Reference Dimensions

[lab2010]

What is the best way to implement reference dimensions? I use this term cautiously, but I want to use a dimension that has been changed to reference to define some other component of my model. I cannot provide a file with an example, but I have attached a picture as a simple example. Note that I realize there is an easy solution in my example, but it is just to convey my issue.

Say I draw a cone with a base radius (P1 = 100). Then based on other criteria, somewhere along that cone, I need to use the radius. If I take a vertical constraint at that point (P2), it returns the radius. The model is now over-constrained unless I make P2 a reference constraint. Now say I want to have some line offset from the cone by P2. I set a constraint (P3 = P2), and it gives the correct offset. My issue comes occurs when the radius (P1) is changed; the P2 displayed value updates but the P3 offset does not. I'm not sure why I can put reference dimensions in a formula if they do not update, but it seems that is the case. So what is the best way to reference a value that is not explicitly defined?

I thought maybe this scenario is the purpose of having an option to "use measurement" in the formula definition. However when I try to use a distance measurement in my constraint for P3, I cannot select any lines in my current sketch. The only thing I have been able to do is duplicate all of that information in a separate sketch; then when I use the distance measurement, I can select the lines and get my radius. It does update when changes are made as well. It works, but this seems to be a very convoluted way to perform a seemingly common action. Is there a better option?

Thanks in advance

 

[JohnRBaker]

Rather then create an actual constraint dimension go ahead and create the point where you want is in the sketch and then leave the sketch and use a Measure Distance (with 'Associative' option toggle ON) to get the height of the point from the axis of the cone. Now you will have to create a second sketch for the parallel line, but then use the expression created by the Measure distance to control offset of the parallel line, as I did did in the attached example.

John R. Baker, P.E.
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[patelmimnesh]

hi..
thanks and this is best for it..

Mimnesh,

 

[lab2010]

That works out well. Thanks for the advice