Assembly3 workbench is yet another attempt to bring assembly capability to FreeCAD. There is the original unfinished Assembly workbench in FreeCAD source tree, and Assembly2, which is an inspiration of this workbench, and with some code borrowed as well. The emphasis of Assembly3 is on full support of nested and multi-document assemblies.

You can find more details at Assembly3 wiki.

Update: I have added a donation button. Feel free to show your support, and thanks in advance!

Although Assembly3 workbench is written in Python, it depends on a few external python extensions. In addition, it relies on quite a few FreeCAD core changes to work properly. At the moment of this writing, these changes have not been merged into upstream yet, and only exists as a forked branch. To save you all the trouble of building FreeCAD yourself, I release Assembly3 along with the pre-build FreeCAD for all three major platforms. If you want to build everything yourself, please check out the build instruction here.

The design of Assembly3 (and the fork of FreeCAD) partially follows the unfinished FreeCAD Assembly project plan, in particularly, the section Infrastructure and Object model. You can find more details at here.

Before starting to use the Assembly3 workbench, it is necessary for the user to be familiar with a few new concepts introduced by the forked FreeCAD.

You can find instructions on common operations along with some tutorials at here.

This section is for those who have used Assembly2 before. Here is a brief list of comparison between Assembly2 to Assembly3.

• Assembly2 supports only one assembly per document, so the document can be considered as the assembly container.

  Assembly3 has dedicated container for assembly and supports multiple nested assemblies per document.

• Assembly2 has dedicated object for imported child feature. The child feature's geometry is imported as a compound, and can be updated by user in case of external modification of the geometry model.

  Assembly3 has no special object for imported feature, although the feature may be added through a link under some circumstances. Simply drag and drop feature into an Assembly container, even if the feature is in another document. Any modification of the feature is instantaneously visible to its parent assembly. The FreeCAD core provides various commands to help navigating among nested assemblies and the linked child features, import the external feature into the same document of the assembly, and export the child feature into external document.

• In Assembly2, the imported child feature acts as a container to group related constraints. There is no visualization of the geometry element in the constraint.

  The Assembly3 constraints are grouped under the parent assembly, each constraint acts as a container of its referring geometry ElementLink, with enhanced visualization support. Simply right click the ElementLink and choose Link actions -> Select final linked object to jump to the actual geometry model object owning the geometry element.

• Assembly2 has a dedicate task panel for degree of freedom animation.

  Assembly3 is currently lacking of similar functionality. However, it does allow you to interactively drag any part of the assembly under constraint in real time.