I need to place very small .089" holes (for 2-56 screws) in very precise locations so that the finished PCB will mount to another structure. I was hoping to just import a .dxf file with those holes (no pads, just holes) that would subsequently generate output to a drill file.
My ultimate goal is to CNC mill my own PCB after running the Gerbers and Drill files through something like pcb2gcode or similar software. My smallest bit size is .09375 (3/32") so I can’t just add the holes to Edge-Cuts and CNC the holes. I wanted to have a separate CNC gcode file to use with my #43 .089" CNC drill bit.
If I had to place mounting holes as precisely as you imply, I would start in the native program (Autocad, Solid Works, etc) that defines the mechanical structure. I’d use that to carefully pick off and record the positions of the mounting holes.
Then I’d go to KiCAD and define the mounting holes and all their details as pads or footprints - plate through/NPTH, solder mask, surrounding keep-out zones (don’t forget to allow for the washer under the mounting screw, if used!) or grounding pads, silkscreen outlines, etc. Finally, I’d place those mounting holes in the EXACT locations (out to about 40 decimal places, if that turns you on) I got from the mechanical design. (You do this with the “Edit” or “Properties” menu for each of the holes.) It’s more work than just plunking a .dxf file into PCBNew, but it gives you explicit control over ALL of the details.
I appreciate the suggestion but that’s more work than I want to do. Here’s what I did:
I created a .dxf file with the holes and imported it into the “Dwgs.User” layer. I also created a 2-56 mounting hole footprint. Then I just zoomed in real close to to each of the holes shown in the “Dwgs.User” layer and inserted the 2-56 mounting hole in the center. That should give me more than enough accuracy without having to enter the coordinates of every mounting hole (there are about 14) in the PCB.
I’ll be interested to see if anyone else has any other suggestion for doing this.
The dxf import has got very tiny marker holes in it (0.4mm) and the footprint for the NPTHs has got a cross hair. The hole from the dxf file that’s on the edge.cuts layer will ‘vanish’ in the drill hole definition that way, but I can leave it there for reference (surely could go for 0.1mm or less even).
Considering the tolerances of the fab house for drilling the placement at 0.01mm grid is better by a factor of 10 or more.
I have a somewhat similar problem, although not with holes. I have two mating boards. The female connector of the first board basically defines the position of the mating male connector on the other board (pentagonal shape). Now, the pentagonal board needs to be centered along the blue axis in order to satisfy tight space constraints… I am not sure what the best way to proceed would be. I have been using FreeCAD and StepUp, but I think this is pushing the limits of KiCAD… Maybe this is a good reason to switch to v5? I still need the stability, though…matingpic.pdf (82.1 KB)
So what is the actual problem there?
I don’t use FreeCAD (yet), so can’t help you with it in particular… but I could get you dxf files for importing into KiCAD if I knew the dimensions of the boards and the distances of the connectors to the centers?
