Meshing perforated aluminum

SOFiSTiK Rhino
1

Hello,
I’m currently working on a perforated Aluminum sheet ~50% perforation. I modeled it in Rhino and used grasshopper to create the holes. Now I’m running into the issue meshing it. I can’t get Sofistik to mesh all the inner edges. I’ll put a picture of the Rhino Modell, the Sofistik output and the start of the msh.dat in here.

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HEAD Netz Generierung
CTRL TOPO 0
CTRL TOLG -0.01[m]
CTRL MESH 1
CTRL HMIN 0.005[m]
CTRL EFAC 10.2564
CTRL FINE -0.46
CTRL PROG 1.4

sar 1002 grp 1 mno 1 nra 7 qref ‘CENT’ t 0.002[m] mctl ‘auto’ titl ‘SAR 1002’ NX 0.000000 -1.000000 0.000000
GUID ID “c24e36e8-7305-4185-bf37-479f0351426f”
sarb OUT
slnn s 0.0000000000 degr 3
slnn s 0.0000000000
slnn s 0.0000000000
slnn s 0.0117989608
slnn s 0.0117989608
slnn s 0.0117989608
slnp x -0.5656865363 0.0000000000 0.9000000000 1.0000000000
slnp x -0.5696195232 0.0000000000 0.9000000000 1.0000000000
slnp x -0.5735525102 0.0000000000 0.9000000000 1.0000000000
slnp x -0.5774854971 0.0000000000 0.9000000000 1.0000000000
sarb OUT
slnn s 0.0000000000 degr 2
slnn s 0.0000000000
slnn s 0.0142749452
slnn s 0.0142749452
slnn s 0.0285498903
slnn s 0.0285498903
slnn s 0.0428248355
slnn s 0.0428248355
slnn s 0.0570997807
slnn s 0.0570997807
slnn s 0.0607924597
slnn s 0.0607924597
slnp x -0.6106865363 0.0000000000 0.9000000000 1.0000000000
slnp x -0.6123219931 0.0000000000 0.8925896279 0.9131496376
slnp x -0.6078973527 0.0000000000 0.8864243305 1.0000000000
slnp x -0.6034727123 0.0000000000 0.8802590332 0.9131496376
slnp x -0.5959287276 0.0000000000 0.8794364581 1.0000000000
slnp x -0.5883847430 0.0000000000 0.8786138830 0.9131496376
slnp x -0.5827353799 0.0000000000 0.8836807391 1.0000000000
slnp x -0.5770860167 0.0000000000 0.8887475951 0.9131496376
slnp x -0.5770860167 0.0000000000 0.8963362929 1.0000000000
slnp x -0.5770860167 0.0000000000 0.8981899256 0.9941079297
slnp x -0.5774854971 0.0000000000 0.9000000000 1.0000000000

2

the errors/warnings I get from sofistik are the following:

+++++ error no. 638 in program DO_Check_Region
Definition of structural area 1002 is incorrect (boundary not defined counter-clockwise)
+++++ warning no. 696 in program DO_Zerteil_2
Unable to generate a pure quad mesh in structural area 1002 (triangle 13).
Affected region has been triangulated locally. Mesh size should be reduced in structural area 1002.
+++++ warning no. 699 in program DO_Zerteil_2
General error occured while meshing region 1002
+++++ warning no. 696 in program DO_Zerteil_2
Unable to generate a pure quad mesh in structural area 1002 (triangle 15).
+++++ warning no. 694 in program DO_Zerteil_2
Unable to generate a pure quad mesh in structural area 1002 (triangle 10048).
Affected region has been triangulated locally. Mesh size at structural edge 1105 should be reduced.

3

Your mesh might be too coarse in certain locations.
Try:

  • Adjusting Ctrl Tolg (intersection tolerance, your lines are maybe so close that they are overwritten)
  • Adjusting Ctrl Hmin/Ctrl Fine/Ctrl Prog/Ctrl Efac (max element size/refinement/progression)

Basing this on the Affected region has been triangulated locally. warnings

The incorrect boundary error might either be due parts being deleted (intersection tolerance) or the code actually defining the boundary in the opposite direction.

Just looking at the code:
You are defining everything using NURBS → mathematically advanced way of defining geometry
Might be easier defining it with straight lines and semi-/quartercircles (SLNB instead of SLNN/SLNP)
Depends on how you have defined your geometry though.

4

Thanks a lot.

  • Adjusting Ctrl Tolg (intersection tolerance, your lines are maybe so close that they are overwritten)

Did the trick, trying to mesh 5mm intersections with a 10mm tolerance doesn’t work that well.
(Though I also scaled it down to improve computing time)