Double-sided PCB milling

Configuring the project

Trailing Zeros

Eagle uses Trailing Zeros in its Excellon number format but does not properly report this format in the Excellon file. To tell FlatCAM to use this format by default set this system option excellon_zeros to T by using the set_sys command in the Shell Command Line Interface as shown below:

set_sys excellon_zero T

Note

2018-05-18 : Current Flatcam source is having problem with this command. If need this functionality, use stable version.

System unit

From options tab, select Units as mm.

Units: mm

Create mirror axis and alignment pins

Load Gerber files:

copper_top.gbr
copper_bottom.gbr
soldermask_top.gbr
soldermask_bottom.gbr
profile.gbr

Load Excellon file:

drills.xln

Mirror axis for bottom layer stuff, from menu bar, Tool -> Double-sided PCB Tool. Create mirror axis around Y axis at location x = 50 mm:

Mirror Axis: Y
Axis Location: Point
Point/Box: (50,0)

Mirror bottom layer objects one by one from the drop-down menu and click "Mirror Object":

copper_bottom.gbr
soldermask_bottom.gbr
profile.gbr
drills.xln

Alignment Holes help align the pcb when we flip it over. Create holes with 6 mm in diameter at desired locations. Then click "Create Alignment Drill":

Alignment Holes: (110, -5),(110, 60)
Drill diam: 6

You can generate gcode to cut Alignment Holes following similar process of the next section below. You can skip this for now and do it later.

Double-sided PCB Tool

Top-side non-copper area

Hide all other layer except copper_top.gbr. Select this object then navigate to "Non-copper regions" section and generate geometry:

Boundary Margin: 0.1

New geometry "copper_top.gbr_noncopper" is created. Navigate to "Paint Area" and generate paint area:

Tool dia:  0.1
Overlap:   0.05
Margin:    0.1
Method:    standard
Connect:   yes
Contour:   yes
Selection: All

New geometry "copper_top.gbr_noncopper_paint" is created. Navigate to "Create CNC Job" and generate toolpath:

Cut Z:        -0.05
Travel Z:      1.0
Feed Rate:     250.0
Tool dia:      0.1
Spindle speed: 24,000
Multi-Depth:   No

New geometry "copper_top.gbr_noncopper_paint_cnc" is created. Navigate to "Export G-Code" and export gcode.

Top-side isolation

Select "copper_top.gbr" and navigate to "Isolation Routing". Then generate geometry:

Tool dia:       0.145
Width(#passes): 1
Pass overlap:   0.0
Combine Passes: No

New geometry "copper_top.gbr_iso" is created. Navigate to "Create CNC Job" and generate toolpath:

Cut Z:        -0.05
Travel Z:      1.0
Feed Rate:     250.0
Tool dia:      0.145
Spindle speed: 24,000
Multi-Depth:   No

New geometry "copper_top.gbr_iso_cnc" is created. Navigate to "Export G-Code" and export gcode.

Top-side solder mask

Select "soldermask_top.gbr" and navigate to "Isolation Routing". Then generate geometry:

Tool dia:       0.0
Width(#passes): 1
Pass overlap:   0.0
Combine Passes: No

New geometry "soldermask_top.gbr_iso" is created. Navigate to "Paint Area" and generate paint area:

Tool dia:  0.1
Overlap:   0.05
Margin:    0.1
Method:    standard
Connect:   yes
Contour:   yes
Selection: All

New geometry "soldermask_top.gbr_iso_paint" is created. Navigate to "Create CNC Job" and generate toolpath:

Cut Z:        -0.05
Travel Z:      1.0
Feed Rate:     400.0
Tool dia:      0.1
Spindle speed: 24,000
Multi-Depth:   No

New geometry "soldermask_top.gbr_iso_paint_cnc" is created. Navigate to "Export G-Code" and export gcode. That's it for the top layer. Now flip over the PCB. The alignment holes helps keep PCB in correct position. The bottom-side non-copper area, isolation, soldermask are identical to the top layer.

Drilling

In drills.xln's Tools selection, choose hole sizes needed for drilling, excluding those large holes which need milling. Holes larger than 1 mm in diameter, I will use milling process instead. So select:

0.406
0.61
0.95
1.016

In Create CNC Job section:

Cut Z:        -1.95
Travel Z:      1.0
Feed Rate:     150.0
Tool change:   yes
Tool change Z: 50
Spindle speed: 24,000

New geometry "drills.xln_cnc" is created. Navigate to "Export G-Code" and export gcode. Next, select drills.xln again and choose hole sizes for milling:

2.2
3.2
3.302

At Mill Holes section, generate geometry:

Tool dia: 1.5

New geometry "soldermask_top.gbr_iso_paint" is created. Navigate to "Create CNC Job" and generate toolpath:

Cut Z:        -1.95
Travel Z:      1.0
Feed Rate:     150.0
Tool dia:      1.5
Spindle speed: 24,000
Multi-Depth:   yes
Depth/pass:    1

New geometry "drills.xln_mill_cnc" is created. Navigate to "Export G-Code" and export gcode.

Cutouts

This is a bit tricky. We need the cut edges pass right through the middle of profile lines. The measurement tool indicates 0.254 mm line thickness. For 1.5 mm tool dia, we set Tool dia = 1.5 - 0.254 mm. In Isolation Routing, generate geometry with the calculated Tool dia:

Tool dia:       1.246
Width(passes):  1
Pass overlap:   0.0
Combine Passes: No

New geometry "profile.gbr_iso" is created. Delete the interior part by Edit Geometry > Add Rectangle on inner line > With Select tool, press CTRL and select Geometry and box respectively > Cut Path > Delete Shape both box and inner line > Update Geometry.

Add Rectangle > Cut Path > Delete Shape

Only outter profile left.

For small size PCB, you might need tabs to hold PCB in place while cutting. To do so, edit geometry > draw boxes on where you want tabs> cut path > delete boxes. This PCB is big enough so I will move on to Create CNC Job. Note that Tool dia is 1.5 mm this time:

Cut Z:        -1.95
Travel Z:      1.0
Feed Rate:     150.0
Tool dia:      1.5
Spindle speed: 24,000
Multi-Depth:   yes
Depth/pass:    1

A closer look.

Cutting edges are on the middle of the profile.gbr's lines now.

New geometry "profile.gbr_iso_cnc" is created. Export G-Code. Now we are done with Flatcam.