Alternative center of mass

[Suslik1987]

Hello everybody i work with Nx 8.5

It is possible to set an alternative center of mass to a part withte funktion analyse -> advanced mass properties -> advnaced weight management. In an assembly with parts which have a calculatet center of mass and parts which have a fixed centr of mass the center of mass of the assembly will be calculated right. But the center of mass of the assembly can only be see in an information window (x,y,z cooridnates) in the option advanced weight management.
There are no possibility to make this point associative to an other point. I have found no opportunity to make an expression to the center of mass coordinates from the information window. Is there any posibility to make this coordinates associative to an expression?

Thanks and best regargs

Suslik1987

 

[JohnRBaker]

Yes, but not until NX 9.0 when we added a new 'Measure Point' function that gives you expressions which represent the X,Y,Z coordinates of any point that you can select, including the point associated with the Center of Mass from a previous 'Measure Bodies' calculation.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Digital Factory
Cypress, CA
Siemens PLM:
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[Suslik1987]

Thanks, but with the measure bodies function i have only the possibility to measure the center of mass for the visible geometry, what is if i have a simple body which doesn't represent the detailed model. In this case the measure body function uses the geometry of the simple body althougt i have set the center of mass to a specific point...

Is there a solution too in NX 9 or Nx 10

 

[JohnRBaker]

Have you looked at...

Analysis -> Advanced Mass Properties -> Advanced Weight Management...

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Digital Factory
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

 

[Suslik1987]

Yes of course i use this function to give a standard part an alternative center of mass.
But in my assembly are parts that have an alternative center of mass like standard partswhich are not design exactly and parts that have a center of mass which will be calculated by the geometry of the part. Now i want to get the center of mass of the whole assembly. For this i can`t use the function meassure bodies...i would get the false center of mass.

So i use this function:

Analysis -> Advanced Mass Properties -> Advanced Weight Management...

But here i have not the possibility to make the center of mass associative... because i get the information only within an information windwow. There are no expression which are set or something which i could use to make a point associative with...

I hope you understand my problem...

Thanks

Suslik1987

 

[cowski]

This reminds me of a procedure we used years ago to get the overall weight and CofG of an assembly; we didn't have an advanced assemblies license. Some of what we did was to help speed up the weight calculations on larger assemblies (thank goodness for today's faster computers). I don't know if this will help you at all, perhaps it will spark some ideas. Anyway, FWIW, here is the procedure:

[ol 1]
[li]set the density of the body according to the material to be used in manufacturing[/li]
[li]measure the body, make note of the COG and weight (it wasn't associative at the time)[/li]
[li]create a point on the COG, create a sphere with a volume of 1 unit³ (we worked with inch files, the resulting spheres would be a bit tough to work with in metric!)[/li]
[li]set the density of the sphere equal to the weight of the body; this way its weight would equal the body weight[/li]
[li]create a reference set named "CG", place the point and sphere in the ref set[/li]
[/ol]

When we wanted the assembly CG/weight, we'd switch the component reference sets to CG and analyze the assembly (the spheres acted as simplified bodies to speed things up). We had a grip program set to run on every save that would update the sphere CG for us; still, getting the assembly CG was a bit tedious.

Perhaps you could use the "sphere" idea to create a body with the CG and weight you want and use it in the weight calculations. I believe there is an option in the advanced assemblies weight management to use a certain reference set for the weight calculations. But, I don't have extensive experience with the weight management functions, so perhaps I'm in left field...

www.nxjournaling.com

 

[Recon1775]

I have the exact same issue as Suslik1987.

I need a point or CSYS to be generated using the Asserted Values applied from the Advanced Weight Management function.

Can a CSYS or Point be created with the run of the Advanced Weight Management function with Asserted Values, similar to how Measuring Bodies creates an associated feature?

(Using NX 9)

Thanks!