I'm not an expert on it, but sometime ago I did a double side PCB, and to save the good reference in both sides I did the next:
- I put 4 vias with a unused diameter ( 3 mm. in my case), in a symmetrical position, in this way:
------------
- O........O -
- ............ -
- ............ -
- ............ -
- ............ -
- ............ -
- O........O -
------------
- I fixes the PCB on a wood base, and mill the upper side and drill all the vias.
- Then, I put 4 calibrated rods on each 3mm. drills, and fix the bottom side with this reference. The position was OK, and I can't remember the accuracy, but it looked perfect.
NOTEs: If you left the rods while milling, take care the tool don't touch them.
Be sure about the symmetry you need in the bottom side G-Code.
I expect it helps you. |