[Tip] FreeCAD does square helices!

[NormandC]

How cool is that, uh?

FC_square_spring_01.png (124.47 KiB) Viewed 6822 times

On the French forum someone asked how to make such a square spring. I'll admit I hadn't the slightest idea how it could be done so I googled it and I found this tutorial for SolidWorks. http://freelancecaddesign.com/wordpress/?p=154

After a little bit of experimenting I was able to duplicate the SW process in FreeCAD. I never thought to use the Part Section tool in such a manner before.

One thing though, it's not very robust. I started with a 10 revolution spring then 6 and the end sweep was messed up with missing sections. Don't set the Frenet setting to true! And even though the Section creates a single object, you need to select all the individual segments for the sweep path. So in the end I decided to make a single turn and make a Draft Array after that.

The file is too big to attach, I uploaded it to my Google Drive.
Square_Helix.fcstd (15MB)
2022-10-18: this old, obsolete file is no longer available. I have created a newer model, the filesize is much smaller (a mere 190KB), and attached it to this reply: https://forum.freecad.org/viewtopic.php ... 85#p634034

[quick61]

Wow Norm, it took me a few moments to figure out just what you did there, but only a few. Very slick. I don't think I have ever "used" the section tool, and only played with it for a minute or two at most. I'll have to start to think of that tool more now that I'v seen this. Thanks for sharing. Very educational, at least for me it was.

Mark

Edit - OK, think I have it all figured out now. One can do Triangular springs too.

Triangular_Spring.png (90.25 KiB) Viewed 6806 times

[yorik]

Hmm quite intelligent technique... But are the straight segments totally straight? My instinct would say that the intersection of the helix with the cube would produce slightly curved lines...

[jmaustpc]

that's really interesting Norm...

Some other things you can do with a Part Helix that might not be totally obvious
1) create a default Part Helix....Part Extrude the Helix, change the default extrude from z=1 to less e.g. z=0.5 ...you will get a helical face in the z direction, i.e. like a face stripped from a cylindrical face
2)you can create to helices with a different diameter, then loft from on helix to the other and get the same sort of face as Norm did by sweeping a line along a Helix.
3)once you have either of the above you can then apply a Part Offset to that face and either have two faces or tick "fill" and make a rectangular section helix.

funwithhelix.jpg (62.29 KiB) Viewed 6748 times

Here is the above fcstd file

funwithahelixortwo.fcstd

(19.3 KiB) Downloaded 180 times

Jim

[bejant]

The thought never occurred to use booleans so as to create a path; that's a tip I'll have to keep in mind.

[NormandC]

But are the straight segments totally straight? My instinct would say that the intersection of the helix with the cube would produce slightly curved lines...

You're probably right.

Interesting uses, Jim. I'm so used for extrude to be only used on planar sketches in other CAD software that I forget FreeCAD's Part Extrude can work on almost any shape.

The thought never occurred to use booleans so as to create a path;

I didn't use a boolean, but the Part Section tool. I tried a boolean Intersect and didn't get what I'd expect.

[jmaustpc]

booleans will not be reliable between different types of shapes, e.g a boolean between a face and a solid is not likely to work.

[quick61]

Hmm quite intelligent technique... But are the straight segments totally straight? My instinct would say that the intersection of the helix with the cube would produce slightly curved lines...

I think you are kind of correct Yorik, it looks like there is a very slight "wave" in the segments, not just a simple curve. Hard to detect until you produce a large enough segment and connect a Draft line with the segment ends and zoom in, but it's there. One time I did get some bends, or more like "kinks" in the straight segments when I swept the helix. A result of something not quite right with the Frenet function I would guess.

Lofting between 2 helixs of the same pitch / height produced no such problem with the kinks in any of the experimenting I have done so far. IMO the lofting technique seems to be more accurate than the sweep is in producing the section/path. Though both have that slight wave in the segments.

Mark

[wmayer]

And even though the Section creates a single object, you need to select all the individual segments for the sweep path.

Now it's possible to just select again the selected edge. If the part is an edge or wire or a compound of them it will be completely selected.

[NormandC]

Thanks Werner!