Controlling extrusions from sketches / building a 3D solid solely through sketches

Maxpm

So, let's say I've created the following solid by extruding different sketch surfaces to different depths.

The various extrusion depths are hidden away as feature settings.  This makes them difficult to modify.  In a real project, where the proper extrusion depth could depend on other surfaces (rather than blind distances), it would be even harder.  I'd like to control the extrusion endpoints from a sketch in the front (or side) plane, partially so I can have them all in one place, but also so I can constrain them with other things.

I know I can create a sketch on the front plane and Use some edges to get this:

Which does, at least, let me constrain future geometry based on the extrusions.  But it doesn't solve the root problem of constraining, or even explicitly defining, the extrusions themselves.  I can't, for example, set a dimension between the top and bottom edge – because, I guess, that would require the dimension to "go back in time."

I can draw the front sketch manually before the extrusion and then use the "to vertex" extrude option, but that seems like a bit of a hack.  In particular, if the top sketch surfaces are nontrivial, I won't be able to hand draw a "poor-man's-projection."  And then the front sketch loses a lot of its ability to convey intent.  (A Use won't work here, because, again, that would require time travel.)

How is this typically handled?  The last time I used CAD seriously was something like 7 years ago – I guess it must have been AutoCAD.  Do I need to retrain myself to think differently about how models should be built?

NeilCooke

Hi @Maxpm please don’t set this answer as “rejected” because that is how a parametric modeller works (AutoCAD is an explicit modeller). How you explain it is correct and it’s neither difficult nor a hack. If you download the eBook “Mastering 3D Modeling” the inner workings of a parametric modeller are explained. You can also learn modelling best practises from the Learning Center or attend an essentials webinar. 

konstantin_shiriazdanov

Maxpm said: Do I need to retrain myself about how I think about building models?

i think if we talking about mechanical CAD the answer is YES. though if we had 3d sketches in OS some shapes (like tetrahedron and etc) would be more convinient to make directly pulling minimum convex hull on the set of 3d sketch vertices.

NeilCooke

Hi @Maxpm please don’t set this answer as “rejected” because that is how a parametric modeller works (AutoCAD is an explicit modeller). How you explain it is correct and it’s neither difficult nor a hack. If you download the eBook “Mastering 3D Modeling” the inner workings of a parametric modeller are explained. You can also learn modelling best practises from the Learning Center or attend an essentials webinar. 

brian_brady

@Maxpm you could create the sketch in the front view that contains your desired depth information first and then when you extrude go "up to vertex" and select the desired vertex from your first sketch.