Part mass increases when inserted to an assembly

[scotte]

Hello,
I'm having serious issues with masses increasing (6X) when inserted to an assembly. Mass will be correct when I edit the part and incorrect when added to an assembly. At first this was only an issue with imported components but today it has happened with a native AD part. The seriousness of the issue is that I'm designing a forklift and knowing the weight and CG is critical and one of the reasons I migrated to solid modeling. I hate to think I'll have to calculate this manually, as in the old days, because if we figure this out I need to come to trust ADs handling of the math.
Cheers,
Scott E

 

[scotte]

Here's more info. Some of the parts giving the most trouble are Alibre files from TraceParts. Yes, I have corrected the material properties because they import at 1000kg/cc. One example is a 20 pound shackle that 'material properties' insists weighs 64000 pounds. Anyone else seeing this. Maybe I pay more attention to weight than most.

Scott E

 

[BernardK]

I have used this feature quite a lot and never had any issue with it.

Can you post a problem part so folk here can take a look.

 

[RocketNut]

I have the same problem. :roll: A carbon fiber piece should not weight over 50 lbs (from experince) comes up will over 20000 lbs. Yes the material carbon-carbon composite is selected.

 

[scotte]

Thanks RocketNut. That makes 2 of us so far. I've been experimenting a lot (too much). To add to the uncertainty I'm not even getting consistent wrong answers. For example 271 pounds of oil will weigh 600 pounds one time and 2400 pounds another. And this is a native AD part I created. Most problems have been imported parts.
I could upload some parts, but they only misbehave inside the assembly which is too large to post. I do have plenty of computer w/ 12Gig ram.

 

[wathavy4]

I once was unsure of the assembly weight...

I made an assembly with two pieces of part. One steel and the other aluminum.
I upload it so you don't have to make it.
It seems the total weight is fine....

 

[DavidJ]

For such a potential serious issue, I think you should report this to Alibre support.

 

[scotte]

DavidJ: You are correct. I submitted this to support last night. I wanted to use the forum first because I usually get better responses and answers.

Thanks,
ScottE

 

[NateLiquidGravity]

Was this ever fixed? I am seeing some mass numbers in an assembly that don't add up.

 

[Anonymous]

This issue is still under investigation. We don't have many example files that demonstrate this behavior. Nate, would you be able to send me yours?

(Ryanm@alibre.com)

 

[NateLiquidGravity]

Unfortunately I am unable to send in this one. I did however work around the issue by making an Assembly Boolean for each material type and then adding those values together. This came much closer to what I expected so is probably correct. On a related note, it looks like Assembly Booleans select all parts in a sub assembly including suppressed parts - which is confusing.

 

[Ken_L]

I am a complete newbe to Alibre Design, and have been painfully getting used to it over the past three weeks. Two decades of 2D CAD experience haven't helped as much as I hoped!

The topic of this thread is exactly one of the issues I want to solve. In my case, I'm slowly assembling a boat as realistically as possible by carefully creating a separate part for each component, paying particular attention to the density of the material so that I can get accurate total mass and C of G. Unfortunately, even though the assembly has only two parts at this stage, the total mass reported is complete rubbish. It's as if the assembly function has no idea of part properties. Only the toal volume is reported correctly.

Is there some step in all this that I've just missed, or is Alibre not capable of providing meaningful physical data for assemblies?

 

[Lew_Merrick]

Having been somewhat knee-deep for the past couple of days, I only now got the chance to double-check this. I just tested six different assemblies ranging from 2 parts to (approximately) 300 parts using Alibre Design™ Expert 2012 Alibre Design Version PRODUCT VERSION 14,0,2,14052 ) 32-bit and I find mass properties match exactly. I am not sure how this fits into things, but I thought that the datapoint was worth reporting.

Could this be a 64-bit vs. 32-bit issue?

 

[Ken_L]

Having been somewhat knee-deep for the past couple of days, I only now got the chance to double-check this. I just tested six different assemblies ranging from 2 parts to (approximately) 300 parts using Alibre Design™ Expert 2012 Alibre Design Version PRODUCT VERSION 14,0,2,14052 ) 32-bit and I find mass properties match exactly. I am not sure how this fits into things, but I thought that the datapoint was worth reporting.

Could this be a 64-bit vs. 32-bit issue?

I am using Alibre Design Personal, but this properties thing should surely work the same no matter what edition?

I've attached the assembly as far as I've developed it to date. The "Hull planking" and "Transom planking" are two separate parts, each of which were given material properties to yield correct mass. The Hull planking weighs 129.6 kg and the transom weighs 2.1 kg. However, the assembly Physical Properties reports the total mass as 150.6 kg, whereas it should be 131.7 kg. Volume, interestingly enough, is correctly reported in the assembly.

There's not much point persisting with the assembly until this issue is sorted out - what have I done wrong?

 

[DavidJ]

You'll have to either upload the part files too, OR export the assembly as Alibre.stp file and upload that. The ASM file does not contain the parts, just the rules to combine them.

 

[DavidJ]

Ken,

Are you sure that the Transom at 2.1 kg isn't actually 21kg (displayed by Alibre as 2.1 E 1 kg ) ?

 

[Ken_L]

You'll have to either upload the part files too, OR export the assembly as Alibre.stp file and upload that. The ASM file does not contain the parts, just the rules to combine them.

OK, David, partfiles attached.

This shows how new I am to the 3D CAD game!

 

[Ken_L]

Ken,

Are you sure that the Transom at 2.1 kg isn't actually 21kg (displayed by Alibre as 2.1 E 1 kg ) ?

Sorry, David - I didn't see this post before forwarding the part files.

You have absolutely nailed the problem! I must be getting stupid in my old age, because I simply mis-interpreted the mass of the transom by a complete order of ten. To say I'm embarrased is an understatement.

Thanks for that - I can go on building the virtual boat with more confidence. It's now a race to see whether the real boat gets finished before the virtual one.

 

[DavidJ]

Happens to us all from time to time !! Glad it's sorted.

 

[scotte]

Hi all,

Was this ever fixed? I am seeing some mass numbers in an assembly that don't add up.

This was submitted to support and was resolved by replacing a file. Note this was version 2011. V2012 has worked fine for me.

Cheers,
Scott E