Intro

If you design PCB most likely you also maintain components library (symbols and footprints). In any modern ECAD (Altium Designer, KiCad, Allegro...) 3D model of the components if important part of the PCB project design, because it's give a chance to make correct placement by using exact virtual copy of real components.

How to make it using MCAD FreeCAD?

Most of MCAD (Mechanical CADs) have the function of doing projection of 3D model to 2D drawing. You can use open software FreeCAD for creation 2D (.dxf) drawings from 3D (.step) models and just follow next steps 🙂

Open 3D file (.step if preferable)

File -> Open (Ctrl + O)

Select Draft Workbench

Choose view from Bottom

Set BOTTOM view (press it on Cube) or press 5 on keyboard:

Highlight 3D Model

Choose model in the Tree view, it should glow green.

Make 2D Projection

Press Modification -> Shape 2D view

See Projection

Now you can see new Shape2DView in the Tree view (this is projection drawing):

Save Drawing

Highlight created draft object (green) and press File -> Export (Ctrl + E), type any  file name and choose Autodesk AXF 2D (.dxf) format:

Check 2D Drawing

After export (saving) you can open and check file in any viewer software (e.g. CAD Assistant):

Altium Import

So, let's see how to use created 2D projection with real example of 8191 metal terminal:

I already have this component's footprint in the library:

Press Import -> AutoCAD:

Choose projection file. It's important to choose scale mm and locate AutoCad (0,0) to the actual footprint center:

As you can see it's definitely something slightly wrong with the pads locations or 3D model (after comparison with the datasheet downloaded 3D model turned out to be a little wrong and needs correction).

(*0.01mm -> 0.1mm increased for better viewing)

More Examples

Conclusions

🟢 This small improvement can reduce possible errors in pad sizes and shapes

🟢 Precise outline make possible super precise placement.

🟠 Most of downloaded 3D models of the components have incorrect origin location, so it's required to correct it to the actual center using any MCAD, so you don't need to make rotation of offset in the ECAD.