How to model a parametric hook?

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Christoph
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Joined: Fri Jul 08, 2016 9:02 pm

How to model a parametric hook?

Postby Christoph » Sun Apr 15, 2018 1:10 pm

Hi,

maybe two years ago I tried to model a smooth looking parametric hook, but failed pretty much (because I couldn't find a way to place sketches on the right places). Now using Part Design next, the job can be done within 15 minutes. I like the new Part Design! The new tools like Datum Planes are a huge step forward for FreeCAD.

If you want to see how I designed the hook, follow the link to youtube (be aware, the video is in german):

Edit: I recorded the video again and tried to use your advices. Many thanks to you, I never ever saw a forum which is as helpful than this one!

phpBB [video]
Last edited by Christoph on Sat Apr 21, 2018 1:32 pm, edited 1 time in total.
chrisb
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Re: How to model a parametric hook?

Postby chrisb » Sun Apr 15, 2018 1:32 pm

Nice video. In the first three minutes you don't need the construction lines. In 0.17 you can apply horizontal constraints directly to points. A serious problem can be the symmetry constraint. It might work - as it apparently does here - but it often leads to problems. Your Sketch is overconstrained because the symmetry implies the horizontal constraint.
More later, I'm short of time now.
You need at least FreeCAD 0.19.23300 to edit my current sketches.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
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Kunda1
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Re: How to model a parametric hook?

Postby Kunda1 » Sun Apr 15, 2018 3:47 pm

Christoph wrote:
Sun Apr 15, 2018 1:10 pm
Heads up: You can use the [video] tags to display videos
Nice job, btw.
Alone you go faster. Together we go farther
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chrisb
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Re: How to model a parametric hook?

Postby chrisb » Sun Apr 15, 2018 4:08 pm

I have seen the rest and I am pleased by the usage of the datum planes as sections. I hope we will see more of your videos!
A final remark: The first datum plane is in fact the XY plane so you could omit it without any loss.
You need at least FreeCAD 0.19.23300 to edit my current sketches.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
tommeyers
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Re: How to model a parametric hook?

Postby tommeyers » Sun Apr 15, 2018 7:11 pm

Christoph, Thanks for this tutorial. It came at the right time for me - a relatively new user. It am starting to put some of my jewelry designs in FreeCAD and will need to use those techniques. Tom Meyers
freecad-heini-1
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Re: How to model a parametric hook?

Postby freecad-heini-1 » Sun Apr 15, 2018 7:30 pm

Hi Christoph,
thank you very much, that is a nice video tutorial.

Please read this trick to avoid the many segments of the sweep-surface:
https://forum.freecadweb.org/viewtopic. ... 73#p180473

Concerning fillets, it's not needed to select so many edges if it's a tangent curve, one edge will do the job.
https://forum.freecadweb.org/viewtopic. ... 19#p198819

The helper sketcher lines are not needed, because there is another method to create the datum planes, please check my animation:
datum_plane_normal_zur_kante.gif
datum_plane_normal_zur_kante.gif (888.78 KiB) Viewed 1894 times
Please have a look at the zebra-tool inside the curves- and nurbs-workbench:
https://forum.freecadweb.org/viewtopic. ... 87#p204587

Best regards

Wilfried
Christoph
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Re: How to model a parametric hook?

Postby Christoph » Mon Apr 16, 2018 6:46 pm

Hi,

thank you all for your feedback! Today I tried your advices, and the workflow is now much faster. Especially the orientation of the Datum Planes as advices from Wilfried lift the process up to a higher level. Only the conversion of the sweep sketch into a b-spline didn't work out, the sketch get always broken. Wilfried, do you have a solution for that?

I attach the file with the broken sweep sketch.

To avoid spreading working methods which are not ideal, I decided to record the video again (probably next weekend).

Regards
Christoph

OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.13532 (Git)
Build type: Release
Branch: master
Hash: 4adeb7702da610da2c7f3014217044167109f0d6
Python version: 2.7.14
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 7.2.0
Locale: German/Germany (de_DE)
Attachments
Hook_sketch_broken.FCStd
(22.14 KiB) Downloaded 43 times
convert into bspline.JPG
convert into bspline.JPG (126.91 KiB) Viewed 1822 times
freecad-heini-1
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Re: How to model a parametric hook?

Postby freecad-heini-1 » Tue Apr 17, 2018 7:27 am

Christoph wrote:
Mon Apr 16, 2018 6:46 pm
Hi,

thank you all for your feedback! Today I tried your advices, and the workflow is now much faster. Especially the orientation of the Datum Planes as advices from Wilfried lift the process up to a higher level. Only the conversion of the sweep sketch into a b-spline didn't work out, the sketch get always broken. Wilfried, do you have a solution for
I'm glad that I could help you with the datum-planes.
Concerning the "convert given geometry to b-spline" tool, for me it seems that this tool is broken / has a bug.
I remember some cases with that tool in past, it worked like a charme.

But there is another great tool inside the curves workbench. It can convert a bunch of curves into one bspline curve.
Please let me show you a short demo:
join_curve_corner-break.gif
join_curve_corner-break.gif (840.68 KiB) Viewed 1794 times
Please care about the data-tab, there is an option "corner-break", change into false.
Please try this trick on the crane hook for the sweep-profiles, and you will see a great result with a smooth surface.

Best regards
Wilfried
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Re: How to model a parametric hook?

Postby freecad-heini-1 » Tue Apr 17, 2018 9:05 am

Christoph wrote:
Mon Apr 16, 2018 6:46 pm
@Christoph, please upload your freecad-file.
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Re: How to model a parametric hook?

Postby freecad-heini-1 » Tue Apr 17, 2018 3:37 pm

Here you can see the difference.

1. conventional sweep:
conventional_sweep.png
conventional_sweep.png (82.77 KiB) Viewed 1740 times
fc017_sweep_normal.fcstd
(129.36 KiB) Downloaded 55 times
2. smooth sweep:
fc017_sweep_smooth.fcstd
(58.14 KiB) Downloaded 55 times
smoothl_sweep.png
smoothl_sweep.png (75.78 KiB) Viewed 1740 times