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Filling up small cracks between solids

Filling up small cracks between solids

Filling up small cracks between solids

(OP)
Hello All,

I am trying to align 2 solid bodies so they intersect without forming small-area faces.
Then my goal is to combine them in a single volume and avoid "cracks" or short sticking-out edges.

What is your strategy on that?

I thought of:
1) build edges that coincide with the crack edges (here is a problem, because some of these edges are curved)
2) fill surfaces
3) close all fill-surfaces and create a solid volume inside the crack like a "tooth filling"
4) combine all voulmes

Any ideas?...

RE: Filling up small cracks between solids

Can you post an image?  Lots of ways to attempt this.  Are the voids inside the combined solid or only along the edges?  You might put a plane to the side of the surface that will be joined and then extrude material up to that body to fill in extra material--and then join.

 

Jeff Mowry
www.industrialdesignhaus.com
A people who value security over freedom will soon find they have neither.

RE: Filling up small cracks between solids

(OP)
I will try to post an image
The voids are along the edges. If one solid is extruded, I guess it has to intersect the other but without leaving its boundaries (this will create short edges and small faces atht stick out)

RE: Filling up small cracks between solids

jpolihro,

I'm not sure I fully understand your situation, but you might have good results with the Delete Face command (Insert, Face, Delete).  You can use this with the "Delete and Patch" (default) option checked to remove little slivers of material or to fill in voids.

May not be applicable in your situation - can't tell without a screen shot.

RE: Filling up small cracks between solids

Are you sure you have a model geometry problem and not some sort of model display resolution issue?

RE: Filling up small cracks between solids

(OP)
Thanks for your suggestion; I will try to get to a machine with SolidWorks and get a screenshot

RE: Filling up small cracks between solids

(OP)
Yes, I have a geometry problem. I need the volume exported into GAMBIT (a computational fluid dynamics preprocessor) and it keeps rejecting my volumes due to short edges, slivers, wrong geometry on faces etc.
All the time I do Tools/Check in SW and get no error messages from SW. GAMBIT is more sensitive though.

RE: Filling up small cracks between solids

The problem could be with the import function of GAMBIT rather than the export function of SW. SW does not (in general) have a import/export "precision" variable like some other CAD systems.

cheers

RE: Filling up small cracks between solids

Possibly a loft between the two surfaces?

RE: Filling up small cracks between solids

(OP)
From SW I export ACIS(*.sat) and feed this into GAMBIT. Honestly, I would LOVE to have this solved by adjusting precision var in GAMBIT. I am afraid that when I start meshing, these geom problems will matter.

Mostly I see the short edges appear between 2 solid bodies I am trying to join

RE: Filling up small cracks between solids

(OP)
But you're right, I have lofts betw 2 surfaces there

RE: Filling up small cracks between solids

Do you see the "short edges" in SW or GAMBIT?

cheers

RE: Filling up small cracks between solids

(OP)
in both, just SW doesn't complain about it.
Once I do Tools/Check/Short egdges 0.001m then they show up.

RE: Filling up small cracks between solids

Whoa--that's awfully small stuff.  I'd have a hard time arguing with GAMBIT in that case.

 

Jeff Mowry
www.industrialdesignhaus.com
A people who value security over freedom will soon find they have neither.

RE: Filling up small cracks between solids

I was wondering if this issue was related to a mesh generation package.  Those edges aren't that small, but I can see where a mesher would barf on them if the overall size of the model is significantly larger.

You might just have to resort to rebuilding your geometry in a fashion that eliminates the short edges/slivers, as painful as that might be.  You will probably end up with subtle differences in the geometry, but you're going to end up with an approximation of your geometry once you mesh it anyway.

Do you have any cleanup tools (merge edges, etc.) within GAMBIT?  That might be your best bet altogether if the option is there.

RE: Filling up small cracks between solids

(OP)
Yes, I've tried the cleanup tools but they either produce new errors or warp the model beyond reasonable limits

RE: Filling up small cracks between solids

Can't you use one part as a tool to cut the other part?

Cheers

Greg Locock

SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Filling up small cracks between solids

"here is one example where misalignment produces slivers"
Why is there misalignment? What is causing it?

Perhaps I'm missing the problem and over-simplifying, but the intersecting portions could be trimmed off with a plane or surface passing through the common intersecting points.

cheers

RE: Filling up small cracks between solids

(OP)
Problem solved:

I managed to avoid cracks by changing my model and then formed an assembly, used mating to constrain the positions of the bodies. In particular, I chose 1 face on each solid and forced these faces to be "coincident" with opposing normal vectors. Then by using the magnifier I was able to adjust the needed edges so that they became coincident with high degree of precision.

Mostly, the answer of the issue was:
1) form an assembly
2) do mating

Thank you for all suggestions.

RE: Filling up small cracks between solids

You weren't using mates before your last post ?????
How were you aligning parts?

Why do you need to use the magnifier to "to adjust the needed edges so that they became coincident with high degree of precision"?

cheers

RE: Filling up small cracks between solids

(OP)
Sorry if I forgot to mention I am a newbie to SW :):)

RE: Filling up small cracks between solids

Mates can (and should be) used in both assemblies and multi-body parts.

cheers

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