What I from time to time need is to be able to draft 2 sides dependently but carry at least the minimum draft value to both sides. The problem is that many times the thickness from the depth from the parting line along a part might favor the top side as well as favoring the bottom side.
There is a hinge in both the top and bottom, and the draft has to be additive.
If you draft each side independently there will be an overbite noticeable.
If you look near the red lines you can see that by drafting independently the overbite is on the bottom impression in the above picture.
Looking to the next picture however you can see in the red circled region that the overbite is on the top side.
What I need to do is match draft to where a minimum value of 5 degrees is held on both sides.
If I draft these sides dependently I could either favor the middle picture side or the bottom picture side. The problem is that one side will be exactly 5 degrees while the other will have a region or regions less than 5 degrees.
In our line of work we have to have a minimum of 5 degree draft in order to achieve separation from the dies.
If there is no solution for this I imagine that I could draft both sides 5 degrees, build a sketch with the outermost draft extent from each side taken to the parting lock split. Then I would need to generate an intersection to the parting face with that sketch. After this I could build a swept blend or independent ruled surfaces that join at the parting lock.
This certainly is possible but a lot of extra work.
The way you are doing it the top and bottom of the part remain the same size and the center is growing with the draft. What about creating a curve at the parting line intersection and using that curve as the draft hinge so that the top and bottom get smaller with the draft? Then you could use a single draft feature, split at draft hinge, dependently at 5 degrees.
Draft one side, the one that makes sense, then sweep a cut around the other curve with the section normal to a plane parallel to the surface. This will give you a parting line wherever it ends up. If you absolutely need the parting line in a particular location, you could sweep a section adding material using the surface you have shown and the upper and lower edges as trajectories (turn on variable secion option).
Also, realize that the geometry simply may be impossible to create like you wish, you might have to adjust your design.
I have tried this type of technique but I don't believe this would work this specific application. The customer won't want the extra stock that would be incurred by drafting back the largest combined profile.
Perhaps I'm not understanding your concern, but I would think the geometry is the geometry, regardless of technique. If you require a certain minimum or maximum size and a certain minimum draft, you're going to get what you get. How you get there is immaterial, I would think.
Sometimes, geometry drives what's needed regardless of customer "wants". No getting around that and they'll have to understand that. What it seems you want is somewhat, but not too unusual, it's just that you either get the step, or you sweep a cut, or sweep a protrusion. There is no other way to get the draft you want.
Frank, I like your idea. In some cases this would work, perhaps even with the one I've shown with the snapshots. There are some reasons why we do have to cling to a specific designed parting line. I would like to try this sometime to see whether it would work as I think I understand you are describing this.
I have come up with the drafted part design with 2 boundary blends as I specified above. I had 3 sets of curves so it was fairly easy to go top to parting and from parting to bottom.
What I really would hope for would be a true match draft capability with the Creo software.
Just FYI I will show you what I end up with by combining 2 boundary blends (which were solidified out of the original shape).
In our line of work this would be a typical application of match draft. Where you hold the top and bottom lines in the die and you have to adjust draft to meet at the parting line.
Can you share the file? I might be able to play with it a bit, assuming it isn't Creo 5.