Adding a Relation to a Point

Discussion in 'Pro/Engineer & Creo Elements/Pro' started by LouR, Jul 12, 2005.

  1. LouR

    LouR Guest

    I wonder if someone can help me out with this. I added a "point" to the
    "Center of Gravity" in
    my "assembly". as i work and add parts etc to my assembly i would like to
    have this "point" i
    added changed as the "center of gravity" changes. I like to make a relation
    between this "point"
    and the "center of gravity", anybody know how to do this??

    thanks

    LouR
     
    LouR, Jul 12, 2005
    #1
  2. LouR

    LouR Guest

    Glenn thanks for the information. I needed the point on the CG to show its
    location in 2D so i could dimenion it.
    but thanks again for your help.

    LouR
    =============
     
    LouR, Jul 13, 2005
    #2
  3. Lou, First you need to calculate mass properties using >edit >setup
    'source' should be set to 'Geometry and parameters' , then click
    on >generate report.

    Next, create a coordinate system using the default csys as
    reference, then create a relation in the assy with the three
    dim's which referenced the csys. It should look something like this:

    d66=mp_cg_x ("","ASM_DEF_CSYS","")
    d67=mp_cg_y ("","ASM_DEF_CSYS","")
    d68=mp_cg_z ("","ASM_DEF_CSYS","")

    When you regen the model the new coord sys will update. Each time
    you change the model you need to recalculate the mass prop using the
    generate report as above. Then a regen should update the coord sys., you can
    add a point to the new coord sys if you need a point. This seems like alot
    but a couple of mapkeys and your done quickly.
    Goodluck,

    Gary Miglionico
     
    Gary Miglionico, Jul 13, 2005
    #3
  4. LouR

    David Janes Guest

    You're right, this is the classic approach to representing, in a more permanent
    way, the center of mass in a model/assembly. And it works, but not very well.
    Without some trickery on the user's part, it is always representing the COG as it
    was with the previous part added, not the latest.

    Here's why: adding a part causes a regen which moves the CSYS (or point) to the last (previous) position calculated by Generate Report. Now, you actually need to regen, again, but nothing happens automatically. You have to remember to do it. And if you don't, the position is NOT updated.

    And, it is completely ineffective in part mode. There you add or subtract a feature; part COG does changes to the value calculated last by Generate Report. But after that, there is NO FORCED REGENERATE to get it up to the value of the latest Mass Prop. That's one reason they dumped the form embodied in the relation d66=mp_cg_x ("","ASM_DEF_CSYS","") and went to PRO_MP_CGX because it would automatically update without the manual 'Generate Report'. This is available in later revs of Pro/e, from about Wildfire on. BUT, the best of all possible worlds, I repeat, is the Analysis Feature. You have to buy Behavioral Modelling to get it, but you'll be a better person for it.

    David Janes
     
    David Janes, Jul 16, 2005
    #4
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