Summary of the process to make a pcb with a CNC 3018 (grbl) from the scratch
- Eagle phase – Preparing Gerber & Excellon files to flatcam for PCB milling
- Schematic Design
- Board design
- Export Gerber Files & Excellon files
- Build the tool path gcode files with flatcam
- CNC 3018 job preparation
- Put the V30º bit tip 0.2 on the spindle
- Place the board to mill in the CNC
- Put the alligator tools on place for z probing
- Load the gcode for milling tracks
- Set home and z probe
- Do the heightmap of the board
- Send the gcode to the CNC
- Put the drill bit on the spindle
- Load the gcode for drilling holes
Hardware
- CNC 3018
- Mill bits
- Drill bits
Software
- Eagle
- Flatcam
- Candle
Mill bits
What bits we shall use to mill a PCB?
- 30 to 60 degrees V bits with 0.1 or 0.2 tips
- PCB with 35µm copper layers and on those I am using 22k RPM, 30 degree V-bit with 0.2mm tip
RPMs and feeds: depending on the machine and spindle.
ex: 8000 rpm, 150mm/min
1) *Most important improvement* – modify (or replace) your controller so that it can accept an electronic Z-probe input, and get some software that can do mesh levelling. Clean the board first then use an aligator clip on one edge of the board and another on the milling bit. I then probe across the project cutting area using a 10mm grid or thereabouts.
2) *Second most important improvement* – hold the board in deliberate curve and clamp the edges well. I 3D printed a wasteboard for mine to suit 10cm x 7cm boards, and it has a 1mm difference between the centre and the two long edges. I then have two hold-down clamps that run the entire length of the long edges. This takes out some unknown warp in the board and makes it *much* stiffer against the cutting tip. The mesh levelling will happily take care of the curve.
Other tips in no particular order:
3) If you’re using FR4, you’ll need good dust extraction, the fibreglass dust is harmful. I’ve found the safer FR1 / FR2 on ebay and aliexpress plenty of times.
4) 30 degree carbide v-bits are fine for the traces. I think I’ve got mine set up for 0.2 to 0.25mm depth, but you’ll need a stiff & accruate board for it to work (see #4 and #5). Not all the bits are as sharp as each other, in a pack of 10 I usually have to discard a couple that just seem to make poor cuts or have trouble starting.
5) I think I’m using a 0.8 or 1.0mm endmill for cutting the boards free, usually about 0.4 to 0.5mm per pass. For the through-holes I use 0.8mm drill bit, it’s a good balance for most parts and occasionally I have to enlarge them by hand to 1mm for for bigger components.
6) Within reason, no issue making traces wider. On your board above you’ve got massive amounts of space, they could be 2mm wide without issue. I’m typically doing 1mm for signals and 2.5mm for power unless I need to route something tight.
7) The gap between traces can be fairly small, typically mine is only the cutter width so maybe 0.3mm. Just cleanup the surface with a brass wire brush or kitchen scourer to knock off any dags that might bridge it.
I use something like these for my traces, cant remember if I bought 0.2mm or 0.1mm though. Pretty sure it was 0.2mm.
https://www.ebay.com.au/itm/5pc-3-1…de-Engraving-Bit-CNC-Router-Tool/163670025361
A set of twist drills for holes ranging 0.3 to 1.2mm, but really I just use the 0.8mm:
https://www.ebay.com.au/itm/0-1-3-0…Steel-Carbide-Set-Rotary-Milling/312808774833
And then a stack of 1mm endmills for curtting out the board:
https://www.ebay.com.au/itm/10pcs-1…-Drill-Bit-Milling-Cutter-Set-AU/174003266531
Last edited: May 27, 2020
May 27, 2020#5