BOM center of mass repeat region - location according to top level default csy.

[SweetPeasHub]

I have a table with a repeat region for a BOM with materials masses and COG information. The COG is being reported from the part level and is according to the part default CSY.

What is the best way to get the COG information tabulated according to the top level assembly default CSY?

When doing mass properties analysis this information is given and it is in the top level CSY and units, but it is not recursive and I don't know how to get this information according to the assembly CSY into a repeat region even for flat assemblies.

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MASS PROPERTIES OF COMPONENTS OF THE ASSEMBLY
(in assembly units and the XXXXXXXXX.ASM coordinate frame)

DENSITY MASS C.G.: X Y Z

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repeat region variables I have been using:

&rpt.index, &asm.mbr.name , &asm.mbr.PTC_MASTER_MATERIAL, &asm.mbr.pro_mp_mass[.7], &asm.mbr.pro_mp_cogx[.1], &asm.mbr.pro_mp_cogy[.1], &asm.mbr.pro_mp_cogz[.1], 

[Chris3 · Accepted solution]

I don't know about repeat regions, but to get the analysis -> Mass properties to do this you have to turn on this config:

mp_calc_level all_models

Other configs you might want to consider:

mp_analysis_default_source assigned
force_upd_assem_mp_in_simp_rep yes

The way I do this is I have a repeat region that dumps level and descriptions and then I try and marry that with the mass property report. Its frustrating that PTC doesn't give you all of this information in one place. You can use PRO_MP_MASS but if your users didn't update that parameter at the time of release then it is going to be wrong.

[SweetPeasHub]

Thanks! This config option looks like a good solution for me. My question was too much down the road that the repeat region was the answer.

mp_calc_level all_models

 I also use this option to keep mass up to date.

mass_property_calculate automatic

[Chris3]

mass_property_calculate automatic is too heavy a performance hit on large assemblies for us. We also have lots of released parts that get modified using that config but then the users have no way of checking them in.

[tbraxton]

Would you see an advantage to calculating the mass props within the part with respect to the default assembly csys rather than in assembly mode? In general, I would do this calculation in part mode so that I do not have to have the assembly in RAM to get the results. Depending on how large your assemblies are this may not be an issue.

If you see benefit to doing the MP calcs in part mode, then you can use the measure transform tool to place a csys in the part that is congruent to the default assembly csys when the part is in situ.

[SweetPeasHub]

Generally my assemblies are not that high of a component count unless someone puts a populated 3D PCB in.

I do see a slight performance hit with the regenerations to keep mass up to date but not too bad. Maybe a mapkey could be used to initiate the update on demand. I used to use the measure transform matrices for getting secondary csy locations copied independently into subcomponents but there is an even easier way which is pretty cool if you want to know about that one I will snap a video which is the best way to show the simplicity of the process. I have also done csy that were the reverse transform that allows an imported model to be transformed so its default csy is correct for the overall assembly. (body coordinates) I guess I can say I am in automotive parts and the overall assembly is generally in the vehicle body coordinate system.

[tbraxton]

I am always interested to see alternate solutions to such problems. If you want to describe it in writing before taking the time to make a video, I will let you know if I grasp the methods or need clarification.

In a past job, I designed mobile phones at Motorola and we did impact analysis of the entire phone in ABAQUS to predict drop test failure modes. For fidelity in the sim we used fully detailed product designs which did tax multicore compute servers dedicated to running simulation. It was not unusual for PCB assemblies to have 500+ parts on them with full mechanical geometry and properties to replicate the solder joints etc.  

[SweetPeasHub]

35 second video... I am working on upping my game in video area anyway.

new csy, click csy to copy, click default csy in active part and bingo the transforms automatically update.

(I used to do csy from *.trf file after measuring to get the transform matrix)

[Chris3]

This is the better way to do it. Using the transform matrix causes rounding issues and for angles that have a long throw distance those small rounding issues can have a measurable error.

[SweetPeasHub]

Yes, when using transformation matrix always set to best accuracy.

[tbraxton]

That is nice and streamlined compared to using the measure transform. I was not aware of this method being an option. How long has that been supported? Is it documented in the help files?

[SweetPeasHub]

I have no idea on documentation as I just stumbled onto it.

[pausob]

AFAIK, it has always been a hidden feature in the GUI - this "magic" of re-defining the 6 parameters for placement and orientation for a (placed) CSYS by selecting the reference coordinate system after.

Keep in mind that the precision of the 6 offsets is related to the current setting for default_dec_places and there might be an unexpected rounding-off error.

For illustration, I work in mm and so typically, I have the setting default_dec_places equal to 3.  So if I try to specify displacement of, for example, 0.0007, system will round it out to 0.001: