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Cutting PCBs

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About the Mill

The CNC machine at the space was entirely sourced from member’s donations.


Motherly Housekeeping or ‘CNC Mantras’

  • You can’t buy new eyes:


If the spindle is spinning you MUST be wearing safety glasses.

  • The computer can speed up the cutting but it can’t replace broken bits:


If uncertain about plunge/travel speeds then be conservative, you can always crank up the speed in Mach3/EMC while cutting is in progress.

  • Cut the air first, it’s quick and free:


When using the mill the first few times it’s worthwhile doing a test cut first in the air above the actual workpiece. If you have made scaling, origin, speed, orientation, etc errors then they are easier to spot and correct before you ruin the machine/material/bit.



Hints and Tips

The most current tips to get your PCB cutting working well is in 'CNC Tips and Tricks'. The material below here may no longer be needed.


Making PCBs

This assume you’ve followed the steps in 'designing PCBs' and created the gcode files for your boards.

Tools used:


  • Cutting the tracks of the circuit. V-cutter

  • A Drill bit is used for the through-hole parts

  • A Router bit is used for cutting the board free when finished.  


Operating the controls on the mill

  • The red ‘drive’ switch controls whether the stepper motors are powered
  • The spindle is controlled by a separate power supply above. Turn on the power via the rocker switch and press the black button to increase the speed. The red button stops the spindle. Most tools cut well at 75% speed (3 button presses).
  • Please note that the emergency stop is not reliable (software interface). To shut down the mill in a hurry use the ‘stop’ button in Mach3
  • When finished, turn off all the equipment


Using Mach3 with Premade G-code

  • Open ‘Mach3’ mill from the desktop
  • Power on the mill
  • Check that Mach3 is ready to run (i.e. the ‘reset’ light isn’t flashing). If not, clear the problem and click ‘reset’ to continue
  • Use ‘FileOpen’ and select the g-code you want
  • Clamp your material securely on the bed
  • Zero your X & Y axes over where you want the origin to be. (Look at the display carefully to ensure the origin is where you expect it in the code. Top and bottom layers of circuit boards are located differently)
  • Change to the tool you need using the two flat spanners near the mill
  • Zero your z-axisfor the new tool (instructions below)
  • Make sure the spindle is moved back up in the air and free to turn after zeroing
  • Start the spindle
  • Click ‘Cycle-Start’ in Mach3 and it will start milling

Note: PCB-gcode does not currently support setting mill feed speed manually. Before running the ‘mill’ file you should change the ‘Feed Rate Override’ down to 50% or below to ensure it cuts at a safe speed.

How to Zero the Z-axis

It’s very important to zero the z-axis for each new tool you put in the machine.
Differences as small as 0.1mm can be the difference between a working and a failed board. Do this step carefully.

  1. Put Mach3 in a slow jog mode of 20% or below. (Press ‘tab’ to show the control pendant on screen, and use the +/- buttons to set the speed.)
  2. Position the tool tip above a nice flat piece of the board using the arrow keys and  use the PgUp/PgDn keys to lower the tool tip to near the surface.
  3. Use a thin piece of paper (e.g. a4 office paper) between the tool tip and the board. Use a series of taps on the PgDnkey and make small movements downwards until the paper is just no longer free to move.
  4. Click the ‘Zero Z’ button on Mach3 to save this position as the correct Z-level
  5. Raise the head up again before turning on the spindle.


Making other things with the mill

So the mill is capable of doing much more than just PCBs. There’s a large work envelope, and you can do any combination of drilling, milling or routing

Inkscape is a good program to draw up DXFs for export to cambam, if you’re wanting 2D designs.


Sources for Tools & Equipment


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