https://github.com/gbroques/freecad-dynamic-linked-object

Example of using a dynamic linked object in an assembly.
https://github.com/gbroques/freecad-dynamic-linked-object

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Example of using a dynamic linked object in an assembly.

• Host: GitHub
• URL: https://github.com/gbroques/freecad-dynamic-linked-object
• Owner: gbroques
• Created: 2021-04-01T01:40:31.000Z (almost 4 years ago)
• Default Branch: master
• Last Pushed: 2022-11-05T22:05:46.000Z (over 2 years ago)
• Last Synced: 2024-11-13T03:15:03.510Z (3 months ago)
• Topics: assembly, freecad, link
• Homepage:
• Size: 343 KB
• Stars: 0
• Watchers: 3
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# FreeCAD Example: Dynamic Linked Object

Link (internally `App::Link`) is an important new feature introduced in FreeCAD 0.19 assemblies.

This repository aims to layout one pattern for complex assemblies involving *dynamic linked objects* which aims to reduce duplication of assembly related logic such as orientation, positioning, or number of instances.

## Example

To illustrate the dynamic linked object concept, consider a table with four legs.

Each leg has two different variants:

* Round

* and Square

The variants can be controlled by a parameter in a spreadsheet.

For our table model, we'll create **five** separate documents:

1. `TableTop.FCStd` - containing the top of the table.

2. `RoundTableLeg.FCStd` - containing a ''round'' table leg.

3. `SquareTableLeg.FCStd` - containing a ''square'' table leg.

4. `Table.FCStd` - containing the assembly of the table top and legs.

5. `Spreadsheet.FCStd` - containing a spreadsheet to drive the model.

Our simple table model will define the following parameters in `Spreadsheet.FCStd`:

1. `TableTopSize` - Dimension of the **square** table top.

2. `TableTopThickness` - Thickness of the table top.

3. `TableLegSize` - Size of each table leg. For Square leg, this is the dimension. For Round leg, this is the diameter.

4. `TableLegHeight` - Height of each table leg.

5. `TableLegVariant` - Controls the style of table leg. Possible values include "`Square`" and "`Round`".

`Table.FCStd` is where the dynamic linked object concept is illustrated.

The goal is to *not* duplicate the following assembly logic for each table leg variant:

* Each table leg must appear **four** times underneath each corner of the table top.

How this is accomplished:

* The `TableTop` and one of the TableLeg objects (Round or Square) are linked into the `Table` document.

* The TableLeg link is renamed to `TableLeg` and the "Linked Object" property is changed to the following conditional expression:

  * `<>#Spreadsheet.TableLegVariant == <> ? <>#<>._self : <>#<>._self`

* Each table leg must appear **four** times underneath each corner of the table top so an [orthogonal array](https://wiki.freecadweb.org/Draft_OrthoArray) is created using the parametric `TableLeg` link as a base object.

![Dynamic Table Leg](dynamic-table-leg.gif)

## See Also

https://wiki.freecadweb.org/Dynamic_linked_object