A sink marks doubt

[flyinthesky]

hi,i made a simulate yesterday,but there have a doubt in that simulation.The sink marks estimate result shows there no have risk of sink mark issue on the part,but the volumetric shrinkage result is unacceptable,can anyone tell me that the sink mark issue have or not ? thank you,the attachment are the results.please check it.

[bernor_mf]

Hi,

from Autodesk Knowledge Network, AKN , https://knowledge.autodesk.com/ :

How to evaluate Sink marks estimate result and volumetric shrinkage in Moldflow

The Sink Mark Depth result is calculated based on volumetric shrinkage and geometry configurations (area thickness, rib thickness, base thickness, rib height. etc.). The exact formulation used in software is confidential. For a fixed design, sink mark depth depends on volumetric shrinkage distribution in the part.

The Sink Mark Estimate solver is designed to find sink mark area under a rib or a boss. It is not intended for sink mark from estimate from a pure thick area. If a part is chunky, even if itself may have big volumetric shrinkage, sink mark estimate solver may not locate sink mark for it due to the calculation method.

Regards,

Berndt

[bernor_mf · Accepted solution]

Hi,

regarding 3D volumetric shrinkage: 

As a loose rule the volumetric shrinkage in a region is 3x linear shrinkage for that material.
Anything twice or more than 3x linear shrinkage could start to be come severe.

Whether it becomes a void or sink in a thick section depends on frozen layer thickness, the mechanical properties of the skin thickness,
and this can all be affected by the cooling rate.

If I extrapolate this, high risk starts to occur around 2x volumetric shrinkage.
But - void or sink mark?

Rapid cooling rate solidify skin, to such a skin thickness it does not deform, and then probably void is created.
Stiff materials more prone for voids than sink marks.

For the material you use: is the area of volumetric shrinkage around 2x or more compared to 3x linear shrinkage for that material?

Regards,

Berndt

[flyinthesky]

hi,the material what i used is Apec 1603,the molding shrinkage is 0.75%.Thanks for you reply.

[bernor_mf]

Hi,
create a contour of volumetric shrinkage:
Create a New plot with Volumetric shrinkage, 

and set plot properties as :

1) tab Methods : Contour - Single Contour

2) tab Animation : Animate result over:
Single dataset
Show higher values

Animate result at Time, last time step

Adjust frames as wished.

This will help to see areas of high volumetric shrinkage within part.

Regards,

Berndt