Subtractive loft issue

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bitskrieg
Posts: 5
Joined: Fri Jul 23, 2021 5:22 pm

Subtractive loft issue

Post by bitskrieg »

Hi all,

I'm modeling dovetail-like joinery and after messing around with objects created in part design workbench and then fusing them with the functions in the part workbench I kind of realized that I was making my life more difficult than needed, so I decided to re-create all the parts using part design only (specifically the loft functionality).

Sketch of half of the subtractive loft:
freecad_forum_sketch.PNG
freecad_forum_sketch.PNG (54.39 KiB) Viewed 352 times
I suspected that there might be an issue with the drawing at (0,0) and sure enough I can't pad this sketch and get a TopoDS:Face error, presumably because that point has no actual dimensions to pad. I suspect that when I create the second sketch for the loft and then try and use the subtractive loft functionality to create the male portion of the dovetail out of a solid cube, I will have similar issues.

I know that I can break this into 4 sketches and do two subtractive lofts (one for each side, bisected at the intersection), but I'd kind of like to keep it all contained and easier to adjust dimensions if possible.

Any tips on how to make this work with just two sketches/a single loft, or do I need to break it up?

Edit: I know in this particular case just doing an additive loft with the inverse sketch would work, but the dovetail geometry needs to work on other shapes (like a cylinder) and I'm not quite good enough at freeCAD to do that yet.

Example:
freecad_forum_sketch2.PNG
freecad_forum_sketch2.PNG (66.82 KiB) Viewed 352 times
Part of what I'm trying to accomplish is completely get rid of boolean/fusing operations and just do a simple subtractive loft on any solid where I need joinery, with the two sketches changing depending on whether or not I want a male or female end - hope that makes my goals more clear.

Thanks in advance.

Version Info:

OS: Windows 10 Version 2009
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.24291 (Git)
Build type: Release
Branch: releases/FreeCAD-0-19
Hash: 7b5e18a0759de778b74d3a5c17eba9cb815035ac
Python version: 3.8.6+
Qt version: 5.15.2
Coin version: 4.0.1
OCC version: 7.5.0
Locale: English/United States (en_US)
chrisb
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Joined: Tue Mar 17, 2015 9:14 am

Re: Subtractive loft issue

Post by chrisb »

You can lift the upper line by a mm or so.
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Shalmeneser
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Re: Subtractive loft issue

Post by Shalmeneser »

Small fillet at the tip.
Attachments
Eclair.FCStd
(13.14 KiB) Downloaded 11 times
Corpus delicti 81.png
Corpus delicti 81.png (30.21 KiB) Viewed 335 times
Snip macro screenshot-e3b076.png
Snip macro screenshot-e3b076.png (10.82 KiB) Viewed 335 times
bitskrieg
Posts: 5
Joined: Fri Jul 23, 2021 5:22 pm

Re: Subtractive loft issue

Post by bitskrieg »

Both great answers that work well - thank you!
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