Sketcher referencing options

[TheNorseman]

NX 9.0

Is there a way to reference plane surfaces of existing geometry in sketcher (without creating datum planes through the existing geometry)? From what I know now, I'm only able to reference edges and vertices of existing geometry. For example, if I have a 1x1x1 cube and my goal is to put a hole through it at .250 from the bottom surface and .250 from the side surface. In sketcher, I can only place dimensions referencing the edges of that cube, not the actual surfaces. I don't see this as being very stable because that edge can be eliminated with a chamfer, blend , or some other feature later in the model. I've also noticed that in drafting mode, you CAN select surfaces to dimension from which leads me to believe that somehow, this referencing option may exist in sketcher...thoughts/suggestions?

I'm relatively new to NX, coming from 15+ years of Pro/E. In Pro/E, I could simply add any surface of existing geometry that I want as a reference...I'm just looking for the NX equivalent to that. Thanks in advance for your feedback!

~Brian

 

[JohnRBaker]

Yes, you can select a planar face as a sketch plane but the Datums that get created are part of the Sketch feature itself and are not actually extra geometry (they're not shown in the Part Navigator).

As for the issue of referencing an edge that might get removed as the result of some later operation such as adding an Edge Bland or Chamfer, that dosen't cause any problems. The sketch still knows about the referenced edges even though they may no longer be part of the final topology of the model. See attached simple example to see what I mean.

Coming over from most any other system generally requires that you will need to unlearn some of the things that you did or did not do before. I think you will find that NX will allow you do thinks in a much more flexible and forgiving manner than what you previously experienced.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Digital Factory
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

 

[TheNorseman]

Thanks for the feedback, John, but I was wondering about whether or not it is possible to use existing planar surfaces as references inside the sketch.

For example, if you're already inside your active sketch and you place a dimension from the first reference(which would be the center of the circle), to the second reference (which is what I'm questioning). If you look at the model I uploaded, I placed two similar sketches of circles, but I used different references to place the dimensions. In the first sketch, the horizontal dimension references the center of the circle and a datum plane that I created using an existing planar surface of the cube;(the vertical dimension was created the same way). In the second sketch, the horizontal dimension references the center of the circle and the edge of the part;(the vertical dimension was also created the same way). Then I added a chamfer feature and a blend feature at the end of the part. Now, if I drag the chamfer feature or blend feature to precede those two sketches, I'll get an error/warning message on the second sketch because the system can't find the edge that I used as reference. However, the first sketch remained stable because of the datum plane that were referenced from the existing planar surfaces. Now, getting back to my question...when I am inside my active sketch, is there a way I can reference existing planar surfaces without having to create datum planes? Thanks again for your help!

~Brian

 

[TheNorseman]

...

 

[JohnRBaker]

Not that I'm aware of. The sketcher is looking for curves/points/datums and that's about it.

As for the failure when you reordered the blend/chamfer feature, that's the expected behavior since by doing so you're changing the 'history' of the model such that the edges were no longer in existence when the sketch was created. So if this is going to be an issue with the way you plan to edit/update your models, then yes, it's a best-practice to add whatever additional references objects, in this case a Datum Plane, to assure that there will always be something that can be referenced irrespective to how later features are edited or reordered.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Digital Factory
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.