Orientation effects on results

[bob.schlosser]

Hi all, 

I have noticed that how a model is oriented slightly affects the results of an analysis.  I had originally thought the orientation was only used to determine the clamping plane to calculate press tonnage.  The analysis I ran was a simple hollow rod with the gate in the center of the part.  Does anyone have any insight as to why this would affect the results?  Do the effects of orientation make a greater difference on a complex part?

Thanks

Bob

[Anonymous]

Bob, the orientation (rotation in Moldflow terms) should only affect the clamp tonnage. Any other effects is either an error in the model or a bug in the code.

Can you post the model so I could chek it?

[yannick.moret]

Remember the warpage plot is a "out of plane" plot and by default we choose to look at out of plane for XY plane, and so in Z direction.

So the way you orient your part, the warpage color plot might be different.

But if you use anchor plane, then the out of plane warpage plot will be dependant of this anchor plane and not of the global Z direction of your part.

No other resutls except clamp tonnage should be affected by the orientation of the part.

If you see slightly different results for other results, it might be due to the pre-processing of the part being influenced by the orientation.That can happen especially if the part is big on 1 direction only.

You can try to use high resolution analysis to see if differences get smaller.

Regards

[bob.schlosser]

Here is the model and results file. The part was left to default processing conditions and was copied and rotated 90 degrees once the gate was placed. The results are nearly identical, but are different. For a computer program I would expect things to be identical if orientation didn't matter. I want to understand why the results are not identical and if this would have any affect on a more complex 'real' part.

For example, the pressure drop differs by 0.003 Mpa. Not much, but why does it change? This question has been asked of me and I can't give an answer. I need to be able to defend the results that Moldflow is generating.

[Anonymous · Accepted solution]

Hi, Bob 

I was tested your model with 2013 and cannot reproduce the problem. I have imported the test.sdy from your zip file, changed the sequence to fill-pack-warp with all the default parameters and run the simulatiuon. After this I have rotated the whole model by 90 degrees over X axis and run the analysis for the new model. The models and studies are attached.

Comparing the results by the "compare study" tool gives only three differences: Names of the result files, Projected Area and Maximal Clamp Tonnage.

I  thought that maybe the difference in pressure is too subtel for the Compare Study tool to pick but the log files themselves (see atttached screenshot) show no differences.

The only difference I could notice was a subtle difference in deflections:

while the maximal deflection is the same: 0.2569 mm, the minimal deflection is 0.1080 for the original model and 0.1074 mm for the rotated model. As Yannick said this subtle difference is probably to postprocessing of the best fit. Do not worry about it.

I an thinking that a small difference in the peak pressure you have obtained might be due to a slightly different matching. Before doing the analysis of a dual domain model the software have to do some geometrical processing - determine thickneses and matching elements. Every release Autodesk Moldflow makes some improvements into this process. Matching takes some time, so the solver is trying to save the info in the study file once it done and redo the matching only if the model is changed. If a model was first matched by an older version of an AMI and then rotated then the new model would be matched by the new version of the software. Also in the past the matching by GUI (done to play some diagnostic plots or during importing of CAD models) might be slightly different from matching done by the flow solver - I believe it is fixed now. The difference in matching might account for a very subtle difference that I would not worry about.

[Anonymous]

The forum software did not allow me to post the whole project. I have attached the two study files I have used.

[bob.schlosser]

Thank you for putting the time and effort into this reply.  This doesn't look to be anything to be concerned about.