how can i draw something like this?

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p3ppi
Posts: 18
Joined: Thu Dec 19, 2013 8:14 pm

how can i draw something like this?

Postby p3ppi » Thu Jan 02, 2014 2:48 pm

Hi guys I'm back in the forum,
i have a question: How can i do an elics that follows a circle or another direction that is not a line?
For example if i have to do something like the piece i let in attaches?
could somebody explain it to me?
anello.jpg
anello.jpg (14.51 KiB) Viewed 2837 times
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bejant
Posts: 6076
Joined: Thu Jul 11, 2013 3:06 pm

Re: how can i draw something like this?

Postby bejant » Thu Jan 02, 2014 4:24 pm

Hi p3ppi,

The sweep itself is not difficult, but the trick here is how to rotate the (star-shaped?) profile as it is swept around the circular path. I'm pretty sure (but not completely sure) that there's not a way to do this through the GUI.

Maybe it can be done by python code?
p3ppi
Posts: 18
Joined: Thu Dec 19, 2013 8:14 pm

Re: how can i draw something like this?

Postby p3ppi » Thu Jan 02, 2014 4:59 pm

i don't know how to use phyton, i'm a smith.
I don't know if there other programmes that do this piece, i'm thinking about autocad or varicad, but maybe neither them have this possibility. do you think that isn't it possible?
mario52
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Joined: Wed May 16, 2012 2:13 pm

Re: how can i draw something like this?

Postby mario52 » Thu Jan 02, 2014 5:16 pm

Maybe you need a special feature, go into Macros_recipes and Code_snippets, Dialog creation. My macros on Gist.github.
p3ppi
Posts: 18
Joined: Thu Dec 19, 2013 8:14 pm

Re: how can i draw something like this?

Postby p3ppi » Thu Jan 02, 2014 6:45 pm

mario52 wrote:hi
FC_twisted_bar
mario
thanks mario i'll watch it, but if it draw only straight on bar it will not be so useful i need to draw something with that profile but bended.
now i'll read!
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NormandC
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Location: Québec, Canada

Re: how can i draw something like this?

Postby NormandC » Thu Jan 02, 2014 7:15 pm

Yeah, that was a straight twisted bar, I know no way to do what you're asking in the GUI.
p3ppi
Posts: 18
Joined: Thu Dec 19, 2013 8:14 pm

Re: how can i draw something like this?

Postby p3ppi » Thu Jan 02, 2014 7:41 pm

ok, I believed that with the elics was possible draw a twisted bar, but it isn't possible. i tried.
I'm to try your system if i can understand ho to use it
jmaustpc
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Location: Australia

Re: how can i draw something like this?

Postby jmaustpc » Fri Jan 03, 2014 2:14 am

p3ppi wrote:ok, I believed that with the elics was possible draw a twisted bar, but it isn't possible. i tried.
I'm to try your system if i can understand ho to use it
You keep writing "elics" ...do you mean "Helix", as in like a 3d spiral? There is a similar word, "Ellipse" which is like a squashed circle. Is this just a translation error? :) Or do you mean something else?

I was thinking that in occ/FreeCAD a Helix is created by the C++ code placing a line on the diagonal of the surface of a cylinder (or cone for a tapered helix). to get a path like the grooves in you picture, it looks to me like you would need to do something similar but with a torus. That is lay a line diagonally on the surface of a torus or part of a torus. But I have no idea if FreeCAD/occ could be made to do such a thing.
jmaustpc
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Re: how can i draw something like this?

Postby jmaustpc » Fri Jan 03, 2014 3:17 am

I just had a thought.....and it seems to work.

make a profile for the cross section, make a few of them and rotate them around the centre of the cross section (profile) and position them round a path ...then use Part_Sweep, with multiple profiles.

Part_Placement tool in incremental mode, is very useful here.

here are some examples that might help you get started.
startwist4.fcstd
(48.55 KiB) Downloaded 89 times
in this example my profile is approximately a 4 point star. This means that you can not rotate each profile around its own centre more than 45 degrees or other wise Part_Sweep will sweep to the next point of the star around. This behaviour will vary depending on your profile. In this example you will need to place a profile at every point around the path such that the star at that point on the path has rotated no more than 45 degrees. My example has only a quarter of the path you will require (use a circle in the sketch where I used an arc). I have only used 2 profiles 90 degrees around the path from each other and the second profile is rotated 45 degrees around its centre (as well as 90 degrees around the path).

Jim
jmaustpc
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Location: Australia

Re: how can i draw something like this?

Postby jmaustpc » Fri Jan 03, 2014 4:37 am

This one is still not perfect. The last section is not what I wanted. If the path had stopped at the last profile, rather than been a complete circle, then it would have been what you wanted with a space to put the hinge of the knocker.
startwist6.fcstd
(239.76 KiB) Downloaded 81 times
I spaced the profiles at 30 degrees of rotation both on the path and around the profile centre, so that I could control the direction of the rotation of the sweep between rotated profiles, thus controlling which point of the star will sweep to which point of the next star.