Assembly Mass Not Calculating Properly

[t.vanmiddelaar]

Hi All,

We've had some trouble when calculating the totall mass of an assembly in Inventor.

When using the Physical iProperties, we rarely get a correct/usable mass value. The picture below states this assembly weighs 17823kg. We know this to be incorrect.

On the drawing (.idw) of this assembly, the mass states 30603kg.

The property used here is from the Physical iProperties. So, I would expect the same value.

When exporting the bom to excel, and adding up all the mass values from each part and assembly, we get 30712kg. So very close to the value on drawing.

Note: We do have some imported step-files in the assembly. These parts we have given a mass-override. Does this affect the weight calculation?

Does somebody have any knowledge how the mass is calculated? What mass number should we trust?

Thanks in advanced.

Thom

[Curtis_Waguespack]

Hi @t.vanmiddelaar , my guess is that the issue is with the imported part.

This is an excerpt from an email from similar issues I ran into in the past. Hopefully this will resolve this for you and provide some insight into the issue. But without seeing the models, I'm just guessing that this is the same issue.

Hope that helps,
Curtis

----------------------------------------------------------------------------------------------

So the issue is with the part file ( not the assembly)

Steps to resolve:

• Delete the part from the assembly
• Edit the part and set the Mass to be calculated (clear the input and hit enter)
• Place the part back into the assembly
• Edit the part and set the mass override again
• return to the assembly, and now it works?????

Q: Why did this happen?

A: Not sure, but I did notice a couple of things:

• This is an imported part, with an imported body that might need some repairs ( due to automatic, but poorly translated faces, edges, etc.) 
• If I move the End Of Part Marker to above the featured Named JOIN1 and then back down the Direct Edit feature gives an error

Not sure why this is happening, but it's likely related to the Mass issue.

It might be worth doing a Repair Body on the JOIN1 feature.

This will not fix the Direct Edit, but I think if you now fix the Direct Edit feature, the imported body will be stable going forward and not cause issues.

So maybe this is just something to do for all imported bodies such as this before using Direct Edit and overriding the mass??? Its something to watch out for anyway.

Select Find Errors > choose the body > click OK > Click the Finish Repair button

[johnsonshiue]

Hi! Please follow Curtis' suggestion. If it still does not work, please share the Inventor files here. The forum experts can help take a look to understand the issue better.

Many thanks!

[t.vanmiddelaar]

Hi Curtis and Shiue,

Thank you for your replies. This method did not work however. 

I can not send the assembly files here, because the P&G zip-file exceeds the maximum file size of 71mb.

I do think it has to do with the imported parts. I've sent this part in the attachment.

The feature "Repair Bodies" does not show in the imported parts. The feature tree looks something like this:

Is there a method to fix this part? or do you suspect that the method of import is wrong?

[johnsonshiue]

Hi! Many thanks for sharing the ipt file! This has something to do with the fact that the ipt file was a substitute part for an assembly. When a part is designated as such, its mass prop will be totally driven by the assembly unless the substitute feature is deleted. Here are the steps to restore the mass prop.

1) Go to 3D Model tab -> Modify -> expand the panel -> Copy Object -> window-select the bodies -> output = Repair Environment.

2) Delete the Derived Assembly node.

3) Edit the Repair Environment -> Find Errors -> select all bodies.

4) Heal Errors -> select all bodies. Exit Repair Environment.

5) Go to iProperties -> Physical -> clear out the overridden mass -> assign a material style -> Update.

The mass will be calculated normally.

Many thanks!