Shadowspawn
Aerospace
- Sep 23, 2004
- 259
Hi folks,
I've just been tasked with writing up a short paper describing the various reasons that drawing dimensions get unassociated, in an effort to cut down on the amount of re-detailing that is involved by the drafters. I'd like some input from the community as to my suppositions, as well as any reasons that I have missed, and some possible solutions.
My reasoning is basically as follows: Dimensions typically become unassociated because the unique ID that the dimension uses to the feature that it's attached to has been deleted:
1) The designers/modelers are creating the models in a less than efficient manner with respect to future changes. Either sketches aren't being used, or are used in a manner that isn't conducive to changing (too complex, confusing, using obscure geometric constraints, etc). Thus, when a change comes along the person updating the model winds up blowing away the original feature(s) and re-creating what is needed (thus hosing the dimensions/drafting objects associated to tthese faces/edges).
Solution: Sketches should be simple and straight forward with the minimum amount of complexity required and with some thought put into the 'design intent' before hand. Arcs shouldn't be used in sketches when a later blend will do, Never use the 'fixed' geometric constraint and minimize the 'point on curve' constraint.
2) No realistic effort is put into updating the existing features as required before deleting and re-creating the feature(s). All too often I've seen EC's come through and bosses, blends, pockets, etc. are deleted and re-created when simply modifying the feature would have been preferable and thus would allow the drawing to update without re-associating the dimensions.
Solution: Don't delete features...modify them when possible.
3) Utilize centerlines to dimension to, not the arc center of a feature. Quite often I've found dimensions associated to the arc centers of features and not to centerlines. It's easier to re-associate a centerline than it is to re-associate a mass of dimensions.
Solution: Dimension to centerlines associated to arc centers, or axial centerlines associated to a cylindrical face and not the arc centers (ie section cuts).
4) Blends blow up during updates, and are thus deleted and re-created (with unknown consequences to the drawing).
Solution: Prior to deleting the blend, reset your current feature to the blend and re-associate the edges defining the blend. Walk through the model updating blends as necessary. Refrain from blending the part until last, using edge blends before resorting to face blends.
5)Much of the problems associated with un-associated dimensions could be alleviated by checking the electronic file for adherance to existing standards and approved modeling methodologies. The 'anything goes as long as the drawing depicts what we want' attitude and culture must change.
Solution: Enforce standards and change the existing culture so that the electronic model is the document of record versus the plot of the drawing. Checking and enforcing standards and methodologies will get everyone doing things in a more congruent manner, even if the methodology is less than ideal.
These are just a few that have popped to the front of my noggin, I'm sure there's loads more reasons. So how do these sound and can you think of any others? I'm looking forward to your response and TIA...
SS
I've just been tasked with writing up a short paper describing the various reasons that drawing dimensions get unassociated, in an effort to cut down on the amount of re-detailing that is involved by the drafters. I'd like some input from the community as to my suppositions, as well as any reasons that I have missed, and some possible solutions.
My reasoning is basically as follows: Dimensions typically become unassociated because the unique ID that the dimension uses to the feature that it's attached to has been deleted:
1) The designers/modelers are creating the models in a less than efficient manner with respect to future changes. Either sketches aren't being used, or are used in a manner that isn't conducive to changing (too complex, confusing, using obscure geometric constraints, etc). Thus, when a change comes along the person updating the model winds up blowing away the original feature(s) and re-creating what is needed (thus hosing the dimensions/drafting objects associated to tthese faces/edges).
Solution: Sketches should be simple and straight forward with the minimum amount of complexity required and with some thought put into the 'design intent' before hand. Arcs shouldn't be used in sketches when a later blend will do, Never use the 'fixed' geometric constraint and minimize the 'point on curve' constraint.
2) No realistic effort is put into updating the existing features as required before deleting and re-creating the feature(s). All too often I've seen EC's come through and bosses, blends, pockets, etc. are deleted and re-created when simply modifying the feature would have been preferable and thus would allow the drawing to update without re-associating the dimensions.
Solution: Don't delete features...modify them when possible.
3) Utilize centerlines to dimension to, not the arc center of a feature. Quite often I've found dimensions associated to the arc centers of features and not to centerlines. It's easier to re-associate a centerline than it is to re-associate a mass of dimensions.
Solution: Dimension to centerlines associated to arc centers, or axial centerlines associated to a cylindrical face and not the arc centers (ie section cuts).
4) Blends blow up during updates, and are thus deleted and re-created (with unknown consequences to the drawing).
Solution: Prior to deleting the blend, reset your current feature to the blend and re-associate the edges defining the blend. Walk through the model updating blends as necessary. Refrain from blending the part until last, using edge blends before resorting to face blends.
5)Much of the problems associated with un-associated dimensions could be alleviated by checking the electronic file for adherance to existing standards and approved modeling methodologies. The 'anything goes as long as the drawing depicts what we want' attitude and culture must change.
Solution: Enforce standards and change the existing culture so that the electronic model is the document of record versus the plot of the drawing. Checking and enforcing standards and methodologies will get everyone doing things in a more congruent manner, even if the methodology is less than ideal.
These are just a few that have popped to the front of my noggin, I'm sure there's loads more reasons. So how do these sound and can you think of any others? I'm looking forward to your response and TIA...
SS
