Weight

[nilza.reis]

Hi!

In the results of the studies, filling and packing, for example, the weight of the parts is different the reality.

Example: I have a part with 663cm3 - volume. The density of the material is 0.9g/cm3. Correct weight is 596.7g. Moldflow is 496.7g.

There is always a variation of 100g. Why?

I speak about the Moldflow Insight 2013.

 Thank you.

[mayur_dhumal]

Hi Nilza,

The reason behind difference of your product weight in Moldflow & reality is that you may have used different packing profiles in both the cases. In both cases if you have used the same packing profile then have you solve Cooling analysis & then again Flow analysis?

Regards,
Mayur

[nilza.reis]

Hi!

Thank you for your replies.

I use the same processing condition on the machine and the difference happens.

I use other software to calculate, for example, unigrafics and the weight of the parts are correct.

In unigrafics - correct weight

In reality - correct

In Moldflow - we have a difference of 100g.

The volume is correct in three cases. (unigrafics, reality and Moldflow)

[madhukeshwart]

1. try to add shrinkage to model and feed system and run the analysis, confirm whether it is matching expected weight .

2. Check the density plot if your running the analysis with 3d, whether the value is matching with your assumed density.

3. Try to over pack the part and check by increasing gate size and packing time. 

Just reply, if you got any other reason. 

[Halasur]

Hi

Deviation in weight is mainly due to difference in volume of CAD model and FE model. It should be nominal and to reduce the difference have to over pack to achieve desired material density.

Regards

Aravind Halasur 

[tim.vanast]

It does seem strange that the weight doesn't match.

I would check the CAD volume vs the Moldflow mesh volume.  If those match then I would check the density of the material in the database vs the data sheet.

And lastly, the calculated weight is affected, as stated above, by filling (short shot areas have no weight) and packing.

These things should add up to a correct (at least close) part weight. 

Good luck.

Tim

[maxmarautodesk]

Hi Nilza,

I agree with the previous comments and can think of several reasons that could contribute to the difference in weight. To find out I have the following ideas for you:

1. check the volume of your meshed model and compare it to the CAD model. The meshing has limited capability of reproducing rounded geometries.
2. check your mold/part dimensions and compare it to the CAD model, perhaps your tool makers have accounted for shrinkage, so that your mold cavity is larger than your CAD model or the tolerance of your mold is not met.
3. check your packing profile.
4. check the gate freeze off in the simulation. If there is a discrepancy to reality and your packing stops in the simulation before gate freeze off, material might flow back.
5. check the material entry of the Moldflow database for the used material and compare the density there to the data sheet/your measurement.

I hope to provide some inspiration. However, 100 g seem really like a huge difference...

[nilza.reis]

Hi!

Thanks for the reply.

In all studies have found that weight in moldflow does not match the result density x volume. (I have Moldflow Insight 2013)

CAD 3D and Mesh are same volumes but diferrent results for weight.

I always show the result of the weight volumeXdensity.