** WARNING 305320 ** Excessively high polymer temperatures

[Anonymous]

hi friends

I have prepared my model (3D mesh of hor runner attached to the part as single file) and meshed it nicely (coarser mesh in non-interested area and finer mesh on the runner and gate location, total of 1.5 million element). the part is a thin walled injected PET mold. I have run the Fill + Pack analysis but in the analysis log I notice there is this warning:

** WARNING 305320 ** Excessively high polymer temperatures have been reached in some regions

A temperature limit of 788.00 F will be applied.

the warning has happend at time below which corresponds to the time when melt flow reaches the narrow gate at the part.

|----------------------------------------------------------------------|

| Time | Fill Vol| Inj Press | Clamp F | Flow Rate| Frozen | Status|

| (s)     | (%)     | (psi)        |(ton(US)) | (in^3/s)     | Vol (%)|           |

|----------------------------------------------------------------------|

| 0.415 | 8.003 | 9.535e+03 | 1.71e+01 | 29.415 | 1.03 | V |

Could it be because of the extensive shear heating effect at the gate? is it normal in practice to have local high temperature zones in the flow?

any advise or input is appreciated.

[inba.oneway777]

hi,

heck whether shear heating is a problem, especially in the gate region.

Check excessive heat as a result of sudden polymer flow after a valve opens.

Check the mesh for problems, such as extremely distorted elements.

[kristen.kilroy · Accepted solution]

Hello Mike,

The warning message you are seeing, Warning 305320, is typically related to shear heating, as you had mentioned. Moldflow's solver uses a limit of the "max melt temperature"+100 deg C to trigger this warning. If it reaches that maximum, it is most likely due to very high shear rates on the material. This can be due to either the geometry or to the mesh. I would suggest (as Inba suggested) to review the mesh you have around your gate. Specifically, review if there are any high aspect ratio elements internally. If the mesh is acceptable, the high shearing is most likely due to geometry. 

Please let me know if you have any additional questions, as I'm hapy to help. 

Regards,

-Kristen

[Anonymous]

Hi i have the same warning.

Which are the maximum acceptable values for:

maximum aspect ratio

Maximum dihedral angle

for a 3d mesh to avoid the warning?

Thanks.

Regards,

Matteo

[kristen.kilroy]

Hi Matteo, 

In the following forum post, one of the mesh developers (Shoudong) helps explain the recommendations on mesh aspect ratios: 

• Moldflow Forum Post: Aspect Ratios

For this specific warning, checking the aspect ratio reduces risk of calculation error resulting in the high shear rates caused by the high aspect ratio.  As mentioned in my previous post, this can also just be a result of the geometry and how shear heating of the flowing plastic is occuring as a result of the flow paths.

Hope this helps! 

Regards,

[mppkumar]

Hi

As explained this issue may be because of poor mesh (high aspect ratio)

but don't restict yourself only to meshing error... this may be due to the part geometry

as a best practice, try to maintain aspect ratio of tetras less than 50