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John.Pryal1-Visitor
1-Visitor
September 16, 2010
Question

Relations & family tables

  • September 16, 2010
  • 1 reply
  • 4847 views

Hi all,

is there a way of driving a dimension in a family table instance? Lets say i have a cylinder 100mm long, with a diameter of 25mm which is my generic, & i have an instance that is also 100mm long, but has a diameter of 25.5mm. I open the instance & add the relation "d8=d8+0.5 & it kind of works for me, but something is not right. Both models fail to fully regenerate, i get an amber light. Plus, why do i see the relation on my generic part, even though it does not take effect. I just want the relation to be active in the instance. I want to be able to modify the diameter of the generic & know the instance will always be 0.5mm larger.

Thank you in advance

John


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1 reply

D
DavidButz1-Visitor
1-Visitor
September 16, 2010

That relation is trouble. Everytime you regenerate it will increment the value. This sort of relation can actually be used to step through something, say varying the angle of a crankshaft to make a piston cycle, but not what you want here. If I understand your situation correctly, you need an independent value you can change. For example you create a parameter called Base_Diameter and give it a value. Then use relations to set the values for the various instances relative to that Base_Diameter.

J
John.Pryal1-VisitorAuthor
1-Visitor
September 16, 2010

Thank you for your reply David, indeed, what you describe is what i want to achieve. That is a shame, being able to wite such a relation & have it work correctly would have been very useful for me.

Regards

John

D
DavidButz1-Visitor
1-Visitor
September 16, 2010

You can still do pretty much what you want, even use a column in your table for the values. For the generic you would have d8=BD, for the instance d8=BD+.5. (Shortening Base_Diameter to BD makes it easier to deal with in Relations.) Having the same variable, d8 in your case, as both a dependent and an independent variable is really not good logical form unless you are trying to do an incrementing trick like the one I mentioned above.

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