!

 

[Rcer]

Hi Bouta! Thank you for your reply. What I'm trying to achieve with the option "Merge Rib Ends" its to create a pointed shape for the nut outward thread's leading edge (which I will then finish by applying an Edge Fillet Definition). On the screenshot you can see the inward thread I have created using this option showing the result I want to achieve for the outward thread:

Inward thread:

View attachment 2287

Outward thread:

View attachment 2288

 

[Bouta]

Ok, so it's easy, imagine that you cut the guide in your inward thread - merge rib ends extrapolates that guide by tangence - so it just adds a straight line which goes into the solid - that's why it closes. Meanwhile an extrapolated helix guide in an outward thread will just shoot into space - so it has no chance of "sinking" into the body. You need to either bend the curve downwards at the end or create that profile with a sweep and close it with "Close Surface". Merge Rib Ends definitely won't work here.