# KiCad → Stencil G-code pipeline

Automates the conversion of a KiCad v9 `F.Paste` and `B.Paste` Gerber to G-code for CNC milling a solder paste stencil, using FlatCAM beta 8.995 headless. Tested on Ubuntu 24.04 with Python 3.12 and a Frezu 3040 / FluidNC controller.

This project shares a single FlatCAM install (`~/flatcam-beta`) with other `kicad2*` pipelines (e.g. `kicad2outlines`). Install FlatCAM once; each project just points to it.

---

## Prerequisites

- Ubuntu 24.04
- Python 3.10–3.12
- KiCad v9
- A flat end mill (corn bit), 0.5 mm recommended

---

## Installation

### 1. System dependencies

```bash
sudo apt install python3-venv python3-pip libgeos-dev libspatialindex-dev libxcb-cursor0
```

### 2. Install FlatCAM beta 8.995 (shared, once)

If `~/flatcam-beta` already exists, skip to step 3 — there's nothing to do here.

```bash
git clone --branch mstanciu_Beta_8.995 --depth 1 https://github.com/dwrobel/flatcam.git ~/flatcam-beta

cd ~/flatcam-beta
python3 -m venv .flatcam-env
source .flatcam-env/bin/activate

pip install PyQt6 PyQt6-Qt6 PyQt6-sip

# Skip ortools (path optimizer), rasterio, and gdal (image import) — not needed for stencils/outlines
grep -vE "ortools|rasterio|gdal" requirements.txt | pip install -r /dev/stdin

deactivate
```

### 3. Verify

```bash
~/flatcam-beta/.flatcam-env/bin/python ~/flatcam-beta/flatcam.py --version
```

You should see the FlatCAM version string printed without errors.

### 4. Point this project at the shared install

`run_stencil.sh` reads the `FLATCAM_HOME` environment variable, defaulting to `~/flatcam-beta` if unset. Override it only if your install lives elsewhere:

```bash
export FLATCAM_HOME=~/flatcam-beta   # default, usually no need to set this
```

### 5. Export the stencil gerbers

Export the gerber layers `F.Paste` and `B.Paste`
```bash
kicad-cli pcb export gerbers -o gerbers -l F.Paste,B.Paste ../kicad2panel/panel/Flow_Controller_Panel.kicad_pcb
```

---

## Usage

Generate the stencil G-code for the layer `F.Paste`:
```bash
./run_stencil.sh gerbers/Flow_Controller_Panel-F_Paste.gtp \
                 gcode/Flow_Controller_Panel-F_Paste-stencil.nc
```

It should output:

```
→ Running FlatCAM headless...
  Gerber : gerbers/Flow_Controller_Panel-F_Paste.gtp
  Output : gcode/Flow_Controller_Panel-F_Paste-stencil.nc



✓ Done: gcode/Flow_Controller_Panel-F_Paste-stencil.nc (277 lines)
```

Generate the stencil G-code for the layer `B.Paste`:
```bash
./run_stencil.sh gerbers/Flow_Controller_Panel-B_Paste.gbp \
                 gcode/Flow_Controller_Panel-B_Paste-stencil.nc
```

It should output:

```
→ Running FlatCAM headless...
  Gerber : gerbers/Flow_Controller_Panel-B_Paste.gbp
  Output : gcode/Flow_Controller_Panel-B_Paste-stencil.nc



✓ Done: gcode/Flow_Controller_Panel-B_Paste-stencil.nc (1895 lines)
```
---

## Parameters

All cutting parameters are at the top of `paste_stencil.tcl`:

| Variable | Default | Description |
|---|---|---|
| `TOOL_DIA` | `0.5` | End mill diameter in mm |
| `CUT_Z` | `-0.2` | Cutting depth in mm (negative). Set slightly past material thickness |
| `TRAVEL_Z` | `2.0` | Safe travel height in mm |
| `FEEDRATE` | `120` | XY feed rate in mm/min |
| `SPINDLE` | `24000` | Spindle speed in RPM |
| `OVERLAP` | `60` | Tool overlap in % — higher = cleaner clearing, more paths |
| `MARGIN` | `0.0` | Inset from aperture edge in mm. 0 = cut to exact pad size |

### Depth by material

| Material | Thickness | `CUT_Z` | `SPINDLE` | `FEEDRATE` |
|---|---|---|---|---|
| Brass shim (CW614N) | 0.15 mm | -0.18 | 24000 RPM | 120 mm/min |
| Polyimide (Kapton) | 0.10 mm | -0.13 | 24000 RPM | 300 mm/min |
| Stainless steel shim | 0.15 mm | -0.18 | 16000 RPM | 60 mm/min |

---

## Preprocessor

The script uses the `GRBL_11` preprocessor (`-pp GRBL_11` in `paste_stencil.tcl`), which produces grbl 1.1 compatible G-code. FluidNC implements the grbl protocol so this works directly with no modifications.

Alternative: `GRBL_11_no_M6` suppresses tool change commands — not needed for a single-tool stencil job but harmless either way.

---

## Workholding notes

- Stencil material is thin and will flex — use double-sided tape on a flat spoilboard
- Zero Z directly on the stencil surface, not the spoilboard
- For brass shim, clamp the edges with small clips if the tape isn't holding — chatter from an unanchored sheet ruins aperture quality

---

## Troubleshooting

**FlatCAM hangs after writing G-code**
The `run_stencil.sh` wrapper detects the `TclCommandQuit` log line and kills the process after 3 seconds. This is expected behavior — FlatCAM's Qt GUI cleanup hangs in headless mode.

**`ImportError: cannot import name 'Inf' from numpy`**
You have the old PyPI FlatCAM 8.5 installed somewhere on your `PATH`/venv. Make sure `FLATCAM_HOME` points at `~/flatcam-beta` (the beta 8.995 clone from the install steps above), not a pip-installed FlatCAM.

**`ImportError: cannot import name 'cascaded_union' from shapely.ops`**
Same cause — old FlatCAM 8.5 is incompatible with Shapely 2.0. Check `FLATCAM_HOME` as above.

**G-code cuts everything except the pads**
You used `ncc` (non-copper clear) instead of `paint`. The correct command is `paint` — it pockets the pad polygons. `ncc` clears everything around them, which is the inverse.

**`gdal` fails to install**
Skip it — `gdal` is only needed for the image import plugin. Use:
```bash
grep -vE "ortools|rasterio|gdal" requirements.txt | pip install -r /dev/stdin
```

**Multiple projects, which one owns the FlatCAM install?**
None of them — `~/flatcam-beta` is shared and project-agnostic. Install it once via any one project's instructions above; every other `kicad2*` project just needs `FLATCAM_HOME` set (or left at its default) to find it. Don't `git clone` a second copy per project.