Drawing a sketch on a curved surface

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Mtrprks
Posts: 17
Joined: Wed Aug 08, 2018 4:11 pm

Drawing a sketch on a curved surface

Post by Mtrprks »

I am trying to design and print a ring with a 19.1 mm ID and 6.35 mm wall thickness that has four oval-shaped tongues sticking out at 90 degrees apart from one another, on the outside of the ring. One pair of the tongues are oriented parallel to the plane (z is coming through the ring hole) and the other is perpendicular. My problem is drawing on the OD of the object I have created so far. Sketch requires a planar surface. The tongue would only have to stick out by 4 mm, a long axis of 5mm, and a short axis of 3 mm. I am attaching both the CAD file and a pic of the tongue as I envision it. The idea is that the tongues would slide into grooves holding the ring in one of two orthogonal positions (perpendicular to the ground or parallel).

OS: Win7
FreeCAD ver: .17
Attachments
IMC TT Mount.FCStd
(15.32 KiB) Downloaded 22 times
Tongue.PNG
Tongue.PNG (15.97 KiB) Viewed 2550 times
chrisb
Posts: 37695
Joined: Tue Mar 17, 2015 9:14 am

Re: Drawing a sketch on a curved surface

Post by chrisb »

Hi Mtrprks, welcome to the forum.
Can you provide an image of what you try to achieve? A link to an image or an uploaded doodle would be fine.

Concerning your model: You can delete both pockets and Pad001. Then use the sketch directly for the pocket.
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TheMarkster
Posts: 2635
Joined: Thu Apr 05, 2018 1:53 am

Re: Drawing a sketch on a curved surface

Post by TheMarkster »

Like this?
imc tt mount.png
imc tt mount.png (21.59 KiB) Viewed 2527 times
Attachments
IMC TT Mount2.FCStd
(47.32 KiB) Downloaded 33 times
My FreeCAD video series on youtube: https://www.youtube.com/c/mwganson
Mtrprks
Posts: 17
Joined: Wed Aug 08, 2018 4:11 pm

Re: Drawing a sketch on a curved surface

Post by Mtrprks »

I appreciate you guys taking the time to answer. I doodled something up in paint to best convey what I am trying to get it to look like. The previous comment was close
Attachments
Perpendicular tongue side
Perpendicular tongue side
Perp tongue side view.png (22.76 KiB) Viewed 2489 times
Perpendicular tongue front
Perpendicular tongue front
Perp tongue front view.png (24.71 KiB) Viewed 2489 times
Parallel tongue side
Parallel tongue side
Para tongue side view.png (57.12 KiB) Viewed 2489 times
Parallel tongue front
Parallel tongue front
Para tongue front view.png (25.51 KiB) Viewed 2489 times
Bance
Posts: 2264
Joined: Wed Feb 11, 2015 3:00 pm
Location: London

Re: Drawing a sketch on a curved surface

Post by Bance »

One way of doing this is to make the lugs first, another would be to sketch the lugs on a std plane and use attachment offset to position them as required..

See attached.
Lugs.jpeg
Lugs.jpeg (34.06 KiB) Viewed 2466 times
HTH Steve.
LugsFirst.fcstd
(124.67 KiB) Downloaded 44 times
LugsAttachOffset.fcstd
(134.3 KiB) Downloaded 56 times
Mtrprks
Posts: 17
Joined: Wed Aug 08, 2018 4:11 pm

Re: Drawing a sketch on a curved surface

Post by Mtrprks »

Bance wrote: Sat Aug 11, 2018 8:16 am One way of doing this is to make the lugs first, another would be to sketch the lugs on a std plane and use attachment offset to position them as required..

See attached.

Lugs.jpeg

HTH Steve.

LugsFirst.fcstd

LugsAttachOffset.fcstd
Thank you very much for your help.
Mtrprks
Posts: 17
Joined: Wed Aug 08, 2018 4:11 pm

Re: Drawing a sketch on a curved surface

Post by Mtrprks »

As an update to the gizmo (there is a word I have not used in a while, I'll now refer to all designs-in-progress as gizmos), thanks to everyone's help, I have it looking and dimensioned just how I want it and I'm ready to generate an STL file. Now when I originally pieced this together, I started with a new design in the "Part Design" workbench and created it with four separate "Parts", a padded cylinder with a circular pocket for the central piece, four parts for the lugs, and switched to "Part" workbench to fashion a cylinder that would give me the hole in the ring (for a set screw). When it came time to export an STL i was trying to decide how best to do so. I thought I should combine them into a single entity and then export. Combing them was a curious process because depending how I did it, seemed to leave various artifacts behind. For example: trying to Boolean combine individual parts caused the "Cut" to not appear and other weird figments. Eventually I arrived at the successful output (I think?) shown in "....Mount 5". "...Mount 3" is the original form.

My questions are these: Did I use the most effective means in designing this object? Did I use the best way in combining the parts? I feel there are many, many ways to skin this cat but I'd like to hear from the more experienced users on their advice. I also feel I am causing much of my own confusions misunderstanding the hierarchy and dependency of the project tree

Thanks!
Attachments
Project Tree
Project Tree
tree.PNG (38.8 KiB) Viewed 2373 times
Gizmo
Gizmo
gizmo.png (89.85 KiB) Viewed 2373 times
Bance
Posts: 2264
Joined: Wed Feb 11, 2015 3:00 pm
Location: London

Re: Drawing a sketch on a curved surface

Post by Bance »

As a rule when designing in PD workbench it's best to stay there.

You could quite easily have used a subtractive feature to create the set screw hole, or a sketch on a datum plane, or a sketch on a std plane with appropriate positioning. This keeps the History tree nice and clean, and provides a single active(visible) body for export.

See enclosed.

There will be other views I'm sure someone else will chip in!

HTH Steve.
LugsAttachOffset.fcstd
(194.78 KiB) Downloaded 52 times
Bance
Posts: 2264
Joined: Wed Feb 11, 2015 3:00 pm
Location: London

Re: Drawing a sketch on a curved surface

Post by Bance »

Part design bodies are meant to be single contiguous solids, such as are printed by 3D printers.

There is no need to create a separate body for each feature of the object, unless it is to be fabricated separately.

So designing a wooden chair for example would require separate bodies for each piece, because they are made singularly and joined to form the whole. Whereas a casting mold would be a single object in a single body. Does that make sense?

Steve.
Mtrprks
Posts: 17
Joined: Wed Aug 08, 2018 4:11 pm

Re: Drawing a sketch on a curved surface

Post by Mtrprks »

Thanks for your time in clarifying for me. It helped very much!
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