Mass Problem

[engscap]

I am assign material and measure the mass from analysis>measure body (let 20KG) , but I want to change the mass of my model to be 10KG and measure it using analysis>measure body to give 10kg instead of 20kg without change the material (were I not know the material which give this mass)

there are any Solution !!!!!!!!!!!!!!!!!!!!

 

[JohnRBaker]

One approach is to 'assert' a specified Mass to a part file which will be used instead of the computed Mass when getting the mass information of an Assembly where this part is used. This function is intended to handle the situation where you've modeled purchased parts of known mass but have no way of getting the details exactly right knowing what materials it was made from, so you can 'assert' the correct 'catalogue' mass. You could use this, but only if you have an Advanced Assemblies license. Besides, it only assigns the mass to the Part file, NOT the actual solid body, so this might not be what you're looking for.

If you want to change the mass of an actual solid where a material has already been assigned there's one approach which should work for you. First, are you working in Imperial or Metric units? If it's Imperial units (inches) then go directly to the next step, but if it's Metric, you can save some additional calculations by first going to...

Analysis -> Units kg - mm

...and change this to kg - m.

Now you can take the next step using...

Analysis -> Measure Bodies...

...and with the 'Associative' option toggled OFF and the 'Show Information Window; toggled ON, select the solid and record the displayed values for Volume and Mass. Now using these value, divide the Mass by the Volume to get Specific Density. If you're working in Imperial units you're looking for lbs/in^3 and if in Metric you need kg/m^3 (if you did not change your analysis units to kg - m as decribed above, then you'll have to first convert the volume as computed from mm^3 to m^3 by dividing the computed volume by 1000 three times). OK, once you've got your computed Specific Density, divide it by two to get the new desired value.

Now before you can assign a new Specific Density directly to the solid body you have to first remove the old material assignment. So go to...

Tools -> Materials -> Manage Materials...

...and change the top filed to 'Local Materials'. Now you should see only a single material listed and so select it and your model should highlight. Now at the bottom of this dialog there is a row of icons and the last active one on the Right should be labeled 'Remove selected material assignment' (just hover the cursor over the icon to see its label). Select this icon and then leave the dialog. The previously assigned material has been removed from the model.

Now go to...

Eidit -> Feature -> Solid Density...

...and when the dialog opens select the solid body and in the field labeled 'Density' enter you new computed density (the calculated density that you divided by two in the steps over) and hit OK. You solid model will now weight exactly HALF of what it did before when you perform any future analysis measurements.

I know seems a bit convoluted but it works.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
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