# Busbar Designer + Hex Holder Designer

Web "combine" for cylindrical-cell battery pack production. Two pages:

| Page        | Purpose                                                                  |
|-------------|---------------------------------------------------------------------------|
| `/holder`   | Parametric **hex cell holder** designer — adjust pack size / cell type, see 3D, download STL for printing. |
| `/`         | **Busbar** designer — import cell coordinates, group into busbars (parallel + series), export STEP/DXF/SVG for laser cutting. |

The holder page has a **Design busbars →** button that auto-creates a busbar project pre-loaded with the exact cell coordinates from the configured holder.

---

Web tool for designing nickel/copper **busbars** over cylindrical-cell battery packs (21700, 18650, ...) built with hex-shaped cell holders.

Workflow:
1. Import cell-center coordinates (paste from OpenSCAD console, CSV, JSON — or generate from `cell_dia / wall / rows / cols`).
2. View cells on a 2D canvas at real mm scale.
3. Click cells to select; group selected cells into named **busbars** (parallel groups), then chain busbars in series.
4. Each busbar is drawn as a strip of configurable width with circular pads + welding-window holes over each cell center.
5. Export busbar geometry to **STEP** (mandatory), plus **DXF** and **SVG** for laser/waterjet cutting.

## Quick start

Requires **Python 3.10+** and **OpenSCAD** on the host (only needed for the `/holder` page; the busbar page works without it).

```powershell
# Windows / PowerShell
cd busbar-designer
python -m venv .venv
.\.venv\Scripts\Activate.ps1
pip install -r requirements.txt
python app.py
```

OpenSCAD install: Windows — `winget install OpenSCAD.OpenSCAD`; Linux — `apt install openscad`.

Then open <http://localhost:5000> for the busbar designer, or <http://localhost:5000/holder> for the hex holder designer.

> First-time install pulls **build123d** (~ 200 MB; bundles OpenCASCADE via OCP) and may take several minutes.

### Linux / macOS

```bash
cd busbar-designer
python3 -m venv .venv
source .venv/bin/activate
pip install -r requirements.txt
python app.py
```

## Geometry source of truth

All cell-center math matches Addy's `Hex-Cell-Holder/hex_cell.scad`:

| Variable        | Formula                                  | 21700 default |
|-----------------|------------------------------------------|---------------|
| `hex_w`         | `cell_dia + 2*wall`                      | `22.8 mm`     |
| `hex_pt`        | `hex_w / 2 / cos(30°)`                   | `13.164 mm`   |
| `opening_dia`   | `cell_dia − 2*cell_top_overlap`          | `15.2 mm`     |
| row pitch (Y)   | `1.5 * hex_pt`                           | `19.746 mm`   |
| col pitch (X)   | `hex_w`                                  | `22.8 mm`     |
| `rect` row shift | `0` (even) / `0.5*hex_w` (odd)         | `11.4 mm`     |

## Import formats

The importer auto-detects:

- **OpenSCAD ECHO**: `ECHO: "Cell 1: x = 0.0, y = 0.0"` (paste straight from console).
  - If your `hex_cell.scad` doesn't print these, drop `scad_snippet.scad` (in this repo) at the bottom of the file.
- **CSV**: `index,x,y` (header optional).
- **JSON**: `[{"id":1,"x":0,"y":0}, ...]` or `[[x,y], ...]`.
- **Generator** tab: enter `cell_dia / wall / rows / cols / pack_style` — coordinates are computed with the exact OpenSCAD formulas.

## Persistence

State is stored in a SQLite file (`data/busbar.db` by default; override with `BUSBAR_DB` env var):

| Table       | What                                                                  |
|-------------|------------------------------------------------------------------------|
| `projects`  | Full editor state (cells + busbars + params) per project              |
| `presets`   | Named param bundles you save from the params panel                    |
| `snapshots` | Auto-history per project; max `SNAPSHOT_RETENTION` (default 20) kept  |

**REST API** (all JSON):

| Method | Path                                          | What                          |
|--------|-----------------------------------------------|-------------------------------|
| GET    | `/api/projects`                               | list projects                 |
| POST   | `/api/projects`                               | create `{name, data}`         |
| GET    | `/api/projects/{id}`                          | full project                  |
| PUT    | `/api/projects/{id}`                          | update `{name?, data?, snapshot?, note?}` |
| DELETE | `/api/projects/{id}`                          | delete (cascades to snapshots) |
| GET    | `/api/projects/{id}/snapshots`                | list snapshots                |
| GET    | `/api/snapshots/{sid}`                        | full snapshot                 |
| POST   | `/api/snapshots/{sid}/restore`                | roll project back             |
| GET    | `/api/presets`                                | list presets                  |
| POST   | `/api/presets`                                | create `{name, params}`       |
| PUT    | `/api/presets/{id}`                           | update                        |
| DELETE | `/api/presets/{id}`                           | delete                        |

**UI behaviour**:
- Active project ID is in the URL: `?p=42`. Bookmark or open from another device → same state.
- Auto-save fires 1.5 s after the last change. The first save in any 60 s window also creates a history snapshot.
- "History" button shows the snapshot list with a Restore action.
- Presets are saved server-side and apply to any project with one click.

**Backup**: the entire DB is one file. Copy `data/busbar.db` (or the `data/` folder in Docker) for offline backup.

## Export

| Format | Use                                         | Backend                  |
|--------|---------------------------------------------|--------------------------|
| STEP   | CAD (FreeCAD, Fusion, SolidWorks)           | `build123d` → OpenCASCADE |
| DXF    | Laser cutter / CNC (2D)                     | `build123d` → ezdxf      |
| SVG    | Quick preview, illustrator                  | `build123d`              |

STEP files are written as **flat 3D faces** (not solids) so a fab shop can lay them out before cutting. If you need a thick solid (e.g., 0.2 mm nickel) toggle "Extrude busbars" — the backend will extrude each strip to the configured thickness.

## Project layout

```
busbar-designer/
├── app.py                 # Flask server: static files + /api/export/{step,dxf,svg}
├── busbar_export.py       # build123d → STEP / DXF / SVG
├── requirements.txt
├── scad_snippet.scad      # paste into hex_cell.scad to echo per-cell coordinates
├── CLAUDE.md              # architecture notes for Claude / future contributors
├── tests/
│   └── test_export.py
└── static/
    ├── index.html
    ├── styles.css
    └── js/
        ├── app.js
        ├── importer.js
        ├── viewport.js
        ├── groups.js
        ├── geometry.js
        └── exporter.js
```

## Deploy to a home server

### Recommended: manual LXC + `install.sh`

1. **Create LXC in Proxmox web UI** — Debian 12 standard template, unprivileged, 4 cores / 8 GB RAM / 32 GB disk, network DHCP. Enable `Features → nesting=1`.
2. **Inside the LXC** (`pct enter <CTID>` from the host):
   ```bash
   REPO_URL=https://gitea.example.com/me/busbar-designer.git \
   bash -c "$(curl -fsSL https://gitea.example.com/me/busbar-designer/raw/branch/main/deploy/install.sh)"
   ```
3. Open `http://<lxc-ip>:5000` from any device on your LAN.

Update after `git push` to your Gitea:
```bash
pct exec <CTID> -- bash /opt/busbar-designer/deploy/update.sh
```

See [`deploy/README.md`](deploy/README.md) for backup/restore, troubleshooting, and what `install.sh` actually installs.

### Alternative: Docker

```bash
git clone <repo> busbar-designer && cd busbar-designer
mkdir -p data
docker compose up -d --build
```

`data/` is bind-mounted at `/app/data` so the SQLite DB survives `docker compose down`.

### Reverse proxy (optional)

If you want it behind your existing nginx / Caddy / Traefik:

```nginx
location / {
    proxy_pass         http://127.0.0.1:5000;
    proxy_set_header   Host $host;
    proxy_set_header   X-Forwarded-For $remote_addr;
    proxy_read_timeout 120s;   # STEP export can take a few seconds
    client_max_body_size 5m;
}
```

For Caddy:

```
busbar.example.com {
    reverse_proxy 127.0.0.1:5000
}
```

### Security

The app has no authentication. Either:
- expose only on your LAN (default), or
- put it behind an authenticating reverse proxy (Caddy `basic_auth`, Authelia, Pocket-ID, etc.).

## Troubleshooting

- **`pip install build123d` fails on Windows / Python 3.13** — the prebuilt OCP wheels lag the latest Python release. If your `python --version` is 3.13, install Python 3.12 from python.org and use it for the venv: `py -3.12 -m venv .venv`.
- **STEP opens empty in FreeCAD** — make sure at least one busbar exists and contains ≥ 1 cell. The exporter writes only assigned busbars.
- **Port 5000 in use** — set `PORT=5050 python app.py`.

## License

MIT.