Is loft the right tool for this?

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mconsidine
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Joined: Wed Jan 18, 2023 10:41 pm
Location: Randolph, VT USA

Is loft the right tool for this?

Post by mconsidine »

Hi,
I am using FreeCAD 0.21 (also have Link Daily version installed, if needed) on Linux Mint (Ubuntu) 21. The relevant FC file is attached and here are screenshots of the parts and the issue:
Screenshot from 2023-01-24 11-03-12.png
Screenshot from 2023-01-24 11-03-12.png (5.48 KiB) Viewed 687 times
Screenshot from 2023-01-24 10-47-28.png
Screenshot from 2023-01-24 10-47-28.png (14.15 KiB) Viewed 687 times
What I am trying to do is smoothly join the corners of the rectangles so that I have four surfaces defined. I had thought the PartDesign -> Loft tool would get me what I want, but as you can see, there is interpolation between points that I don't want.

In OpenSCAD I had been able to accomplish this by creating paths and using a spline/bezier type tool. But it was clunky and I'd like to accomplish the same thing in FC.

I tried playing around with the Curves and Surface workbenches, as well as looked through other downloadable macros/workbenches. But I don't seem to be finding the right tool or workflow.

Can anyone point out how to accomplish this? Ultimately, I am trying to create a piece that looks like this
unnamed.png
unnamed.png (33.27 KiB) Viewed 687 times
Thanks in advance for any help.
mconsidine
Attachments
a_test.FCStd
(23.07 KiB) Downloaded 17 times
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Chris_G
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Re: Is loft the right tool for this?

Post by Chris_G »

When using the Part->Loft tool, you can decrease the Max Degree to 2 to reduce oscillation.
jfc4120
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Re: Is loft the right tool for this?

Post by jfc4120 »

Try doing one section at a time.
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hammax
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Re: Is loft the right tool for this?

Post by hammax »

... Loft in another way:

a_test.PNG
a_test.PNG (30.31 KiB) Viewed 625 times
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a_test_2.FCStd
(60.51 KiB) Downloaded 11 times
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papyblaise
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Re: Is loft the right tool for this?

Post by papyblaise »

uses the intersection of 2 profiles
Attachments
pied de meule.FCStd
(264.52 KiB) Downloaded 14 times
pied de meule.JPG
pied de meule.JPG (18.29 KiB) Viewed 581 times
mconsidine
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Re: Is loft the right tool for this?

Post by mconsidine »

@hammax: Wow, elegant. Thank you for posting all that. Can you point me to how you got the profile for "Sketch009" or "Sketch010" from the segments? I get that you then used Part_Extrude on each and then Part_Common to get half the pier. And then basically mirrored that for the other half.

I infer you set up two new sketches, one in the XZ plane and the other in the YZ plane and then {here's the magic I don't about}, with the result being two profiles that were constrained to the edges of the sections and connected via a spline???

Thank you again for the help,
mconsidine
mconsidine
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Location: Randolph, VT USA

Re: Is loft the right tool for this?

Post by mconsidine »

@papyblaise :Thank you as well. You went further than I did by adding the plates and holes. I might need to come back to you on that as well :)
Thanks again,
mconsidine
chrisb
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Re: Is loft the right tool for this?

Post by chrisb »

I have here used a B-spline with 3 control points, which makes it very smooth. I used the brand new possibility of 0.21 in Sketcher to use point-on-object constraints on a B-spline.
It doesn't quite meet all the intermediate sections, though. If that is a requirement, you woul need a B-Spline with more control points. It could be completed "à la papyblaise".
SnipScreenshot-aa89ed.png
SnipScreenshot-aa89ed.png (16.34 KiB) Viewed 402 times
Attachments
tower_cb.FCStd
(15.29 KiB) Downloaded 13 times
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
chrisb
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Re: Is loft the right tool for this?

Post by chrisb »

I had an issue with the B-Spline on the left side, but the other side worked with a 3-control-points-Bspline surprisingly well too, see https://forum.freecadweb.org/viewtopic. ... 31#p655831.
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hammax
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Re: Is loft the right tool for this?

Post by hammax »

... I only used 4-Control_Point BSplines with adapted weight radius
snapped to external references on bottom and top - rest by eye.

a_test_3.PNG
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Attachments
a_test_3.FCStd
FC.20.1
(59.4 KiB) Downloaded 9 times
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