.FX File Format

A .fx file is Flux’s native save format for a single part. This document describes exactly what the file contains, how each piece is encoded, and how to read it from outside Flux.

Entry point: Core/Part/Part.cs — method Part.SaveFX(Stream stm, ESaveFX flags)

1. Container: ZIP Archive

A .fx file is a standard ZIP archive (PKZIP format). You can open it with any ZIP tool (unzip, 7-Zip, Python zipfile, MATLAB unzip). The archive contains several named entries:

Entry name Encoding Content

Entry name	Encoding	Content
`Summary`	UTF-8 text	Human-readable key/value summary of the part
`Thumbnail`	PNG image	256 × 256 preview rendered at save time
`MMF2D`	MMF format	2D drawing (only written when `ESaveFX.MMF` flag is set)
`Attachments/…`	Varies	External files attached to the part
`Data\Info`	AU object	`PartInfo` — name, material, thickness, GUID, etc.
`Data\Version`	AU object	`VersionInfo` — Flux build number and revision
`Data\Dwg`	AU object	`Drawing2` — all 2D flat geometry (plines, bend marks, …)
`Data\SurfaceModel`	AU object	Surface model (only if no 3D model, or in diagnostic mode)
`Data\Model`	AU object	`Model3` — 3D folded model
`Data\FoldTech`	AU object	`FoldTech` — bend sequence and fold parameters
`Data\Misc`	AU object	`MiscData` dictionary (miscellaneous key/value pairs)
`Data\BendTech`	AU object	`BendTech` — press-brake tooling
`Data\CellTech`	AU object	`BCellTech` — bending cell data
`Data\CutTech`	AU object	`FlatTech[]` — laser tooling: `[CutTech, Layout]`
`Plugin\<name>\<key>`	Raw bytes	Custom data written by plugin hooks
`Geo\<srcfilename>`	Raw bytes	Source geometry for bevel cutting

Summary

UTF-8 text

Human-readable key/value summary of the part

Thumbnail

PNG image

256 × 256 preview rendered at save time

MMF2D

MMF format

2D drawing (only written when ESaveFX.MMF flag is set)

Attachments/…

Varies

External files attached to the part

Data\Info

AU object

PartInfo — name, material, thickness, GUID, etc.

Data\Version

AU object

VersionInfo — Flux build number and revision

Data\Dwg

AU object

Drawing2 — all 2D flat geometry (plines, bend marks, …)

Data\SurfaceModel

AU object

Surface model (only if no 3D model, or in diagnostic mode)

Data\Model

AU object

Model3 — 3D folded model

Data\FoldTech

AU object

FoldTech — bend sequence and fold parameters

Data\Misc

AU object

MiscData dictionary (miscellaneous key/value pairs)

Data\BendTech

AU object

BendTech — press-brake tooling

Data\CellTech

AU object

BCellTech — bending cell data

Data\CutTech

AU object

FlatTech[] — laser tooling: [CutTech, Layout]

Plugin\<name>\<key>

Raw bytes

Custom data written by plugin hooks

Geo\<srcfilename>

Raw bytes

Source geometry for bevel cutting

Not all entries are always present:

Data\Model is absent if the part was imported as a flat DXF.
Data\CutTech is absent if no laser tooling has been run.
Thumbnail is absent when ESaveFX.NoThumbnail is set (e.g. in batch nesting).
MMF2D is only written when ESaveFX.MMF is explicitly requested.

2. The Summary Entry

Summary is a plain UTF-8 text file with INI-style sections. It is written by Part.SaveSummary() (calling PartInfo.SaveSummary(), then each tech’s SaveSummary()).

2.1. [Basic] Section

Always present. Contains the human-readable part metadata:

[Basic]
Name=Bracket-Left
MatlName=1.0038
Thickness=1.5
Weight=0.42
Comments=optional free text
Guid=3f2a1b00-4c5d-6e7f-8a9b-0c1d2e3f4050
Bound2=(-50,-30)-(80,60)
Bound3=(-50,-30,-3)-(80,60,3)

Bound2 is the axis-aligned bounding box of the flat drawing in mm. Bound3 is the bounding box of the 3D folded model. Both are written only if the corresponding object exists.

2.2. [BendTech], [FoldTech], [CutTech] Sections

Written by the respective technology objects when present. Their content varies but follows the same Key=Value style.

3. The Thumbnail Entry

Thumbnail is a raw PNG file (RFC 2083). You can write it directly to disk and open it as any image. It is a 256 × 256 RGBA image rendered from the part’s flat drawing.

There is no extra header — the entry’s bytes are the PNG file directly (starting with the PNG magic bytes 89 50 4E 47 0D 0A 1A 0A).

4. AU Object Entries (Data\*)

All Data\* entries use the AU object format — Flux’s binary serialization system. The code lives in Base/IO/ByteStm.cs and Base/Gold/AuStream.cs.

4.1. Wrapper Header (written by `AddObject`)

File: Core/Extension.cs:356

Every AU entry starts with an 8-byte wrapper before the actual AU payload:

Offset Size Value

Offset	Size	Value
0	4 bytes	Magic: `0xA1 0x08 0xDE 0x4B` (little-endian `0x4BDE08A1`)
4	4 bytes	Payload length in bytes (little-endian `int32`)
8	N bytes	AU payload (see below)

4 bytes

Magic: 0xA1 0x08 0xDE 0x4B (little-endian 0x4BDE08A1)

4 bytes

Payload length in bytes (little-endian int32)

N bytes

AU payload (see below)

// From Extension.cs — AddObject writes exactly:
stream.Write(OBJSTREAM);          // 0x4BDE08A1 as int32 LE
stream.Write(bytes.Data.Length);  // int32 LE
stream.Write(bytes.Data, 0, bytes.Data.Length);

4.2. AU Payload Header

File: Base/Gold/AuStream.cs:374

The AU payload starts with:

Offset Size Value

Offset	Size	Value
0	4 bytes	AU signature: `0x3D 0x2D 0x6F 0x1A` (little-endian `0x1A6F2D3D`)
4	1 byte	AU format version (currently `5`)
5	…	Type table + object graph (see below)

4 bytes

AU signature: 0x3D 0x2D 0x6F 0x1A (little-endian 0x1A6F2D3D)

1 byte

AU format version (currently 5)

…

Type table + object graph (see below)

mStm.WriteInt32(mSign);    // 0x1A6F2D3D
mStm.WriteByte(AuVersion); // 5
WriteObj(mObj, null);
Write(EToken.Epilogue);    // byte 11
mStm.WriteIntV(objCount);
mStm.WriteString("EOF");

.FX File Format

1. Container: ZIP Archive

2. The Summary Entry

2.1. [Basic] Section

2.2. [BendTech], [FoldTech], [CutTech] Sections

3. The Thumbnail Entry

4. AU Object Entries (Data\*)

4.1. Wrapper Header (written by AddObject)

4.2. AU Payload Header

4.1. Wrapper Header (written by `AddObject`)