Shape binder...modeling challenge

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drmacro
Posts: 2566
Joined: Sun Mar 02, 2014 4:35 pm

Shape binder...modeling challenge

Postby drmacro » Tue Apr 21, 2020 7:36 pm

I mentioned in another thread that I hadn't figured out a good use case for shape binders. This meant it was a challenge to myself, so below I offer another exercise from "The Book".

Way back, when we were done with drawings, we'd turn them over to the "checker". Since he always used a red pencil...we referred to his handiwork as bleeding on our work. So, here ya go checkers, let the bleeding begin. :lol:

Some notes for possible future readers:

- done in Part Design
- a single body
- no references to solid's edges or faces
- only sketches used
- shape binder used for all references.

Let me know if I violated any of the notes or if you think more notes are apropos.
Fig_8-57.jpg
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Fig_8-57-1.png
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Attachments
Fig_8-57-1.FCStd
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Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."

My beginners, written treatise: Learning FreeCAD
freedman
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Location: Washington State, USA

Re: Shape binder...modeling challenge

Postby freedman » Tue Apr 21, 2020 8:12 pm

This is out of the docs "A shape binder is a reference object that links to edges or faces from another Body." If you want to learn to use shapebinders then wouldn't you want a two body challenge.
Last edited by freedman on Tue Apr 21, 2020 8:35 pm, edited 1 time in total.
kisolre
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Joined: Wed Nov 21, 2018 1:13 pm

Re: Shape binder...modeling challenge

Postby kisolre » Tue Apr 21, 2020 8:16 pm

No. This is not how you use a shape binder. There is no point using a shapebinder from the same body instead of just using the actual geometry. And since the shape(s) under the shapebinder are still referenced as edges/faces/vertices the can still go crazy if the original shape changes.
Imagine Body is a toolholder. And you need to design a tool (body001) to use with that toolholder. By using shapebinder FROM body INSIDE body001 you get a reference geometry that you can use to create your tools connecting part to the toolholder. Then using another shapebinder from the thing the tool needs to work on (another body) you create the working end of the tool.
.
Attachments
ShapeBinder.JPG
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user1234
Posts: 347
Joined: Mon Jul 11, 2016 5:08 pm

Re: Shape binder...modeling challenge

Postby user1234 » Tue Apr 21, 2020 9:31 pm

Hello!
drmacro wrote:
Tue Apr 21, 2020 7:36 pm
..... a good use case for shape binders.
In my opinion that is a bad use of shape binders. (no offensive!)

If i change the sketch only a little bit, the whole model breaks.
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Make the sketches independent from everything, except the origins or expressions. The positioning of the sketches you should make in the attachement (ok now i see, you did it) and the height of the pads/pocket or use, reverse, thought all, ...... Make simple sketches, also when they are on the same plane (easier to handle), then make more sketches on the same plane and for that you can use expression for the positioning for the same plane (i hope you know what i mean).
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(sketches are not constrained here)
kisolre wrote:
Tue Apr 21, 2020 8:16 pm
There is no point using a shapebinder from the same body instead of just using the actual geometry.
Sometimes yes and no. Here a hybrid.
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Sorry for bad english
Greetings
drmacro
Posts: 2566
Joined: Sun Mar 02, 2014 4:35 pm

Re: Shape binder...modeling challenge

Postby drmacro » Tue Apr 21, 2020 10:01 pm

Hmm..

The shape binder in my example references the original sketch. Not model edges or faces.

If I was going to make another body, as suggested for a mating tool, what would prevent the use of another shape binder.

To me the sketches I made are simple. There are no symmetries to mirror for example. What other simplifications can you see?

I tested several changes to things and nothing broke, except when I actually attempted a change that was geometrically impossible. (I will attempt more in the morning.)

In the mean time, for discussion...if the shape binder stabilizes the model, why wouldn't it be used in any way possible?
Is there a drawback?

The sketches in the model presented are attached to default planes with offsets, reverse mapping, or in one case a rotation. Is this not why attachment offsets, etc. are available options?
Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."

My beginners, written treatise: Learning FreeCAD
kisolre
Posts: 3134
Joined: Wed Nov 21, 2018 1:13 pm

Re: Shape binder...modeling challenge

Postby kisolre » Tue Apr 21, 2020 11:13 pm

user1234 wrote:
Tue Apr 21, 2020 9:31 pm
Here a hybrid.
Where?
.
Attachments
ShapebinderToOtherBody.JPG
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freedman
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Location: Washington State, USA

Re: Shape binder...modeling challenge

Postby freedman » Tue Apr 21, 2020 11:16 pm

drmacro
The model; nice work! Now you can do just about anything. Maybe you didn't need a shapebinder but now you know how to use one. I think you have succeeded in becoming a FreeCAD modeler.
kisolre
Posts: 3134
Joined: Wed Nov 21, 2018 1:13 pm

Re: Shape binder...modeling challenge

Postby kisolre » Tue Apr 21, 2020 11:20 pm

drmacro wrote:
Tue Apr 21, 2020 10:01 pm
The shape binder in my example references the original sketch. Not model edges or faces.
So why not use the sketches edges directly?
drmacro wrote:
Tue Apr 21, 2020 10:01 pm
what would prevent the use of another shape binder.
Why should it be prevented? You can use as many shapebinders to as many bodies, part models, draft elements, ... all under single body.
drmacro wrote:
Tue Apr 21, 2020 10:01 pm
if the shape binder stabilizes the model
It does not on its own.
drmacro
Posts: 2566
Joined: Sun Mar 02, 2014 4:35 pm

Re: Shape binder...modeling challenge

Postby drmacro » Sun Apr 26, 2020 6:36 pm

Just for completeness I figured I give the same model a try with only sketches, no shape binder or datums.

This model uses sketch edges from the initial sketch only and origin planes.
Attachments
Fig_8-57-2.FCStd
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Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."

My beginners, written treatise: Learning FreeCAD
freedman
Posts: 1786
Joined: Thu Mar 22, 2018 3:02 am
Location: Washington State, USA

Re: Shape binder...modeling challenge

Postby freedman » Wed Apr 29, 2020 9:13 pm

drmacro, In looking at your file it seems it was saved with Preferences-Sketcher-Visibility Automation "hide all objects that depend on the sketch" set to checked , is that true? I'm not exactly sure how this option is saved across platforms, when I open each of your sketches I don't see the model in the background.