KicadStepUp Workbench

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Introduction

KicadStepUp Workbench is aimed at helping both KiCad and FreeCAD users in collaborating with electrical (ECAD) and mechanical (MCAD) design.

Background

KiCad (website) is an Open Source Electronics Design Automation Suite. It allows the user to design an electronic schematic diagram and then a single or multilayer printed circuit board (PCB) using an extensive library of parts. The great thing is that using FreeCAD with the KicadStepUp Workbench is the official KiCad way to create 3D parts for electronic components for KiCad. The libraries are hosted here, so everyone can create and check in parts.

KiCad's GUI philosophy is a bit different compared to FreeCAD, especially when it comes down to creating elements and moving them around. However, since KiCad has been used in production for years, there is excellent documentation, e.g., a very good "Getting Started" document. Additionally, each tool has its own manual.

If one does not know KiCad yet, it's recommended to complete a stand-alone PCB according to the Getting Started Guide to understand the concepts involved. Although some topics like adding new schematics and footprints to a local library seem to be of little interest for the beginner, in practice they are often encountered quickly after starting a serious project.

For all these KiCad concepts one can find a feature of some sort in the KicadStepUp workbench. So knowing those makes it a lot easier to understand how to use this workbench.

Features

In progress

Load KiCad board and parts in FreeCAD and export it to STEP (or IGES) for a full ECAD MCAD collaboration
Load KiCad footprint in FreeCAD to easy and precisely align the mechanical model to KiCad footprint
Convert the STEP 3D model of parts, board, enclosure to VRML with Materials properties for the best use in KiCad
Check interference and collisions for enclosure and footprint design
Design a new PCB edge with the Sketcher Workbench of FreeCAD and PUSH it to an existing KiCad PCB board
PULL a PCB edge from a KiCad PCB board, edit it in the Sketcher Workbench of FreeCAD and PUSH it back to KiCad
Design a new footprint in FreeCAD to get the power of Sketch in footprints
Generate Blender compatible VRML files

Installation

KicadStepUp is part of the external workbenches, and can be automatically installed using the Addon manager which is included with FreeCAD 0.17 and up, under the Tools → AddOn manager menu.

Usage

In progress

General Approach

The basic idea of KicadStepUp is to synchronize data between the two applications. For home use you might have FreeCAD and KiCad running at the same time. Professional users can work on the same files (e.g. on a central server) and have specialists on mechanical CAD (MCAD) working in FreeCAD and electronics experts on electrical CAD (ECAD).

KicadStepUp will convert standard FreeCAD files to KiCad files and vice versa. That way each application can work with its native data files. Projects can be used without the other application or KicadStepUp installed. That is also the reason that no plugin on the KiCad side is required.

It's important to note that the differences between the two programs impose some difficulties for a full data exchange.
One example is that the Sketcher used in KiCad to define the board outline is very limited compared to the Sketcher Workbench of FreeCAD. So in order to synchronize back and forth, the sketch content cannot be more complex than the KiCad Sketcher can handle. From a FreeCAD point of view, that means you may want to avoid using some of the FreeCAD sketch features. KicadStepUp offers workarounds that might be more difficult to understand if you do not have this background.

Basic Workflow

A collaboration can be started with a new or an existing project. We consider here a new project to keep things simple:

Create a new KiCad Project anywhere you like. Lets name it "KsuTest"
Open the PCB Editor and create on the layer "Edit.Cuts" a closed outline. Shape does not matter, we will overwrite it anyway.
Create a new FreeCAD file for the PCB, the name does not matter. *
Create a sketch with an outline of the desired PCB. Lets name it "pcb design" (but could be any other name) and put at least one circle into it for a hole.
you may use any FreeCAD features to include holes, cutouts, and outer shape to other components you might have. We assume here you would use Sketcher features as Dimensioning, Constraints and Work geometry in your sketch.

If you are using PartDesign Workbench for creating the sketch there is no need to create a PartDesign body, since we are not going to pad this sketch.
Switch to the KicadStepUp Workbech
Select the "pcb design" sketch
Select the Toolbar button "Push Sketch to PCB Edge" or the menu ksu PushPull/ksu Push Sketch to PCB
- first a dialog will open with defaults "Edge.Cuts" for layer and "0.16" for line width. Keep those defaults.
- next a file dialog will open. Click to your KiCad "KsuTest" project, where you should see a file "KsuTest.kucad_pcb". That is the PCB file with the temporary outline we created before. Select it and confirm to replace the old file.
  Now a dialog should say "new Edge pushed to kicad board!"
  if you forgot the 2nd step, the push operation might fail as a pcb file must exist and it must not be empty.
Close and re-open the PCB Editor in KiCad. **
The shape from the FreeCAD sketch should appear.
Go over the circle with the mouse and press m on the keyboard to move the circle. Click to place it in another position. Press the "Save" toolbar button on the top left.
Switch to FreeCAD and select in the KicadStepUp Workbech the tool button "Pull Sketch from PCB" or the menu ksu PushPull/ksu Pull Sketch from PCB
- first dialog with default layer "Edge.Cuts" and three choices will open. Select choice "replace PCB and Sketch in current document" ***
- next a file dialog should show again the file "KsuTest.kucad_pcb". Select it and press Open
  You should see your PCB as a 3D model. Note that the hole has moved compared to your "pcb design" sketch.
  
  In the tree appears a new structure with a yellow Part Container with the KiCad Filename and within another Part Container with "Board_Geoms_e63b" (the part with the number probably different). In the second container there are the following three files. Do not change any names in that structure, because KicadStepUp uses them to find the parts to update.
  
  Do not forget to save your file

Local_CS_e63b      the PCB origin.
                     same as the origin in "pcb design" sketch
Pcb_e63b           3D object with the PCB.
                      Don't edit, it will be overwritten by KicadStepUp
PCB_Sketch_e63b    sketch with all parts of "pcb design" sketch that KiCad recognized.
                      all others were deleted. Also note that if you change this sketch
                      and recalculate, the 3D object will not change.

Try to make another PushPull round trip: adjust your "pcb design" sketch to the changes from KiCad, add some other change and start again. Do that a few times to appreciate how quickly and naturally this procedure becomes in a very short time.

Now you can use the new 3D PCB file to align 3D components as connectors, buttons, switches, fasteners, etc., or add it to your assembly if you have a larger project.

This only shows the very basic way KicadStepUp works. You are still missing a lot at this point, e.g., footprints and 3D parts, but from here it's a lot easier to start exploring KicadStepUp on your own. Use the documentation PDF file in the menu ksu Tools/Demo

Notes:

As long as the name of the created structure (and its parts) is unchanged, any workflow interactions will just update the structure. If you change any names, a new structure will be created each time.
It is not required to have KiCad running to update KiCad project files. Actually, KiCad does not even have to be installed on the PC.
The standard approach is to use the same sketch on both sides, KiCad and Freecad. Any changes will be synchronized to the other application. This is the most natural and clean way to work with KicadStepUp .
However, this causes a problem if you want to use any of the following features in your sketch to define your PCB shape: dimensions, geometry constraints, construction geometry (blue lines), or external linked geometry. There is no clean way to do this, because KiCad does not know any of those features. That means that on the round trip between the applications, any of those features will be deleted. There is no real solution for that problem, just a selection of one of several workarounds. So if you want to use any of those features, that means you must define the PCB shape in FreeCAD only and sync in one direction toward KiCad. Any outline changes done in KiCad need to be added manually on the FreeCAD side. This might make sense, e.g. if future changes from the mechanical side are much more likely than from the electrical side. There several ways to do it:
- Put the design sketch inside the KicadStepUp structure, and select "replace PCB and keep Sketch in curr. doc" every time you import back from Kicad.
- Keep the design sketch outside the KicadStepUp structure. Ignore the sketch imported from KiCad.

The second choice has the advantage that changes in KiCad can be traced to the original sketch, and the FreeCAD sketch is protected against an accidentally wrong import choice. The described workflow uses this approach to make sure the issue is well understood. From there it's easy to switch to modifying the KicadStepUp supplied sketch with none of the more advanced FreeCAD features.

To use KicadStepUp with a FreeCAD assembly (> V0.19) you could add a new file for the PCB. After the workflow above has been run once add the 3D object for the PCB to your assembly like any other mechanical part. Make sure you save the file when it was updated by KicadStepUp (Important: KicadStepUp writes to FreeCAD memory, not to FreeCAD files).

Please see the KicadStepUp Cheat Sheet for the other features.

References

Author: Github: @easyw | FreeCAD Forums: kicad StepUp: ECAD MCAD bidirectional collaboration
Source code on GitHub: https://github.com/easyw/kicadStepUpMod

Side Note about External workbenches

FreeCAD workbenches are easy to program in Python, there are therefore many people developing additional workbenches outside of the FreeCAD main developers.

The external workbenches page has some information and tutorials on some of them, and the FreeCAD Addons project aims at gathering them and making them easily installable from within FreeCAD.

New workbenches are in development, stay tuned!