How to read mass? [fixed]
- Thread starter sz0k30
- Start date
bigseb
Alibre Super User
Its the centre console for a Star Destroyer... *groan*
Yeah! That's what I thought. 2.6 million pounds is a bit high. 26 pounds is closer to the real weight. The assembly is made up of steel, wood & plastic pieces. I was pretty sure I went thru all the part files and had the correct materials, default densities and all english units (lbs).
Looks like I'll have to go thru it all again.
Looks like I'll have to go thru it all again.
simonb65
Alibre Super User
Just create a BOM table and add a mass column, see which one looks massive!
Houston, we have a problem!!!
I just went thru and checked all the individual (16) files. The materials & mass were all correct. I manually added them up & came up with a total weight of 24.7373 lbs. Then Simon, I followed your suggestion and created a BOM table and again the total weight came out to 24.75 lbs. This assembly has 2 sub-assemblies, their weight came out correct. So where does the extra 2.6 million come from?
I just went thru and checked all the individual (16) files. The materials & mass were all correct. I manually added them up & came up with a total weight of 24.7373 lbs. Then Simon, I followed your suggestion and created a BOM table and again the total weight came out to 24.75 lbs. This assembly has 2 sub-assemblies, their weight came out correct. So where does the extra 2.6 million come from?
HaroldL
Alibre Super User
I generally don't have a Mass column for any BOM tables I might use but this issue piqued my interest. So I went thru the assembly and added material to each part. Then I added a Mass column to the BOM table for my assembly. Now back on the drawing there is NO DATA in the Mass column, However, if I add a Weight column then each parts "mass" is listed in the Weight column and the Mass column is asking for Custom Data. What gives with this? 
Also, like sz0k30, in my assembly the total Mass = 1.443203966E9 lbm but my BOM table in no way totals to that. So where is the extra weight/mass coming from?
And is there a way to show a total for the weight/mass at the bottom of the table?
Also, like sz0k30, in my assembly the total Mass = 1.443203966E9 lbm but my BOM table in no way totals to that. So where is the extra weight/mass coming from?
And is there a way to show a total for the weight/mass at the bottom of the table?
Hunter
Senior Member
Something is seriously wrong here...
Below cube is 1m^3, density of 1000 kg/m^3, so its mass is 1000 kg (or 1E3kg in E-notation). The surface area is correct, design summary too.
If I edit the root assembly, and inspect Physical Properties, I get a mass of 2E9 kg. It should be 2 x 1E3 kg = 2E3 kg. So it is 1E6 times 'heavier' (more mass really) than it should be. Out by a factor of a million. Design summary, volume, surface and CoM is correct. I didn't check mass and inertia moments.
I'll submit a ticket, this cannot be.
Below cube is 1m^3, density of 1000 kg/m^3, so its mass is 1000 kg (or 1E3kg in E-notation). The surface area is correct, design summary too.
If I edit the root assembly, and inspect Physical Properties, I get a mass of 2E9 kg. It should be 2 x 1E3 kg = 2E3 kg. So it is 1E6 times 'heavier' (more mass really) than it should be. Out by a factor of a million. Design summary, volume, surface and CoM is correct. I didn't check mass and inertia moments.
I'll submit a ticket, this cannot be.
Last edited:
Lew_Merrick
Guest
It probably means that your Material Properties values in your Parts are improperly set. One group I work with "defaults" to a Density of 1 kg/cm³ -- and then wonders why their "mass" is always wrong! "2.68536....E6" = 2,685,369.534 lbs. -- Lew
No Lew, the material properties in my part files are correct. They are the default values from the Material Library per the materials I am using. The problem is Alibre. A 26 pound assembly should not weigh 2.6 million pounds. My original post was more an issue of not believing my eyes.
HaroldL
Alibre Super User
It'll be interesting what the response from Support will be and if there will be a hot-fix for it now or rolled in to v23.
Odd that this didn't come up during Beta testing.
In going thru some of my other assemblies, I found one that has about 25 different parts, some of which are used multiple times. It appears to have the correct total weight. So checking 3 large assemblies (for me at least), 2 had very incorrect & ridiculous total weights, while one had the correct weight.
danwilley
Member
Just to add another data point... I just did a physical property check on one of my assemblies (a steel fabricated weldment) and the weight V22 calculated is the same that was calculated in V21.
About 147 pounds. Extremely close to the actual prototype's weight. The actual prototype is a little heaver but has several extra pounds of weld that are not accounted for in the model.
About 147 pounds. Extremely close to the actual prototype's weight. The actual prototype is a little heaver but has several extra pounds of weld that are not accounted for in the model.