added export to pm4n

scripts/Readme.md

@@ -57,7 +57,11 @@ nano millproject
 Run the export by providing the `.kicad_pcb` file as a first argument:
 
 ```bash
-./export.sh panel/Flow_Controller_Panel.kicad_pcb
+# Input layers/filenames and all milling/drilling parameters are taken from the config file: 'millproject'.
+docker run --rm -i -t \
+    -u "$(id -u):$(id -g)" \
+    -v "$(pwd):/data" \
+    ptodorov/pcb2gcode
 ```
 The script will first generate gerber files in the `gerbers` directory and then generate gcode files in the `gcode` directory.
 
@@ -75,5 +79,174 @@ Set up the entire back side as one big GND pour. Then, increase the thermal spok
 ![Thermal spoke width](../images/spoke_width.png)
 
 
+# MSLA PCB Exposure: KiCad → Photon Mono 4
 
+Convert KiCad PCB layers to `.pm4n` files for direct UV exposure on an **Anycubic Photon Mono 4** (9024×5120 px, 17 µm/px).
+
+---
+
+## Files
+
+| File | Purpose |
+|---|---|
+| `export.sh` | Main entry point — exports Gerbers from KiCad, converts to `.pm4n` |
+| `gerber_to_pm4n.py` | Python converter (Gerber → RLE → pm4n binary surgery) |
+| `Dummy.pm4n` | Template file for your specific printer. |
+
+---
+
+## Setup
+
+### 1. Create the Dummy.pm4n
+
+Open **CHITUBOX_Basic** slicer, select printer **Anycubic Photon Mono 4**, slice any tiny STL (a 1×1×0.05 mm box), and save as `Dummy.pm4n` in the same directory as `export.sh`.
+
+This file is reused for every job — it carries the correct LCD resolution metadata.
+
+### 2. Install dependencies
+
+```bash
+python3 -m venv .venv
+source .venv/bin/activate
+pip install pygerber Pillow numpy
+```
+
+Or activate the venv once and put `source .venv/bin/activate` in your shell profile.
+
+---
+
+## Usage
+
+```
+./export.sh [OPTIONS] <path/to/board.kicad_pcb>
+```
+
+### Options
+
+| Option | Default | Description |
+|---|---|---|
+| `--layers L,L,...` | `Front,F.Mask` | KiCad layer names to process |
+| `--invert L,L,...` | *(none)* | Layers to invert the image for |
+| `--mirror L,L,...` | *(none)* | Layers to mirror X for |
+| `--exposure N` | `60` | Exposure time in seconds |
+| `--dummy FILE` | `./Dummy.pm4n` | Path to dummy template |
+| `--out DIR` | `./output` | Output directory |
+| `--dpmm N` | `58.824` | Render resolution (native = 17 µm/px) |
+| `--pos X,Y` | centred | Board position in mm from top-left |
+
+---
+
+## Examples
+
+### Typical: top copper, positive-working resist (Bungard standard)
+
+```bash
+./export.sh \
+    --layers Front \
+    --invert Front \
+    --mirror Front \
+    --exposure 60 \
+    panel/Flow_Controller_Panel.kicad_pcb
+```
+
+`--invert`: Bungard presensitized is positive-working — UV removes resist, so the background must be exposed (white) and traces must block UV (dark). The Gerber is positive (copper=white), so inversion is needed.
+
+`--mirror`: the board sits copper-side-down on the FEP, so the image must be flipped so the pattern reads correctly through the board.
+
+### Multiple layers (e.g. copper + soldermask)
+
+```bash
+./export.sh \
+    --layers Front,F.Mask \
+    --invert Front,F.Mask \
+    --mirror Front,F.Mask \
+    --exposure 60 \
+    panel/Flow_Controller_Panel.kicad_pcb
+```
+
+### Quick test at lower resolution (faster render)
+
+```bash
+./export.sh --dpmm 30 --layers Front --invert Front --mirror Front panel/Flow_Controller_Panel.kicad_pcb
+```
+
+### Using gerber_to_pm4n.py directly
+
+```bash
+python3 gerber_to_pm4n.py Dummy.pm4n output/gerbers/Flow_Controller_Panel-Front.gbr \
+    --invert --mirror --exposure 60
+```
+
+---
+
+## Output structure
+
+```
+output/
+├── gerbers/
+│   ├── Flow_Controller_Panel-Front.gbr
+│   └── Flow_Controller_Panel-F_Mask.gbr
+└── pm4n/
+    ├── Flow_Controller_Panel-Front.pm4n          ← copy to USB, print on Mono 4
+    ├── Flow_Controller_Panel-Front.preview.png   ← visual check before printing
+    ├── Flow_Controller_Panel-F_Mask.pm4n
+    └── Flow_Controller_Panel-F_Mask.preview.png
+```
+
+---
+
+## Invert and mirror logic
+
+| Setting | When to use |
+|---|---|
+| `--invert` | Positive-working resist (standard Bungard): UV removes resist → background must be white (exposed), traces black (masked) |
+| no `--invert` | Negative-working resist: UV hardens resist → traces must be white |
+| `--mirror` | Board placed **copper-side down** on FEP (normal for this workflow) |
+| no `--mirror` | Board placed copper-side up |
+
+When in doubt: check the `.preview.png` before printing. Traces should appear **dark** on a white background for standard Bungard positive-working boards.
+
+---
+
+## Exposure calibration
+
+Start at **60 s** and bracket in ±15 s steps. Typical range for Bungard presensitized at 405 nm is 30–120 s depending on board age and storage conditions.
+
+A correctly exposed board after development will show:
+- Clear copper traces (resist intact, blue/green tint)
+- Bare copper in etched areas (resist removed, shiny copper)
+
+---
+
+## Troubleshooting
+
+**`kicad-cli: command not found`** — add KiCad to PATH:
+```bash
+export PATH="/usr/lib/kicad/bin:$PATH"
+```
+Or on Flatpak:
+```bash
+alias kicad-cli='flatpak run --command=kicad-cli org.kicad.KiCad'
+```
+
+**Expected Gerber not found** — KiCad's layer→filename mapping:
+
+| Layer | Filename stem |
+|---|---|
+| `F.Cu` | `Front` |
+| `B.Cu` | `Back` |
+| `F.Mask` | `F_Mask` |
+| `B.Mask` | `B_Mask` |
+| `F.SilkS` | `F_Silkscreen` |
+
+**Image looks wrong in preview** — check invert/mirror flags. Open `.preview.png`: for positive-working resist, traces = dark, background = white.
+
+**UVtools PCB Exposure freezes on per-item invert checkbox** — known v6 bug at 46 MP. Use the global invert checkbox at the bottom of the dialog instead, or use this script pipeline entirely.
+
+---
+First print checklist
+
+Open the `.pm4n` in Chitubox to visually verify before printing.
+Check the `.preview.png` — traces should appear black on white background (background = UV exposed = resist removed = etched away; traces = dark = resist kept = copper stays)
+Start with `--exposure 60` and bracket from there — Bungard presensitized at 405nm typically lands between 30–120s depending on board vintage and storage.