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Overview: Use extracted sketch curves to tie your sketch to previous sketches, edges or curves. Extracted curves
are associative to the parent geometry. You do not need to add any dimensional or geometric constraint to extracted curves. Extracting
geometry lets you reduce clutter in your Graphics window by making the parent geometry invisible.
Extracting Sketch Curves
Instead of recreating curves from a previous sketch, use Project 3D Elements to extract the curve into your current sketch. You can
use constraints to tie the current sketch to older sketch geometry but that requires more steps. At times, you will find that it is
impossible to tie curves to an older sketch and that you must extract the curves or points.
In the following example, the first sketch is used to create a cutout in a non-planar surface. You need to create ribs around the
cutout, but the top face of the ribs must be on a plane.
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Create a plane where you want the top face of the rib to start. Create a sketch on this plane. You can then project any of the sketch curves
you need for the current sketch.
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You can create other curves in the sketch to complete the profile.
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The value of projecting the curves is revealed when revising the model. If you change the cutout outline or position, the ribs automatically
follow along.
Extracting From Edges
Often you want to use an edge in your sketch to either reference or be part of the profile. The same principle applies with edges as
with sketches. You may just want to extract the edges instead of constraining to them. It may be that the edges are out of the sketch plane
and you need to extract them. The edge you want to extract may be a spline instead of a line or arc. To reproduce that curve in a sketch
would be difficult and time consuming.
In the following example, you need to project the edges of the cutouts to create another cutout between them.
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We created a sketch on a plane parallel to the bottom of the solid. The new cutout must be parallel to the upper edges of the cutouts. We
project the fillet edges of the cutouts. After extracting these curves, we create more curves to finish the profile.
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Creating a pad from the sketch makes the edges meet the previous cutouts.
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