Point onto point parameter creation 1

[Candas]

I would like to learn the reason why NX creates a parameter called "positioning dimension parellel distance set to zero" when positioning with point onto point.

Since the point that the feature will be attached is already positioned for an appropriate design , in my opinion that parameter must not be visible to users(like geometrical constraints_coicident or concentric).

Thank you for your comments...

 

[JohnRBaker]

Because that is exactly what the software has done. It was felt that there was no need to create a special type of constraint, just a way to automatically assign it. What a point-on-point constraint does is create a parellel dimension that has a value of 'zero'. No different than point-onto-line creates a Perpendicular dimension with a value of 'zero'. This is just the result of reusing constraint concepts that were already in place rather then creating a new concept that would have added no real new value.


John R. Baker, P.E.
Product "Evangelist"
NX Product Line
UGS Corp
Cypress, CA

http://www.ugs.com

 

[DavidTolsma]

Why use positioning dimensions at all? There are better and more importantly easier to understand way to constrain things.

-Dave
PLM Exchange

http://plmexchange.net

http://groups-beta.google.com/group/NX_CAX/

 

[Candas]

Hello Dave,

Do you prefer modelling by using sketcher?

Regards,

Candas

 

[DavidTolsma]

Candas,

Depends on the design. Usually I will use Sketcher but I may have started out with curves then put them into a sketch.

For example if I'm laying things out conceptually, I will probably draw flat out curves, until i get something I think will work then constructing the model off of that. As soon as I need to drive anything by a rule I will put it into a sketch.

I never liked positioning dimensions, mostly because they where always kind of hidden and you couldn't access them from sketcher. Exiting out of sketcher change the positioning dimension then going back into sketch was a waste of time in my mind so I never looked at them again. That was many versions ago. Never ran into a corner because of it either.

Not to get too far off the subject I like to model by defining relative datums. Those are my critical design points and the model hangs off of those object. Along with Mating conditions are all done by datums. Those mating datums are driven by the same expressions that drive the model. The model can completely change and there is no issue of face ID's changing causing mating conditions to fail. A little complex but it's bullet proof.

-Dave
PLM Exchange

http://plmexchange.net

http://groups.google.com/group/NX_CAX/

 

[phillpd]

Rather than create "positioning dimensions" in the Sketcher, you can always create "regular" Sketch dimensions to the external geometry. That way, when in the Sketcher everything is there to see.

Paul Phillips
Specialty Engineered Automation

http://www.sea4ug.com

 

[mjcole]

Even with NX2 I once used positioning dimensions for a fixed point in a sketch and was able to also put dimensions for the same point from within the sketch which seems kind of strange. Maybe this was due to a bug that's been fixed.

I'm wondering if there has been any improvements such as showing the existing placement dims in sketcher or in the expressions tab on the navigator.

Michael