Attaching sketch to face

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chris s
Posts: 17
Joined: Mon Mar 06, 2017 1:23 pm

Attaching sketch to face

Postby chris s » Mon Feb 26, 2018 7:08 pm

I want to pick up on the end face of a swept object and sweep it with a new path. But the end of the object is not a sketch so how can I convert it to a sketch? Or, I can generate a new sketch to copy the face but I cant find a way of picking up on the existing points.

I hope I made that clear.
chrisb
Posts: 19604
Joined: Tue Mar 17, 2015 9:14 am

Re: Attaching sketch to face

Postby chrisb » Mon Feb 26, 2018 7:17 pm

chris s wrote:
Mon Feb 26, 2018 7:08 pm
I hope I made that clear.
Sort of. You should tell us which FreeCAD version you use, because the answer may depend on it. Follow the "IMORTANT:..." link at the top of the page and find out how. If it is not too big you can upload your file and we can have a look at the concrete situation.
chris s
Posts: 17
Joined: Mon Mar 06, 2017 1:23 pm

Re: Attaching sketch to face

Postby chris s » Mon Feb 26, 2018 8:16 pm

0.16 Rev 6712. File attached.
Attachments
Catch jack screw.FCStd
(16.03 KiB) Downloaded 11 times
triplus
Posts: 8796
Joined: Mon Dec 12, 2011 4:45 pm

Re: Attaching sketch to face

Postby triplus » Mon Feb 26, 2018 8:32 pm

Hi @chris s

In general you can use Sketcher External command to get the points of the geometry you have attached the sketch on.
chrisb
Posts: 19604
Joined: Tue Mar 17, 2015 9:14 am

Re: Attaching sketch to face

Postby chrisb » Mon Feb 26, 2018 9:40 pm

triplus wrote:
Mon Feb 26, 2018 8:32 pm
In general you can use Sketcher External command to get the points of the geometry you have attached the sketch on.
Beware: unlike the results of pads and pockets you cannot select the edges as external geometry, only the vertices, as triplus has pointed(!) out.
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Mongrel_Shark
Posts: 132
Joined: Sat Oct 15, 2016 9:54 am
Location: Australia

Re: Attaching sketch to face

Postby Mongrel_Shark » Tue Feb 27, 2018 12:41 am

I have 2 ways I would aproach this.

Fist is quick and dirty. Use the external geometry tool to select all the external edges, then attach a sketch to that and pad/sweep.

This will give you problems if you make certain changes earlier in the tree as occ will re-number all the edges and it will become an invalid sketch. So not very parametric.


Second way is to copy the first sketch from the other end of your sweep. By selecting in tree then ctrl+c. Then paste copy (and place in appropriate body if in 0.17) then attach to face. By selecting the face and pressing the attach sketch to face button then selecting your sketch from the drop down.
chris s
Posts: 17
Joined: Mon Mar 06, 2017 1:23 pm

Re: Attaching sketch to face

Postby chris s » Tue Feb 27, 2018 6:05 pm

Thanks guys, Sketcher External works a treat. Selected the vertices and placed my sketch onto them. Then used Revolve to add my extra part and then fused them. Made a double helix by copying and rotating. This will be a cutout inside a tube to form an internal jacking thread that works over approx 180 deg. The top rotated section will be the landing for the screw. Crazy eh?
Attachments
Catch jack screw2.FCStd
(28.3 KiB) Downloaded 11 times
triplus
Posts: 8796
Joined: Mon Dec 12, 2011 4:45 pm

Re: Attaching sketch to face

Postby triplus » Wed Feb 28, 2018 6:39 pm

Mongrel_Shark wrote:
Tue Feb 27, 2018 12:41 am
I have 2 ways I would aproach this.

Fist is quick and dirty. Use the external geometry tool to select all the external edges, then attach a sketch to that and pad/sweep.

This will give you problems if you make certain changes earlier in the tree as occ will re-number all the edges and it will become an invalid sketch. So not very parametric.


Second way is to copy the first sketch from the other end of your sweep. By selecting in tree then ctrl+c. Then paste copy (and place in appropriate body if in 0.17) then attach to face. By selecting the face and pressing the attach sketch to face button then selecting your sketch from the drop down.
And what will happen in the second approach if you go back and add or remove geometry? Things like sketch getting attached to a different face? And in addition this approach is not parametric at all? Unless you would bother with adding expression between sketches. And if you do that and go back to add or remove geometry ... ;) As for your second suggestion. Draft Facebinder (FreeCAD 0.16) or using the face directly in PartDesign workbench (FreeCAD 0.17) is another available option.
chris s wrote:
Tue Feb 27, 2018 6:05 pm
Thanks guys, Sketcher External works a treat.
Good to hear that.
The top rotated section will be the landing for the screw. Crazy eh?
Nah. :)