Launch your milling control software and start a new session. For this guide I'm using the Otherplan app to control my Othermill machine.
To accommodate our double-sided copper clad board, specify the material as Double-Sided FR-1. Doing so should give you the following dimensions:
- X: 127mm
- Y: 101.6mm
- Z: 1.64mm
Set the material's origin to X:0, Y:0, Z:0.
Note that I'll be milling a single pin for this guide, but you likely want to add more to make use of the entire copper board.
Import the vector file you created and set the following variables for it:
- Invert within cutout
- Engraving depth: 0.5mm
- 1/32" flat end mill bit
The "invert within cutout" setting (found in Otherplan's "Advanced" settings) will make the milling software use the empty/transparent areas for engraving, and the filled/black areas as copper to be left untouched.
Using an engraving depth of 0.5mm will make it easier to keep paint within the engraved and away from the raised copper.
I've found that 1/32" is the smallest size bit which holds up well to repeated use. Smaller bits tend to break too often, and larger bits don't allow for enough detail on pins.
You can mill your design using multiple sized bits for increased efficiency and speed or use a single small bit for simplicity. Depending on your machine's accuracy, using a single bit can produce cleaner results but takes considerably longer than a multi-bit approach.
Use strips of double-sided tape to secure the copper board to your mill's bed. Be sure the the board is mounted squarely with the left and front edges of the bed.
Connect power and USB to your milling machine and begin the milling process from the software UI.
Once the mill is complete, use a vacuum to remove excess dust and peel the board from the bed with a flat scraper or putty knife.
Peel off your finished piece and remove any remaining tape from the back. Inspect the piece for stray copper burrs and remove them with tweezers or a blade.