How to re-use sketches in different bodies or parts?

[MrSurly]

The end goal

Design for a simple frame made from steel tubing.

What I want to do

• Have a single sketch that defines the tubing profile. This would be in a "library" body of sorts that could have other sketches.
• Have a clone (that tracks changes in the original) of that sketch in different parts or bodies.
• Offset (translate) that sketch based on another sketch.

Example

Let's say I want to design a steel table frame; let's ignore the tabletop for now, and just do the frame. Simplest form for a 4-legged table is 4 tubes for the top, making a rectangle, and then 4 tubes coming downwards from the corners for the legs.

Only thing is, I'm not sure if I'm going to use 1x1 tubes, or 1x2, etc. I create a sketch defining the profile of the tube.

For the legs, I then want to have linked copies (clones) of that sketch that are translated to the 4 corners. I would want a separate sketch that defines the dimensions that would be used to set the location of the 4 clones sketches, by maybe having a point be concurrent in each sketch.

For the top bars, something similar, although obviously the bars have to be in an orthogonal plane to the legs.

Ideally, if I need to refine the tube dimensions, I can change that single first sketch, and it would update everything else.

What I've tried

• Sketch carbon copy. Despite what the documentation says, I cannot do this across parts/bodies.
• Draft clone. I can't see how to set the clone translation location based on a sketch.
• Several other things from Google searches trying to accomplish this, that ultimately didn't really work.

FreeCAD version:

OS: Ubuntu 20.10 (ubuntu:GNOME/ubuntu)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.24276 (Git) AppImage
Build type: Release
Branch: (HEAD detached at 0.19.1)
Hash: a88db11e0a908f6e38f92bfc5187b13ebe470438
Python version: 3.8.8
Qt version: 5.12.9
Coin version: 4.0.0
OCC version: 7.4.0
Locale: English/United States (en_US)

[chrisb]

Hi and welcome to the forum!

Sketch carbon copy. Despite what the documentation says, I cannot do this across parts/bodies.
Draft clone. I can't see how to set the clone translation location based on a sketch.
Several other things from Google searches trying to accomplish this, that ultimately didn't really work.

CarbonCopy follows only the change in dimensions, not in structure. Why didn't it work for you?
Clones can be moved by changing their Placement or Attachment or Attachment Offset.

[Bance]

Have a look at this video:-

https://www.youtube.com/watch?v=1qszeRDmpvg

There are more by the same provider, who is incidently a forum member.

Also DODO WB:-

https://www.youtube.com/watch?v=oh0OG81R8Kw

[thomas-neemann]

I could show you a completely different way with arch. are you interested?

[MrSurly]

Hi and welcome to the forum!

Sketch carbon copy. Despite what the documentation says, I cannot do this across parts/bodies.
Draft clone. I can't see how to set the clone translation location based on a sketch.
Several other things from Google searches trying to accomplish this, that ultimately didn't really work.

CarbonCopy follows only the change in dimensions, not in structure. Why didn't it work for you?
Clones can be moved by changing their Placement or Attachment or Attachment Offset.

By "didn't work," I mean it simply does the error beep and doesn't do it. I'm guessing because they're not in the same body / part.

[Vincent B]

How to re-use sketches in different bodies or parts?
It's easy: make a first sketch outside any body then make a clone or binder to use it for external geometry.
(first sketch must be hiden)

[MrSurly]

Have a look at this video:-

https://www.youtube.com/watch?v=1qszeRDmpvg

There are more by the same provider, who is incidently a forum member.

Also DODO WB:-

https://www.youtube.com/watch?v=oh0OG81R8Kw

Watched both of these, but it doesn't really cover what I'm trying to do parametrically with sketches.

[MrSurly]

How to re-use sketches in different bodies or parts?
It's easy: make a first sketch outside any body then make a clone or binder to use it for external geometry.
(first sketch must be hiden)

I've tried this, but how would I then use a sketch to position it?

[MrSurly]

I could show you a completely different way with arch. are you interested?

Absolutely.

[Vincent B]

How to re-use sketches in different bodies or parts?
It's easy: make a first sketch outside any body then make a clone or binder to use it for external geometry.
(first sketch must be hiden)

I've tried this, but how would I then use a sketch to position it?

may be with datumline and datumplane?