Cavity weight

[Anonymous]

Hi there,

I'm quite new to Moldflow Insight. I have a question about cavity weight:

After running an analysis (fill & pack), I look at the volume of the cavity and the density. When I calculate this 'by hand' (volume * solid density) I end up with a heavier product than Moldflow will return. Does this have to do with the difference between solid and melt density? I can imagine packing pressure and time has an impact as well? 

With kind regards,

Martijn

[bernor_mf · Accepted solution]

@Anonymous 

Hi Martijin,

yes, you are on the right path of the reasons for the difference.

The injected melt will shrink when cooling to solid, so actually a smaller volume.

There will always be a difference comparing cad model weight = cad model volume x solid density 

( or meshed model weight = meshed model volume x solid density)  vs

simulation result and weight.

This as simulations starts with a melt (melt density) to fill a cavity, and where weight is related to volume melt entered into cavity, packing pressure, and how long packing can be applied when part is freezing and runners are freezing.

You could look up the material data and PVT-curves, to get an understanding of underlying behaviour.

The packing in analysis is by default 10s and 80% MPa of injection pressure.

This affects result, and should be adjusted accordingly for the time available to pack, and pressure level as well.

Sometimes better to control packing pressure level in absolute number.

Hope this helps.

Regards,

Berndt