How to check for errors when measuring assembly weight, COG, inertia, etc.? 3

[msjoey]

Hi everyone.

First of all... DISCLAIMER: I haven't used V5 for years so I will need explicit instructions if you can provide me some, thanks

My aim is very basic, I just need to check the COG of a hood assembly of a 4x4. It seems pretty simple. Just apply the right materials and mech properties to each part in the assy, save the results / files, and then ask V5 to measure the inertia of the whole assy. I get results and the COG looks to be where I and the designer would expect it to be, except that the weight is way off. Total weight is more than 3,000 kg when it should be about 200 kg.

I have checked the part list one by one and there seems to be no duplicates. Except for three sub-assy that are already deactivated. Material density for each material file I created is correct.

My question: what else should I check for? What is causing this excess weight? Can I trust this COG (I don't think so) and pass the coordinates to the designer?

Thanks in advance,
Jo

 

[ferdo]

Hi,

Are you using SMD workbench ? It will measure also the developed part....

Regards
Fernando

https://picasaweb.google.com/102257836106335725208

https://picasaweb.google.com/103462806772634246699/

 

[DBezaire]

There is an Only Main Bodies check box on Measure Inertia. This will take into consideration PartBody only.

This check box is also available on the Mechanical tab in the property page of the part/product.



Win 7
23SP5/24SP3, 3DVIA Composer 2015

 

[tbuelna]

It is usually best to apply the material properties to the top level of a part. It is also best to only have a single body in each part. Make sure all of the parts in your product are in design mode. Check that every part has a material applied with the correct density. And lastly, make sure you have the product active when you make the analysis, and that your analysis results are based on the proper axis system.

 

[msjoey]

Hi everyone,

First of all thanks for the responses. I have resolved the issue and obtained sensible results by working around the problem.

I searched old eng-tips thread and found this useful post:

http://www.eng-tips.com/faqs.cfm?fid=679

Then I followed the instructions for "Calculating assembly weight". I reopened the single parts one by one and jot down the weight for each part. I found one part that had the extra weight (3,000 kg), saved it as stp file, opened the stp file, saved it as a new CATPart, used the new CATPart to replace the old CATPart that had the crazy weight value. Now the whole assembly has the correct weight when I remeasure inertia.

I checked the old CATPart with the crazy weight and still has no idea what caused it. The designer hasn't applied any material before sending it to me and there are no duplicates. It's weird. But at least now I have the correct weight.

cheers,
Jo