Warp Question

[mjsainato]

We are running a simulation on an injected part and know from experimental data that the outside surfaces shrink differently than the inside. We are assuming that since the part is held on the core that the majority of the shrinkage is occuring on the cavity side.  I know you can use anchors to set an anchor plane, but the surfaces are cylindrical.  Is there a way to set up a warp analysis that would show the different rates of shrink between the inside wall and the outside wall on cylindrical parts?

Not sure I explained this wel enough, and not even sure it is possible using Insight....

Thanks,

Mike

[Alex.Bakharev]

The effect of difference in shrinkage between the inside and outside molding surfaces on warpage is named "Differential shrinkage effect" in Moldflow language. In linear midplane and shrinkage simulations you can plot this result separately in other simulations it is not plotted but it is here.

Usually the differential shrinkage effect is predicted from the differences in mold temperature so it requires prior cooling analysis.

On cylindrical surfaces and corners difference between in-plane and thickness shrinkage leeds to some additional coreners. In Moldflow language it is called "corner effect".

[mjsainato]

Hello Alex,

I have started using Moldflow again after having to take a break due to other projects, and have been investigating the Differential Shrinkage.  I have tried adding XY plots to determine the shrinkage, but not sure if my method is correct. 

I am choosing nodes on the outer surface of the part which then shows a result thru the thickness of the part. I am not sure if the results I am getting are showing the cavity shrink only, or the combined shrink between the cavity and core.  Is there a way to separate the results to show the cavity shrink on one plot and core shrinkage on a separate plot?

[harald_goetz]

Hello Mike,

is it possible that you show your part, or a very "similar" one?

To be honest I don't get the idea behind your words exactly.

It might also help to know what kind of material (semicrystalline or amorphous?, filler like fiber etc.) you are using.

Usually the shrinkage for the core side and the cavity side should be the same until the tool opens
- this is why you should look at your tool and part temperature distribution and try to egalize this with the help of MF.

In case of fiber as filler: Other attemps are necessary. Often cooling doensn't have to much influence here.

But it really depends on your part, geometry material and process - so instead of guessing wild let us see your problem in detail.

Regards

Harald