Doug: Normally I can't share customer specific models, but this example is very generic and only is the very start of the model.
Hopefully the file will come across.
What I am trying to do is hold the hinge curves (see 1st picture in my post) and have at least 5 degrees draft where each side meets the parting lock.
Cool. I'm pretty busy at the moment, but I love geometry challenges like this. I'll try to take a look soon.
Here are 3 options that each produce exactly 5 degrees on each side of the P/L. None maintain the exact top & bottom profile because I don't think it is possible given the geometry. The closest, I believe, is matchdraft_5-exact_2.prt.
Hope they help.
Sorry but for some reason I can't retrieve your files. I get the below message.
I appreciate you checking into this.
Without seeing your models, the truth does appear that you can't hold top and bottom while matching at the parting line and guaranteeing 5 degree minimum draft. There may be times when going to the largest extent at the parting split and just doing a simple 5 degree draft back in both directions would be allowable. I chose the route that takes longer, but does meet the requirements.that I'm looking for.
I would love to see the software have a true match draft command.
What version of Creo are you using? I assumed Creo 4, so that's what I used. I knew I couldn't open it in Creo 2, I guess I should have tried Creo 3. Sorry about that.
The technique I used was this:
Draft the new upper surfaces at 5 degrees using the intersection curve as the draft hinge.
The bottom is exactly the same size, the top is slightly different. I hope that helps.
The only thing that doesn't work with your method is that the top draft has a small region on the right side that would undercut. I do like your method. It would be simpler than my work around. It is good to have someone look at alternative solutions.
If only true match draft were an option with Creo. It almost pulls it off with their dependent draft option. If you choose the bottom hinge as dominant you can match the hinge from the top side. Only thing is that in the same area as your method undercuts the dependent draft ends up too small.
The only thing that doesn't work with your method is that the top draft has a small region on the right side that would undercut. ...
Where are you thinking? I don't think there are any undercuts. A draft analysis shows a nice clean split:
(I used 4.9 degrees for the analysis because, for some reason, Creo will show that the draft isn't quite adequate at 5.0 degrees, even though the draft features are explicitly defined as 5.0 degrees to the TOP plane.)
Now, the top is smaller than the bottom and that upper rear edge is no longer parallel to the RIGHT plane, but it's 5 degrees everywhere, despite what Creo believes. 😄
I am speaking of the upper rear ridge. Your results would sit slightly inside mine in that area.
If the width was not critical to the customer in that area your idea would work.
I am starting out with a rectangular box prior to the draft that gets applied. My intention is to have a perfect match to the edge I've shown in the 1st picture as the draft hinge. I don't want to use up any of my tolerance inside or outside of the draft hinge. That beginning rectangle is the size we are being held to.
I would do similar, except that since if I recall the degree(s) of draft is more important on the shorter side of the parting line, I'd draft the top part 5deg, then do an "intersect" curve where the parting surface is to get the parting line. Then I'd simply sweep a cut using the intersect and bottom edges at trajectories, making sure the section is normal to a plane parallel to the bottom.