Relations & family tables

[John.Pryal]

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

This thread is inactive and closed by the PTC Community Management Team. If you would like to provide a reply and re-open this thread, please notify the moderator and reference the thread. You may also use "Start a topic" button to ask a new question. Please be sure to include what version of the PTC product you are using so another community member knowledgeable about your version may be able to assist.

[DavidButz]

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.

[John.Pryal]

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

[DavidButz]

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.

[John.Pryal]

Hi David,

what you have just described is what i have been trying to do for the last hour. I could be wrong, but when you write a relation with family tables you see it both the generic & the instance. It would appear that the last relation written, overrides the first, i end up with both the generic & the instance with a dia. of 25.5 instead of 25 & 25.5. Thank you very much for your help thus far, i don't want to be a pest, but if you have any further thoughts, i would appreciate them.

Regards

John

[DavidButz]

Hi John,

Sorry about that; I didn't really think that through carefully enough relative to the way a Family Table works. You really need another intervening parameter.

Here's how I made it work. Create 3 parameters, A, B, & C, create the relation A=B+C, and the relation d8=A. Set B to the value of the generic diameter, C to 0.0, and add the parameter C to the Family Table as a column. Now set the value of C for the instance to 0.5 and you should get what you want. (I hope!)

David

[John.Pryal]

Bull's-eye!! thank you very much David, that is exactly what i wanted to do, i was concerned about having to enter the same value twice for parameters A & B, but that is not the case, because of the second relation, it locks parameter A, so only B needs a value. In fact, you have opened up all kinds of possibilities for me with this, i have been working with relations for a while now, but never with parameters, & never combining the two. Thanks once again.

Regards

John