Important KiCad tip of the day:
Cut/Copy/Paste in KiCad is not thoroughly and consistently implemented in KiCad. If you want to pull a section of a PCB from one design into another, you can’t do the obvious and simply cut and paste. Instead, you have to open PCBNew in standalone mode, i.e. start PCBNew.exe instead of Kicad.exe. When you do this, KiCad exposes a menu item called “Append Board…” You use File->Open to open the base design the normal way, and then click File->Append Board… and select the board you want to copy from.
After hitting OK, you’ll find the entire board you want something from is now attached to your mouse pointer. You move somewhere that doesn’t overlap with your main design, click to stick it down, and then cut and paste whatever bits you want and discard the rest. At this point you’ll save your modified file and be all happy, right?
Nope. KiCad gets a bit overly ambitious here. When you import using “Append Board…”, KiCad also imports all the board settings from that board and overwrites the ones in the design you want to update and keep. What’s the significance here? Well, if you defined any custom net classes in the keeper board and they’re not present in the board you’re importing from, all you’ll have left are the ones in the import board. Same goes for any parameters such as min via diameter, min drill, min track, etc.
It can be quite a shock to import a bit of a PCB, save your file, run DRC, and suddenly find the design that passed 100% before the import now has 50 DRC errors. Ask me how I know…
If you’re smart and make versions of your design in separate folders as you progress, then the cure is simple. You just open File->Board Setup, hit the “Import Settings…” button in the bottom left, select the previous version of the design (which presumably has the same settings as the latest version that just got borked), and hit OK. All the settings will be updated and you’re back where you were.
On the other hand, if you’re the type who only has one version and keep constantly updating it so it’s always the latest, well… you’re screwed. But now you have the impetus to learn good work habits.
Is copying and pasting between PCBs a common thing? Nope, but there are times you need it. At least now you now the side effects of using “Append Board…” and won’t be surprised.