Attaching sketch to face

[chris s]

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]

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]

0.16 Rev 6712. File attached.

[triplus]

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]

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.

[Mongrel_Shark]

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]

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?

[triplus]

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.

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.