readme.md
Workflow


  
Note: For all operations, keep grbl software running and maintain XY home position.
  
  
Note: CADLAB.io view of github repo.  Login with google account.


PCB Prep


Clean the PCB with metal polisher to remove oxidation.  I use <![CDATA[]]>Brasso<![CDATA[]]>.  PCB should be shiny and clean.
Spray paint the PCB.  Ideally would use solder mask, but the epoxy material is hard to fully ablate.  Paint ablates nicely, though it is prone to scratching.


Design Prep


Panelize PCB using KiKit.  Use to provide frame and tabs with mousebites.  The kikit.sh script performs the process.
Load the panelized PCB into KiCAD.
Export a PCB image for laser ablation of the paint to expose the trace isolation areas.  Use the KiCAD "plot" function.  The image below shows the settings, assuming we're exposing the back side copper. 


PCB Fabrication


Tape down PCB on mill.  Rough cut the PCB to size if that makes sense.
Expect to route/drill through the PCB into the supporting material, so use a sacrificial material.
Drill all holes, including tooling holes.


It is recommended

Route out panel from larger PCB.  Limit size of PCB we're working with to maintain chem etch solution.
Laser ablate spray paint in the PCB trace inverse to expose the copper for etching.
Chem etch the PCB to isolate the traces.
Laser ablate the spray paint on the solder pads.


PCB Milling Operations


Milling operations are generated using pcb2gcode.  This is a command line program that reads information from configuration files.
pcb2gcode is called multiple times with different configuration files to generate the different G-code jobs (with different tools) required to machine out the PCB.


KiCAD

KiCAD Gerber export: disable the "Use extended X2 format" option.

PCB2GCODE


  
Alternate software: <![CDATA[]]>https://sourceforge.net/p/pygerber2gcode/code/ci/master/tree/<![CDATA[]]>



This tool worked great for generating G-code.


Much easier to use than FlatCAM.
Man page in file pcb2gcode.pdf.

Example config file: millproject
Generate code by running pcb2gcode in the same directory with millproject.
Use a short list of drill sizes, or it will use exact drill size for each part.  That can lead to a lot of tooling changes.
You can get some parameter by editing and running pcb_calcs.py.


The copper layer is very thin.  Got nice isolation with a margin of 0.5, could probably go lower.
This calcs the Z depth for drilling and edge cuts to cut into the tape.  It can be a bit tricky if you don't apply the height map.  Not clear if you can apply the height map to multiple files.

Bridges shouldn't be necessary if you don't cut too fast on the edge cuts.
Example call: <![CDATA[]]>https://gist.github.com/bullestock/87ed51aaadaae8b8d2f085756652eb04<![CDATA[]]>


Soldermask & Silkscreen

Intended process is to apply two layers of soldermask/ink to the PCB, then use my UV laser to ablate the areas that I don't want filled in.  Overall technique from: <![CDATA[]]>https://www.youtube.com/watch?v=NuJlgw7E7vg<![CDATA[]]>.

Soldermask & silkscreen cating goes down nicely with silkscreen netting & squeegee.


Use a squeegee to spread the ink.  I used Silicone squeegee from <![CDATA[]]>Amazon<![CDATA[]]>.
Cure with UV light.  I use a resin printer cure station for 3 min with board leaning against lamp.