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JonathanHodgson13-Aquamarine
13-Aquamarine
February 1, 2019
Solved

Mass calculation using different density value

  • February 1, 2019
  • 3 replies
  • 5282 views

A colleague is struggling to make some parts report the correct mass. This appears to be because, no matter what settings or parameters we change, the mass properties report ignores the material density, or an assigned density, and continues to use a value of around 0.067 kg/mm^3 (which, for those of you not familiar with that unit set, means that our 2 foot long bit of ~5/8" pipe has a mass of around 10 ton(ne)s).


We've tried using Define Properties by 'Geometry and Density' as well as 'Geometry and Parameters', and setting the density value in that window, by assigning a material, and by changing the parameters MP_DENSITY and PRO_MP_DENSITY directly. Nothing seems to take effect.

 

The part was originally created by a client, and they have some macros to assign material properties - this may or may not be relevant.


Any clues, please?

Best answer by rreifsnyder

You mention that your pipe weights around 10 tons. Was it created using piping? If so, then it ignores the material properties set this way and instead uses the weight/length in the Line Stock when you redefine it.Capture.JPG

BTW, watch the units that you might get from suppliers, they might be Kg/meter but remember your model units.

3 replies

M
MartinHanak24-Ruby III
24-Ruby III
February 1, 2019

Hi,

is the following option set in your config.pro file ?

mass_property_calculate automatic

J
JonathanHodgson13-AquamarineAuthor
13-Aquamarine
February 1, 2019

Yes, at least when I test it on my computer; and in any case, this should not affect the results shown in Analysis -> Mass Properties as I believe they are updated directly.

S
23-Emerald III
StephenW23-Emerald III
23-Emerald III
February 1, 2019

We've had users who make the mistake of adding the mass parameter in the model tree of an assembly and assuming that it is reporting mass in the units of the assembly. I suggest not to use the model tree display of mass but use the mass properties or go to file- prepare-model properties-change- then generate report.

Open the parts individually and under file-prepare-model properties verify units, density and the "calcuation source" which should be "geometry and density" if you want the part geometry to drive your mass.

 

J
JonathanHodgson13-AquamarineAuthor
13-Aquamarine
February 1, 2019

Hi Stephen,

We're working at the part level here.

 

wrong-density-1.png

Note that density × volume != mass even in this window

 

wrong-density-2.png

 

R
rreifsnyder15-MoonstoneAnswer
15-Moonstone
February 1, 2019

You mention that your pipe weights around 10 tons. Was it created using piping? If so, then it ignores the material properties set this way and instead uses the weight/length in the Line Stock when you redefine it.Capture.JPG

BTW, watch the units that you might get from suppliers, they might be Kg/meter but remember your model units.

J
JonathanHodgson13-AquamarineAuthor
13-Aquamarine
February 4, 2019

Thanks, it was indeed created using Piping and my colleague reports that using the weight/length parameter has fixed it.

Much appreciated - I haven't used Piping so wasn't aware of that quirk.

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