coolFEM - internal and external mesh size - what value do you take

[phammer]

HI, 

i would like to verify just my infos. 

What valuies do you take or are advised for meshing the mold. Especially for the internal and external.

I have the info: 

internal = half of beam length

external = 2-3 x internal

Philipp

[maxmarautodesk]

Hi Philipp,

my knowledge about this topic is based on a presentation by Autodesk from 2011 (relevant slide see in attachments).

First, to clarify the names for all users:

external = surfaces of outer boundary of mold

internal = surfaces of mold in contact with other entities such as inserts or part

According to the slides of Autodesk, it is recommended to use:

external = 3-4 x internal 

internal = I have no information

However, I usually cannot follow these recommendations and find them not very practicable. Since I have no information about the internal edge length, I try to use the same edge length as for the insert or the part in contact with the mold. This enables a) to use the "Precise match" function for the meshes and b) that the mesh ressembles approximately the original CAD geometry.. As a consequence, I easily end up with a ratio of external to internal of up to 1:10 and therefore exceeding the recommendation from above. However, if I use the internal edge length being equal to the part or insert and keep the ratio of 1:4, the number of elements for the mold shoots through the roof. If I use a decent external edge length and follow the ratio of 1:4, the internal edge looks very bad and cannot capture the original geometry properly.

I would like to see Autodesk releasing more guidelines for the meshing parameters in general. The programm became recently very complex, with different meshers and so on. The software provides default values for some of the paramters, but I still have to do a large amount of trial and error, until I get a mesh that a) has no errors and b) looks homogeneous and good to me (and this is very subjectiv, as to somebody else it may not look good, but I have no clear measures to judge).

Best regards,
Max 

[xusho]

Hi Philipp,

I would suggest:

external = 3-4 x internal 

internal = the global edge length for parts (cavity). 

Shoudong