Undercut auto-recognition function for clamping force calculation accuracy

[peter_hwang]

Hello! I'm Peter with Moldflow technical support in Korea. Recently, I have written a technology development request that many customers are requesting.

Nowadays, the shape is complicated by the development of plastic products with many functions.

Because of this, if "undercut" is not detected and the "Exclude clamp force option" is not selected, a clamp force calculation error will occur. As shown in the figure below, the undercut part has to cancel the clamping force due to the offset of internal pressure.

  Moldflow developers can help prevent this error. Please develop a function that automatically detects undercuts! If you think you need this feature, please support us.

[bernor_mf]

Hi @peter_hwang  ,
I second this idea and agree.

This has been raised before:

automatic undercuts surfaces exclusion from clamp force calculation

It was commented as "Used to be there in a prior version of the 3d flow code."
So some work seems to be done on this.

And this was "Accepted" about 6 years ago!

Time to get it in to the software.

Regards,
Berndt

[raalteh]

Hi Peter,

As @bernor_mf mentioned, this has been raised more than once before. The correct solution is actually not all that easy.

The full 'cancelation' of forces is only true when the plastic pressure is 'uniform' (hydro-static), which is roughly OK the moment the cavity is filled. But it would be quit off for instance before the part is filled (where you have a high pressure at the gate and 0 pressure at the flow front. 

 

Also ... we currently do not have in the model where the parting line lies, which ends up being important.Below you see a few different (maybe impractical) configurations of the model you used, that would actually give different clamp forces in reality. We normally do not have this type of information in the model.

Not to complicate things further but there are also slider configurations possible where the 'horizontal' pressure on the slider would be transferred vertically, adding to the clamp force. And in the current model there is no way to rally account for this.

We will eventually I suspect be able to get and be able to solve this using 'core deflection' but it would likely be incredibly computationally expensive. 

For the time being, the user would probably be best served by using exclusion from clamp force in the best possible way, though it's not going to be perfect.

There are similar complexities with stack molds by the way.

Hanno

[bernor_mf]

@raalteh 

Hi Hanno,

thank you for clarifying the situation and status.

Years ago I worked on a script to automate to find elements to exclude from clamp force for Midplane/DD mesh..

Simple algorithm, based on a node position, and very slow...

Would be great to have a tool that helps to select elements to exclude from clamp force.

Moldflow Adviser, Design Adviser, has the Undercut result, with undercut and shadow features.

Having that as a starting point could be helpful, I think.

Regards,

Berndt