So I've put this basic body shape together, and am trying to import it into Alibre so I can shell it and add features. I can't do anything with the imported body because there are "convexity points" (many, like more than 20) along the two sweeping curves that make up the saddle shape, with the blend between.

I've tried changing the blend, moving the saddle shape, to no avail.

Can anybody help?

Thanks!

Select all the surfaces and use the Join tool to make them into a solid - at the moment they are just unconnected surfaces, so there is nothing to hollow out or shell.

I did the above and exported to ViaCAD, where it shelled OK for me.


Martin (2).

OK, got it. I did that and now my export is a solid somehow missing the blended surfaces (the band of material between the main body and the saddle shape.

I selected all of the surfaces in the file you posted here, including the blended section and it joined without a problem.
Are you sure you selected everything and did MoI display it as a Solid in the top right hand corner of the screen whilst it's selected?


Martin (2).

Hi Garet
I joined all surfaces then Moi says that's a solid
then shell 0,1 inches but i've seen artifacts inside the shell
so i cut your blend surface and redid the blend choosing G2 option and 1 value
then joined all surfaces,obtain a solid and shell:now is OK





spessore=thickness

M

Hi, thanks for taking a look.

It's not the joining that's the issue, it's the result of the exported "solid".

I've attached an igs file here of this exported MOI model. When I import this into Alibre, the blended surface is missing, resulting it a part that's not solid.

Thanks... but this is the issue I'm having. I went back and blended using the parameters you suggested, but when I join them to a solid and export that solid, Alibre throws errors saying it's found "convexity points" in the model, and all of my modifications in Alibre fail.

I shelled the part in MOI, but there were nasty artifacts inside the part. Shelling outward (flip) seemed to smooth things out in MOI, but the export still had a bunch of errors preventing me from using it in Alibre.

I don't Know Alibre,maybe you can try to export in different format
Here is your solid shelled in 3DM and also exported in IGES

Try this one Garet..

Hi Garet, I'm not really sure what Alibre exactly means by "convexity points"... Sounds like some kind of low level error being reported from their geometry library.

But when you export as IGES format, what actually gets exported is a bunch of individual surfaces and then it's up to the receiving application to rejoin those surfaces together back into a solid. Because of this often times it can be better to use STEP format for a transfer like this since those transfer solids information in the file and can avoid joining problems.

But each of these CAD formats can have their own separate kinds of quirks and problems, so if you run into a translation problem with one particular format, it's a good idea to try a different format to see if it can avoid the particular problem at hand.

I've attached a STEP file which I created by just importing your posted IGES file into MoI and then exporting as STEP format, does it work better for you?

Also when you do an import there may be various options like "enable healing" that you can turn on or off, sometimes it can be good to try switching those settings on or off to see if that has any effect.

Just in general it's probably better to try STEP format first before IGES.

- Michael

Unfortunately this one throws those same "convexity" errors.. You raise a good point about igs files. I'll go .stp from here on out when exporting solids.

The Alibre issue is that, once imported, I cannot *do* anything with the model in terms of shelling, adding bosses, and so on, presumably because of these errors it's finding. That's with as much healing and tolerant importing as Alibre can do.

Maybe I'm not generating the model right in MOI...

I still got an error, but the number of "convexity" points is reduced from 30 or 40 down to one! Did you by chance do anything to the model itself? Would you mind letting me know the steps you took?

Thanks

Note: On the Alibre forum, Ralf explains how to highlight the model in MoI, and copy paste the MoI solid into Alibre, then do "stitch to solid" in Alibre, in the surfacing menu. It sure makes it easier, with a clean(?) model.
Iges and Step files are not needed for importing, with this method.
Anyway, I'm still practicing and learning.

Hi Garet,

> I still got an error, but the number of "convexity" points is reduced from 30 or 40 down to one! Did you by chance
> do anything to the model itself? Would you mind letting me know the steps you took?

Nope, I didn't do anything to the model, I just opened up the IGES file you had posted and re-exported it to STEP format.

There is not any general special term in these file formats for "convexity points" - that's some kind of error that's specific to Alibre or its geometry library and so I don't really have any information that I can give you myself about that kind of error, you will probably need to contact Alibre to get more information about what that means and what might be done to avoid it.

I did test that step file going into ViaCAD ok, which uses the same geometry library as Alibre so I would have thought it would also go into Alibre... Here I've attached an .sat file saved out from Alibre, maybe that will go in ok since it's in the ACIS geometry library's native format.

Also does doing copy/paste like Brian mentions above work for you?

- Michael

I want to give some enlightenment, about the " Accuracy" -> "Very High" vs "High" :-)

Spatial
Edge has convexity Points

Quote
A convexity (change) point on an edge is where there is a change of convexity of the edge in relation to the two adjacent faces. Imagine two faces meeting along an edge. If there is a point on the edge where the faces meet in a convex orientation and another point where the faces meet in a concave orientation, there must be a point between these two points where the convexity changes from convex to concave. That point is a convexity (change) point. Examples of tangent edges, convex edges, concave edges, and mixed-convexity edges are depicted in Edge Convexity.

An edge is considered to be insane if it contains a convexity change point (because it is impossible to blend or offset such edges). When edges are checked at check level of 60 or greater, an Error message will be produced if the convexity of any edge changes in its interior: that is, if there is a point in the interior of the edge at which the convexity changes.
Quote
http://doc.spatial.com/index.php/HowTo:Resolve_%22Error:_Edge_has_convexity_points%22

Important:
When edges are checked at check level of 60 or greater, an Error message will be produced if the convexity of any edge changes in its interior: that is, if there is a point in the interior of the edge at which the convexity changes.

An Accuracy check with "Very high" -> The level is greater than 60.




An Accuracy check with "High" -> The Level is less than 60.

But, for daily work:
A check with: Medium or Low is (far) sufficient. ;-)

:-) Did a google translate of "surface edge convexity inflection point", also of "insane." (To German)