FreeCAD add-on for a bare-bone assembly structure, using App::Link
An Assembly4 model is a standard FreeCAD App::Part object, and can be used with any FreeCAD tool handling App::Part objects. An Assembly4 Model can invariably be a stand-alone part, an assembly, a sub-assembly, and any combinations of these.
Any Assembly4 Model can contain (by App::Link) any other Assembly4 Model or any App::Part, but an App::Part cannot be used with Assembly4 to link by App::Link other App::Part objects. Parts and linked parts are placed to each-other by matching their Datum Coordinate Systems (PartDesign::CoordinateSystem, called here-after LCS for Local Coordinate System) using the built-in FreeCAD ExpressionEngine. No geometry is used to place and constrain parts relative to each other, thus avoiding a lot of the topological naming problems.
Important Note: Assembly 4 is not compatible with FreeCAD v0.18, needs :
- FreeCAD >=
v0.19.18353
Pre-built binaries on the v0.19 development branch can be found here
Assembly 4 is available through the FreeCAD Addon Manager (menu Tools > Addon Manager). It is called Assembly4 in the Addon Repository.
Note: Restarting FreeCAD is required after installing this Addon.
You can use the example assemblies to experiment with this workbench's features. Open one asm_something.fcstd file and try out the functions. There are ReadMe.txt files in each directory with some explanations. There are tutorials available to lear tu use Assembly4:
- a quick assembly from scratch
- a cinematic assembly in one file, using a master sketch
- a multy-layered assembly for advanced users
- a Lego assembly
- an architectural assembly
Assembly4 uses a very powerful feature of FreeCAD, the ExpressionEngine. Some FreeCAD object's parameters can be entered through mathematical formulae, that are evaluated by this ExpressionEngine. For Assembly4, it's the parameter Placement of the inserted App::Link object that is calculated, such that 2 LCS - one in the linked part and the one in the assembly - are superimposed.
You can find more informations in the detailed instructions.
An Assembly4 assembly is a FreeCAD App::Part container, and parts are inserted using App::Link links to App::Part objects in their original document, no shapes are copied, making assemblies very memory efficient. The original part's document can be in the same file as the assembly or in another file somewhere on disk.
Since assemblies are also App::Part objects, they themselves can be assembled in another assembly, allowing nested multy-layered assemblies.
To each part inserted into an assembly is associated constraint, which is an App::FeaturePython object in Assembly4, placed in the 'Constraints' group at the root of the assembly. This constraint object contains information about the placement of the linked object in the assembly.
At the time of this writing, there is only 1 type of constraint in Assembly4 : matching of LCS between 2 objects. It is foreseen in the future to extend the available types of constraints.
Each constraint contains an App::Placement property, called 'AttachmentOffset', which introduces an offset between the attachment LCS in the part and the target LCS in the assembly. This allows
It is also possible to insert a part into an assembly without any constraint and without using the ExpressionEngine. In this case the inserted part (its App::Link really) can be moved manually by the built-in FreeCAD dragger. Right-click on the link in the Model tree, and in the contextual menu choose Transform . It is also possible to manually edit the inserted link's Placement property.
This is then a raw interface between FreeCAD App::Part objects through the App::Link functionality.
-
2020.01.06 (version 0.7.7) :
Moved the turorials to the Resources directory
import libAsm4 as Asm4
Added a Help command (dummy placeholder)
Ported example2 to the latest Asm4 format -
2019.12.12 (version 0.7.6) :
Improved animation and datum import. -
2019.12.02 (version 0.7.5) :
Minor (but useful !) refinements for variables and animation. -
2019.11.24 (version 0.7.4) :
Added Animation command -
2019.11.19 (version 0.7.3) :
Added linkArray, a wrapper for Draft::LinkArray
Fixes for the Fasteners command -
2019.11.14 (version 0.7.2) :
Bug-fix for importDatum -
2019.11.11 (version 0.7.1) :
Bug-fix -
2019.11.05 (version 0.7.0) :
Support for screws & nuts from the Fasteners workbench
Added Variables to the Model
The model file format has changed, former assembly models can be opened but must be re-assembled. -
2019.10.11 (version 0.6.4) :
Improved assembly in single file
Various small fixes -
2019.10.11 (version 0.6.3) :
It is now possible to link parts from the same document as the assembly itself, allowing to make 1-file assemblies and still use all the other tools. -
2019.10.11 (version 0.6.2) :
Added page for Tutorial 1.
Fine-tuned some functions
Renamed icons in a consistent way -
2019.10.07 (version 0.6.1) :
Moved the code that was in Mod_Asm4 to the root, to be compatible with the FreeCAD AddonManager -
2019.10.05 (version 0.6) :
Ported to FreeCAD-v0.19-pre, with new syntax for the ExpressionEngine -
2019.07.23 (version 0.5.5) :
Fixed a bug in partLCSlist.findItems
New Datum Point in the Model -
2019.07.18 (version 0.5.4) :
A cosmetic update to fix a 25 year old Windows bug:
some UTF-8 characters in the comments were not accepted on some Windows 10 machines -
2019.06.15 (version 0.5.3) :
Now the LCS can be renamed, and they show up in the LCS list in the command placeLink as such.
It's only visual, the ExpressionEngine still uses the LCS.Name though -
2019.05.07 (version 0.5.2) :
added insertDatumCmd -
2019.03.18 (version 0.5.1) :
Part can now be linked without being placed: this is then a raw interface with App::Link
The instance can be moved manually with the 'Transform' dragger -
2019.03.12 (version 0.5) :
moved the actual code to Mod_Asm4 -
2019.03.11 (version 0.4.1) :
Added placement of Datum Point -
2019.03.09 (version 0.4) :
FreeCAD now imports as App
insert_Link launches place_Link -
2019.03.05 (version 0.3.1) :
added the RotX-Y-Z buttons -
2019.02.20 (version 0.3)
mostly working version -
2019.02.18 (version 0.1) :
initial release of Assembly 4 WB
Please offer feedback or connect with the developers in the dedicated FreeCAD forum thread.
This addon is hosted on a GitHub repository.
LGPLv2.1 (see LICENSE)