Extrusion Using 2 Orthogonal Sketches

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omri
Posts: 3
Joined: Sun Jan 20, 2019 7:54 pm

Extrusion Using 2 Orthogonal Sketches

Postby omri » Sun Jan 20, 2019 8:29 pm

Hey All,
So I've been using FreeCAD (and CAD in general) now for about a month or so designing mounts and such for 3D printing. I have a reasonable amount of 3D modeling experience in Blender but am absolutely loving parametric modeling where you can simply change your mind on the length/dimension of something after the fact and just change it and the whole 2D sketch and 3D model adjust accordingly.
One problem I'm having is this concept seems to only apply to 2D and not 3D since sketches are 2D. What I mean by that is I create my sketch in 2D, fully constrained with dimensions but than I have to extrude it to bring it into 3D. When I extrude it, I have to specify the forward and backward extrusion length and possibly move/translate the 3D extrusion along the extrusion axis. For these extrusion lengths, I have to figure out the numbers in my head with additions and subtractions. Worse, since most parts I'm making are boolean unions of multiple 3D extrusions that butt up against one another, If I do decide to change one of them at some point, I have to change the extrusion lengths and possibly the translations of any of the neighboring/butted up against parts. This seems to me a big gaping hole, a pain and against the spirit of parametric modeling.
What would be absolutely awesome is you could make a 3D extrusion using 2 sketches on separate planes (probably 2 orthogonal planes) without specifying forward/backward extrusion lengths or a movement/translation across the extrusion axis at all. You're effectively extruding using a planform and a profile sketch. The idea would be to select these 2 2D sketches on different planes, click the "dual sketch extrusion" button and you get your 3D extrusion. Technically, what this button would do is extrude both sketches into infinity in both directions and take the boolean intersection of them. Right now to accomplish this, I have to manually extrude both sketches using some large extrusion lengths (as an approximation for infinite extrusion) and manually do a boolean intersection.
Is there some way to already accomplish this that I'm unaware of? Should I make a feature request of this? Is there some other way to do extrusion with specifying hardcoded extrusion lengths and hardcoded translation/move lengths? See the attached screenshots and file to see what I mean.

Thanks!!!
Profile.jpg
Profile.jpg (168.23 KiB) Viewed 134 times
Planform.jpg
Planform.jpg (173.28 KiB) Viewed 134 times
3D.jpg
3D.jpg (109.86 KiB) Viewed 134 times
Attachments
Planform And Profile Extrusion.FCStd
(11.46 KiB) Downloaded 1 time
GeneFC
Posts: 1000
Joined: Sat Mar 19, 2016 3:36 pm
Location: Punta Gorda, FL

Re: Extrusion Using 2 Orthogonal Sketches

Postby GeneFC » Sun Jan 20, 2019 9:30 pm

Not sure what your end goal is beyond this very basic model, but it seems that an assembly operation might work for you. Assembly 2+ has matured quite nicely, and can be easily added to your FreeCAD installation through the Tools >> Addon Manager menu item.
chrisb
Posts: 14572
Joined: Tue Mar 17, 2015 9:14 am

Re: Extrusion Using 2 Orthogonal Sketches

Postby chrisb » Sun Jan 20, 2019 10:05 pm

There is a technique which was referred to as "Wilfried's trick": https://forum.freecadweb.org/viewtopic. ... 45#p165745. It's in german, but images and video should be understandable.
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NormandC
Posts: 18474
Joined: Sat Feb 06, 2010 9:52 pm
Location: Québec, Canada

Re: Extrusion Using 2 Orthogonal Sketches

Postby NormandC » Mon Jan 21, 2019 12:21 am

Hello omri,

Welcome here.

omri wrote:
Sun Jan 20, 2019 8:29 pm
When I extrude it, I have to specify the forward and backward extrusion length and possibly move/translate the 3D extrusion along the extrusion axis. For these extrusion lengths, I have to figure out the numbers in my head with additions and subtractions. Worse, since most parts I'm making are boolean unions of multiple 3D extrusions that butt up against one another, If I do decide to change one of them at some point, I have to change the extrusion lengths and possibly the translations of any of the neighboring/butted up against parts. This seems to me a big gaping hole, a pain and against the spirit of parametric modeling.
Would you have a file for us showing this work flow? There may be a method, using the PartDesign workbench rather than the Part workbench.

In PartDesign, you can reference outside bodies with Shapebinders, maybe that could do what you're looking for. Placement of bodies in reference to each other may be a little more involved though.

Truth is, what you are asking for is modelling in context of an assembly. FreeCAD does not support this yet, it doesn't even have a native assembly module. I believe realthunder has done some work in this regard with his Assembly3 add-on, but it requires a complete fork of FreeCAD.