3D or Dual Domain

[mark.e.bessac]

While reading through many 3D questions on the site, I am wondering if many people are analyzing true thick and chunky design parts, or just using the 3D?

When I run side by side 3D/Fusion on normal wall thickness (typically 2.00mm-2.5mm) parts I get quite different results with respect to pressures and deflections. With some, the actual flow varies quite a bit. Which analysis type to believe?

So far, even when running 3D on these parts, it seems like the best prediction. Should I even go down this road, or just stick with the Fusion?

Are other folks using 3D independent of geometry type?

Thanks!

[nishit78]

I use 3D for almost everything, but then many of my parts need 3D.

The only time i used 2D is for thin wall part with very large surface areas (for eg. thin-wall tub-like parts). For such parts, to get a decent 3D mesh quality (6 layers with other mesh quality requirements) is very difficult unless the dd mesh is quite fine, and then the element counts are enormous. But if i could i would use 3D as much as possible.

Just my opinion.

[PascalGosset]

I use Moldflow since a long time. I stud more than 100 parts a year.

Normaly, I make the simulations with 3D only when it is necessary : thick parts, overmolding of inserts ...

For ordinary parts, I think the 3D do not gives betters results than Dual.

Except, perhaps, for the shrinkages predictions.

With 3D, sometimes I found visibly false results.

By example, a filling clearly unbalanced whereas the mesh was absolutely symmetric.

Recently, I noticed big differencies between the warpage calculated with the Dual mesh and the 3D (values +50 to +80%).

For the same part, with another material, I got quite similar results with the 2 meshes (pressures, warpage).

In fact, the material shinkage data are not the same for these 2 kinds of simulations.

That's life...

with Moldflow.

[MikeHoyt1335]

I also run a ton of simulations a year and I aggree with Pascal  on this .

3d is usefull when using inserts /ovemolds ( and what I call cosmetic parts .. if thicker walled )

We have found DD'd to be closer to reality with thin ( 1, 2 or even 3mm walled) parts.  

[nishit78]

I dont think part thickness is the only criteria for DD. It is the ratio of flow width to flow thickness. This can be a little difficult to evaluate for certain so-called thin wall parts.

I work on several parts in the thickness range of 1-2mm but they are not necessarily classified as thin wall parts (especially for moldflow) because the width of the flow front at any given time is not sufficiently wide w.r.t. the thickness to justify a dual domain. I think that the mesh match diagnostic captures this logic in some sense but yet nothing beats visual check. Mesh match can sometimes be mis-leading based on the nature of the part design.

Using DD is fine but as long one can be absolutely certain that the part is truly a thin walled in moldflows terms.

Having said all this a little deviation from this (thin wall desgination) does not do much harm (in my exprience)

[tim.vanast]

I use 3D for everything I can.  Even large 2mm flat parts.  The rare midplane is only for large flat parts that I expect to have thickness changes like flow leaders.  I've seen too many issues with DD results that I find the results of 3D more consistent.  And in the last few versions, the 3D runs faster than the DD.  And finally, meshing is much faster for 3D than DD.  Aspect ratios of 30 are easier than 6.  And you don't have to be as concerned about mesh matching.

But I have seen the inconsistent flow down two sides of a symetric part.  But this is the exception, not the rule.

Just my opinion.

Tim

[teopado89]

Excuse me, which is the minimum good value for mesh matching in 3D mesh?
thanks

[mayur_dhumal]

HI,

Mesh match is available in ONLY Dual Domain solver. 90% is a guideline.

Regards,
Mayur

[teopado89]

Ok thanks