Overview

PCB milling is an alternative to etching for those who have a home CNC machine and dont like using chemicals.

It is the milling process used for removing areas of copper from a sheet of printed circuit board (PCB) material to recreate the pads, signal traces and structures according to patterns from a Gerber layout export.

Very cheap home CNCs (like CNC 3018PRO etc) are pretty much capable of doing CNC milling.

PCB Milling process

My approach to PCB milling that I use for CANSim making:

  • I use custom-made GRBL-based CNC

  • For milling I use 60 deg, 0.2mm tip V-carve. It makes wide cuts, but works for my tasks. For finer cuts, consider 30 deg V-carve. https://hobbycnc.com/tool-width-calculator/ can be used to calculate cut width.

  • To drill holes I use “milldrill” process with 0.7mm corn mill, to avoid any tool switches for drilles. It doesn’t make sense to make holes less than 0.7mm anyway for manual soldering

  • PCB is cut with the same 0.7mm corn mill.

Process is:

  • prepare Gerber Export (I use EasyEDA, but every sofware capable of exporing gerber files will do)

  • run pcb2gcode (https://github.com/pcb2gcode/pcb2gcode) with the following millproject file (create “out” directory before!):

      output-dir=./out

  # source files (replace with you naming!)
  back=Gerber_BottomLayer.GBL
  outline=Gerber_BoardOutlineLayer.GKO
  drill=drill_merged.drl

  # common settings
  path-finding-limit=4
  backtrack=10

  # common machine specific settings
  nog81=true
  nog64=true
  nom6=true
  metric=true
  metricoutput=true
  zero-start=true
  zsafe=3mm
  zchange=50mm

  # milling (60 deg, 0.2mm tip V-carve)
  # https://hobbycnc.com/tool-width-calculator/
  zwork=-0.1mm
  mill-feed=180mm/min
  mill-vertfeed=100mm/min
  mill-speed=12000rpm
  mill-diameters=0.31547mm
  isolation-width=0.5mm

  # drilling (milldrilling) (0.7mm corn mill)
  min-milldrill-hole-diameter=0 
  milldrill-diameter=0.7mm
  zmilldrill=-1.7mm
  zdrill=-1.7mm
  drill-feed=80mm/min
  drill-speed=12000rpm

  # cutting (0.7mm corn mill)
  cutter-diameter=0.7mm
  zcut=-1.7mm
  cut-infeed=0.6mm # 3 passes
  cut-feed=120mm/min
  cut-speed=12000rpm

  • run resulting back.ngc, milldrill.ngc, and outline.ngc on your CNC.

  • solder and have fun!

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