×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Feature Dependencies and Good Modeling Practices

Feature Dependencies and Good Modeling Practices

Feature Dependencies and Good Modeling Practices

(OP)
When in sketcher and adding dimensions, SW seems to only allow dimensioning and adding relationships from edges instead of allowing you to choose an entire surface.  This causes errors and can cause the model to fail when the edge is eliminated (i.e. adding a round or chamfer).  Am I just a SW rookie or is there a way to constrain feature to more stable geometry such as planes like good modeling practices in ProE?  BTW I am using SW2003.  Thanks.

-Joest

RE: Feature Dependencies and Good Modeling Practices

In general you can dimension or make relationships to planes.  Sometimes you need to select the plane in the feature tree.  It depends on what you need.  I find that sometimes it is appropriate to use edges and sometimes not. Due to the chronolgical nature of the SW database, even if you change an edge later, the original sketch will still be fine.  It is only if you make an edit to something earlier in the file that you would have an issue. It should show up as a parent to the sketch containing the dimension or relationship.

John Richards Sr. Mech. Engr.
Rockwell Collins Flight Dynamics

A hobbit's lifestyle sounds rather pleasant...... it's the hairy feet that turn me off.

RE: Feature Dependencies and Good Modeling Practices

If a plane is normal to the sketch then you can dimension to it.  You can not pick a face to dimension from.

Your are right, dimensioning to a face would be more robust.

RE: Feature Dependencies and Good Modeling Practices

(OP)
Thank you all for your input.  I dimension to planes when they are available.  My goal was to find a way to dimensioning to faces.  TheTick confirmed that SW does not allow that.  I guess I will have to live without it.  There are pro's and con's to any software.

Cheers

-Joest

RE: Feature Dependencies and Good Modeling Practices

The reason is what TheTick indicated and I forgot to point out.  The face would have to be A). perfectly flat (or maybe circular) and B). perpendicular to the sketch plane to make logical sense and give a non-ambiguous result.  Planes are by definition dead flat.  Surfaces would have to be interrogated on the fly to confirm they were suitable to dimension and would cause a real problem if edited later to change their shape or orientation.

John Richards Sr. Mech. Engr.
Rockwell Collins Flight Dynamics

"Heck, there are so many rules around here, it's hard to accomplish anything!" - Me.

RE: Feature Dependencies and Good Modeling Practices

As JNR stated earlier, SolidWorks features are time-dependant (ie, their "chronolgical nature").  One of our company's best practices is to keep all fillets/rounds at the bottom of the feature tree in order to keep the model from failing when edges are eliminated.  
If a feature needs to be added later, use your roll-back bar.  It's like going back in time!

RE: Feature Dependencies and Good Modeling Practices

(OP)
JNR,
Yes, you are correct, dimensioning to surfaces wouldn't work unless A) and B) are true.  SW will not allow these dimensions even when both condition true.  In ProE, it is possible because it is a feature based software which makes it a more robust package.  I'm not too concerned with it, it just good to be aware so I don't devote further resources looking for a way to do it.  Thanks for the help.

-Joest

RE: Feature Dependencies and Good Modeling Practices

Just as a mattter of interest, you can select faces when dimensioning a 3D sketch.

from Barrie, Ontario.

For Sale: Parachute. Only used once, never opened, small stain
FAQ559-863

RE: Feature Dependencies and Good Modeling Practices

(OP)
That's good to know.  Thank you for the tip.  Do 3D sketches have any limitations (drawbacks) that would keep one from using them by default?

RE: Feature Dependencies and Good Modeling Practices

There are some things you just can't do in a 3D sketch: sketching circles, equal length constraint, and symmetry constraint for starters.

"Great ideas need landing gear as well as wings."--C. D. Jackson
http://www.EsoxRepublic.com

RE: Feature Dependencies and Good Modeling Practices

The main issue here is that SolidWorks is a surface based software, not feature based.  Therefore you can't dimension from features.  You can only dimension from edges of the surfaces that were created by the features and of course datums axis, etc..  If that surface or edge is removed by another feature later in the model, Solidworks can't figure out where the orignal surface or edge is.  The original surface doesn't exist as far as SolidWorks is concerned.

This doesn't help but at least it may help explain why.

RE: Feature Dependencies and Good Modeling Practices

(OP)
alexsasdad,
The fundamental issues are clear now.  So far, not being feature based is the biggest (-) I have found about SW.  are there any benefits to being surface based as far as functionality is concerned?  It seem like it is done solely to speed up the software calculations and simplify the code.  I guess this is what separates a mid-range application such as SW and a high-end package such as ProE.

-Joest

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources