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Ralph_W10-Marble
10-Marble
April 30, 2024
Question

Flexible components and outdated mass properties

  • April 30, 2024
  • 2 replies
  • 2367 views

We use the PRO_MP_MASS parameter for our weight calculation and as a value on our drawing.

To ensure everybody is executing the mass calculation the setting mass_property_calculate is set to report_outdateness_only (or check_upon_save). A warning 

For normal assemblies these settings are ok.

But in assemblies where we use flexible component (e.g. a spring or a folded flexfoil) the mass properties of the assemblies keep outdated every time the assembly is opened. 

Even a bottom up mass calculation of all parts and finally the assembly will not help. Because after closing and re-open the assembly,  the assembly shows "outdated mass properties".

How to solve, or block this?

2 replies

B
BenLoosli23-Emerald III
23-Emerald III
April 30, 2024

I'm  not sure you can prevent this due to the flexible part being 'modified' when brought into the assembly.

A hose assembly modeled as 12 inches as a standalone part, when in the assembly it is now 15 inches as it follows the flexible path, it has a new mass due to the longer length. Not sure how a sping 'stretches' as a flexible part (add coils or changes spacing) but the add coils would also change the mass.

 

R
Ralph_W10-MarbleAuthor
10-Marble
May 1, 2024

The strange thing is that I already brought the flexible component into the assembly and adjust the length or folding angle. I updated the mass calculation of the assembly (and this one is correct). 

But after closing and opening the assembly again (no changes made) the mass property of the assembly is outdated. 

Somehow the mass is not stored in the assembly if flexible component is in.

 

kdirth
kdirth21-Topaz I
21-Topaz I
May 1, 2024

Using flexibility does not change the part file.  It still has the unflexed mass properties.  A flexed part in an assembly loads the original part file into memory then modifies it based on the flexibility settings, changing the mass properties calculation.

There is always more to learn.
    kdirth
    kdirth21-Topaz I
    21-Topaz I
    April 30, 2024

    You may need to use User Defined Mass Properties for any part that you intend to flex.  Even stretching a spring by changing the spacing will change the mass calculation as the diameter of the spring is not collapsing as it would in real life.

    There is always more to learn.
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