When you have to reduce the size of your PC board

Sorry if this is the wrong category, I didn’t find one for PCBNew…
I’ve had to reduce the physical size of a previously made PC board.
I did so by chopping off the top inch or so of the board.
I realize the origin of everything is the upper left, so I used the menu icons
for “Set the origins of the grid” and “Place Aux origins” at the new upper left
of the new layout, but I still have one line showing in Edge Cuts layer
that I can’t delete which must still be pointing to the “real” origin.
Do I have to somehow select Everything and move it to the old origin
or is there a way to do this otherwise?
Pic attached.

I changed the category to Layout for you.

You can select the line by pressing the mouse button on the right side of the line, then drag the mouse cursor to the left of the line and release the button.
When the line is selected, it’s highlighted, and a white square appears on each end, and then you can drag the end point with the square to your new location.

Dragging from right to left selects everything in and everything crossing the box boundaries.
Dragging from left to right only selects objects that are completely in the box.

You can add to a previous selection by holding the [Shift] key all the time.

For modifying Edge.Cuts, I usually set the grid to a coarse value, such as 1mm. This makes it easier to match the endpoints of lines on Edge.Cuts and to draw horizontal and vertical lines.

Another way to select a line from Edge.Cuts easily is to zoom in until it is 20 or so pixels wide, and then click on it.

I place Aux origins in some distance from the lower left PCB corner (to have whole PCB up and right of that origin). That way I have all coordinates in gerbers positive (y in gerbers increases normally and not how it is in PcbNew).

Out of curiosity, why “in some distance”, why not exactly on lower left corner?
Also, what is the difference between the Aux origin and the actual origin?
Thanks for your help!

Coordinate system, grid and origins in Pcbnew (especially version 5.99)

There is no requirement that an Edge Cut or any other feature must start, end, or pass through the page, grid, or aux origins. You can place any feature anywhere you want.

(Not quite true, as the maximum distance from the page origin is 2^31 nanometers. Still, 2.147 meters is pretty much “anywhere” on a PCB).

There are 2 reasons, none of them seriously important.

  1. I came to KiCad from Protel 3 (a program from 1997). There I have only positive X (to right) and positive Y (up), and can’t go to negative coordinates. As some elements (like connectors) sometimes have their parts being out of PCB we used to set bottom left PCB corner at 100/100 mils (if something is more out of PCB then bigger distance from origin). Thanks to that we got everything at the pictures we output as documentation. Also it can happen that after placing element its reference or value can be placed out of PCB (I don’t know the rule - they are really placed randomly near element). If I have PCB corner at 0,0 I will be not able to get it with mouse as I can’t move mouse to negative coordinates.
    Gerbers of each PCB I send to my brother to verify by second eyes pair. When I send him first time KiCad gerbers he was very surprised why I have moved PCB to negative Y coordinates.
    So I place Aux origin to have everything ‘as usual’.
  2. The Aux origin mark disturbs view of PCB so I prefer to have it out of it.

The actual origin is (in 5.1.9) unmovable. In KiCad I work around the actual origin (I modified the frame to be only small cross at 0,0). I frequently have PCBs with some kind of symmetry. That helps me to place for example holes by writing their coordinates without need to calculate offset. If I have the case picture (for example DIN-rail cases) with dimensions organised around axes of symmetry then I place my PCB to have 0,0 at the same point as axes crosses and I get the same coordinate system as in mechanic drawing. I have never used any mechanic CAD program to test if everything fits. Once (in such DIN-rail case) I used two PLCC LEDs and long vertical optical fiber standing on them then I specified the holes in case at the same positions as my LEDs at PCB. I think that if I had to calculate such things the chance of mistake would be bigger. All my LED (also THT) footprints have their origin at LED center and not at pad 1 center.
In Protel I used the same strategy, but using tools accessible there (you can move origin when you wont and then all coordinates are read/write regard these new position).

Piotr likes to use the (hardcoded) origin (0,0) as an important location in his designs, but this necessitates removal (modification) of the page layout.

I have recently decided to use (127, 127) as an “important” location for the PCB. It can either be a corner of the PCB itself, or pin 1 of a dominating THT connector. The reason for this location is that it fits both on a metric and on an imp. grid without adjustments of offsets for the grid. This way it’s easy to put THT connectors on a 0.1" grid (for breadboard and matrix board compatibility) and use metric measurements for PCB outline and mounting hole locations.

In the end it all does not matter much, and mostly boils down to personal preferences.

1 Like

This topic was automatically closed 90 days after the last reply. New replies are no longer allowed.