144 lines
4.4 KiB
Markdown
144 lines
4.4 KiB
Markdown
# KiCad → Stencil G-code pipeline
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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.
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---
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## Prerequisites
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- Ubuntu 24.04
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- Python 3.10–3.12
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- KiCad v9
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- A flat end mill (corn bit), 0.5 mm recommended
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---
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## Installation
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### 1. System dependencies
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```bash
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sudo apt install python3-venv python3-pip libgeos-dev libspatialindex-dev libxcb-cursor0
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```
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### 2. Clone FlatCAM beta 8.995
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```bash
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git clone --branch mstanciu_Beta_8.995 --depth 1 https://github.com/dwrobel/flatcam.git flatcam-beta
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```
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### 3. Create a Python venv and install dependencies
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```bash
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cd flatcam-beta
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python3 -m venv .flatcam-env
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source .flatcam-env/bin/activate
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pip install PyQt6 PyQt6-Qt6 PyQt6-sip
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# Skip ortools (path optimizer), rasterio, and gdal (image import) — not needed for stencils
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grep -vE "ortools|rasterio|gdal" requirements.txt | pip install -r /dev/stdin
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```
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### 4. Verify
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```bash
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python flatcam.py --version
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```
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You should see the FlatCAM version string printed without errors.
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Go back to the project directory:
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```bash
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cd ..
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```
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### 5. Export the stencil gerbers
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Export the gerber layers `F.Paste` and `B.Paste`
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```bash
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kicad-cli pcb export gerbers -o gerbers -l F.Paste,B.Paste ../kicad2panel/panel/Flow_Controller_Panel.kicad_pcb
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```
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---
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## Usage
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Generate the stencil G-code for both layers:
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```bash
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./run_stencil.sh gerbers/Flow_Controller_Panel-F_Paste.gtp \
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gcode/Flow_Controller_Panel-F_Paste-stencil.nc
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./run_stencil.sh gerbers/Flow_Controller_Panel-B_Paste.gbp \
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gcode/Flow_Controller_Panel-B_Paste-stencil.nc
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```
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G-code for both layers should be in:
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```
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gcode/Flow_Controller_Panel-F_Paste-stencil.nc
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gcode/Flow_Controller_Panel-B_Paste-stencil.nc
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```
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---
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## Parameters
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All cutting parameters are at the top of `paste_stencil.tcl`:
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| Variable | Default | Description |
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| `TOOL_DIA` | `0.5` | End mill diameter in mm |
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| `CUT_Z` | `-0.2` | Cutting depth in mm (negative). Set slightly past material thickness |
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| `TRAVEL_Z` | `2.0` | Safe travel height in mm |
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| `FEEDRATE` | `120` | XY feed rate in mm/min |
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| `SPINDLE` | `15000` | Spindle speed in RPM |
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| `OVERLAP` | `60` | Tool overlap in % — higher = cleaner clearing, more paths |
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| `MARGIN` | `0.0` | Inset from aperture edge in mm. 0 = cut to exact pad size |
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### Depth by material
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| Material | Thickness | `CUT_Z` | `SPINDLE` | `FEEDRATE` |
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|---|---|---|---|---|
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| Brass shim (CW614N) | 0.15 mm | -0.18 | 24000 RPM | 120 mm/min |
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| Polyimide (Kapton) | 0.10 mm | -0.13 | 24000 RPM | 300 mm/min |
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| Stainless steel shim | 0.15 mm | -0.18 | 16000 RPM | 60 mm/min |
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---
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## Preprocessor
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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.
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Alternative: `GRBL_11_no_M6` suppresses tool change commands — not needed for a single-tool stencil job but harmless either way.
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---
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## Workholding notes
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- Stencil material is thin and will flex — use double-sided tape on a flat spoilboard
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- Zero Z directly on the stencil surface, not the spoilboard
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- For brass shim, clamp the edges with small clips if the tape isn't holding — chatter from an unanchored sheet ruins aperture quality
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---
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## Troubleshooting
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**FlatCAM hangs after writing G-code**
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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.
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**`ImportError: cannot import name 'Inf' from numpy`**
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You have the old PyPI FlatCAM 8.5 installed. Follow the installation steps above to switch to the beta 8.995 clone.
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**`ImportError: cannot import name 'cascaded_union' from shapely.ops`**
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Same cause — old FlatCAM 8.5 is incompatible with Shapely 2.0. Switch to beta 8.995.
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**G-code cuts everything except the pads**
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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.
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**`gdal` fails to install**
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Skip it — `gdal` is only needed for the image import plugin. Use:
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```bash
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grep -vE "ortools|rasterio|gdal" requirements.txt | pip install -r /dev/stdin
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``` |