GPX Wrapper for MakerBot Replicator 2

A Python post-processing wrapper for PrusaSlicer that automatically injects MakerBot Replicator 2-specific Start G-code and converts sliced G-code to Sailfish X3G binary format.

This wrapper is designed only for the MakerBot Replicator 2. It is not intended for other MakerBot models, even if this repository also contains additional GPX machine configuration files.

Overview

This wrapper script bridges PrusaSlicer and the GPX converter tool. It:

• Injects custom Start G-code optimized for MakerBot Replicator 2 (homing, heating, purge line)
• Converts G-code to X3G format using the GPX binary
• Manages file outputs automatically (replaces .gcode.pp with X3G binary, removes temporary files)
• Extracts nozzle temperature from G-code to apply in Start sequence
• Runs non-interactively for seamless PrusaSlicer integration

The wrapper logic in gpx_wrapper.py is currently specifically for the MakerBot Replicator 2 startup sequence and coordinates.

Features

• ✅ Marker-based G-code injection (safe, repeatable block replacement)
• ✅ Temperature extraction from first M104/M109 command
• ✅ Automatic removal of PrusaSlicer-generated .gcode files
• ✅ Graceful handling of already-converted files
• ✅ Full homing sequence using Sailfish endstop commands
• ✅ Optimized purge line for reliable first layer

Installation

1. Clone or download this repository to your local machine
2. Ensure GPX binary is present in the same directory as gpx_wrapper.py
3. Configure PrusaSlicer post-processing (see Usage section below)

Command Line

python gpx_wrapper.py "C:\path\to\file.gcode.pp"

PrusaSlicer Integration

1. Open PrusaSlicer → Preferences

2. Navigate to the Printer tab

3. Under G-code substitutions or Post-processing scripts, add:

   "<PATH_TO_PYTHON>\python.exe" "<PATH_TO_GPX_WRAPPER>\gpx_wrapper.py";

   Replace <PATH_TO_PYTHON> with your Python installation directory and <PATH_TO_GPX_WRAPPER> with the directory where gpx_wrapper.py is installed.

   PrusaSlicer automatically passes the generated file path to the script.

4. Configure output filename format:

   • In the Printer settings, set the Output filename format to:

     [input_filename_base].x3g

   • This ensures the final output file has the .x3g extension for MakerBot compatibility

5. After slicing, the script will:

   • Inject Start G-code
   • Convert to X3G binary
   • Replace the .gcode.pp file with the converted binary
   • Clean up temporary files

Script Behavior

Input

• Accepts .gcode.pp files from PrusaSlicer
• Expects G-code markers: GPX_START_MARKER and GPX_END_MARKER

Processing

1. Extracts nozzle temperature from first M104 or M109 command
2. Injects custom Start G-code sequence:
   • Full homing (XY to MAX, Z to MIN)
   • Origin calibration for Replicator 2
   • Nozzle heating
   • Extruder prime/purge line
3. Converts G-code to X3G format using GPX
4. Replaces input file with X3G binary

Output

• Modified .gcode.pp file (binary X3G format)
• Sibling .gcode file automatically removed (if present)
• Exit code: 0 (success) or 1 (error)

G-code Markers

The Start G-code block is bounded by markers:

; --- GPX_START_MARKER ---
; (Start G-code sequence here)
; --- GPX_END_MARKER ---

Important: Your G-code must include these markers for the wrapper to inject the Start sequence.

Start G-code Sequence

The injected Start sequence includes:

G162 X Y F3000       ; Home XY to MAX endstops
G161 Z F1200         ; Home Z to MIN endstop
G92 X285 Y152 Z0     ; Set origin for Replicator 2
G1 Z5 F1200          ; Lift Z slightly
M104 S[temp]         ; Set nozzle temperature
M6 T0                ; Wait for nozzle temperature
G92 E0               ; Reset extruder
G1 X5 Y5 F3000       ; Move to purge start
G1 E8 F200           ; Extrude
G1 X120 F3000        ; Draw purge line

Temperature Extraction

The script extracts the first nozzle temperature from:

• M104 S<temperature> (set nozzle temp, no wait)
• M109 S<temperature> (set nozzle temp, wait)

If no temperature command is found, it defaults to 200°C.

File Structure

.
├── gpx_wrapper.py           # Python post-processing script
├── gpx.exe                  # GPX converter binary (v2.6.8)
├── tests/                   # Python tests
├── examples/                # Example G-code and configurations
│   ├── example-machine.ini
│   ├── example-pause-at-zpos.ini
│   ├── example-temperature.ini
│   ├── gpx.ini
│   └── macro-example.gcode
├── machine_inis/            # Machine-specific configurations
│   ├── r2.ini               # MakerBot Replicator 2 config
│   ├── r2h.ini              # Replicator 2 w/ Heated Build Plate
│   ├── c3.ini               # Replicator 2 Copybot 3D
│   └── (other machines)
└── scripts/                 # Utility scripts
    ├── gpx.py
    └── s3g-decompiler.py

Machine Configurations

This repository includes INI files for various MakerBot printers:

These GPX configuration files are provided for reference, but the wrapper script itself currently supports only the MakerBot Replicator 2.

• r2.ini - MakerBot Replicator 2
• r2h.ini - Replicator 2 with Heated Build Plate
• r2x.ini - Replicator 2X
• r2d.ini - Replicator 2 Dual Extruder
• c3.ini, c4.ini - Replicator Copybot models
• cp4.ini, cpp.ini - Replicator Compact models
• t6.ini, t7.ini - Thingomatic models
• z.ini - CupCake CNC
• And more...

Troubleshooting

Error: "Unable to find GPX"

• Ensure gpx.exe is in the same directory as gpx_wrapper.py
• Check that the file name is exactly gpx.exe

Error: "GPX markers not found"

• Your G-code file is likely already converted (binary X3G format)
• The script will skip injection and output will remain unchanged

Error: "Unable to inject Start G-code"

• Verify that your G-code template includes:

  ; --- GPX_START_MARKER ---
  ; --- GPX_END_MARKER ---

Script runs but no file is created

• Check PrusaSlicer output path configuration
• Verify file permissions in the output directory

Requirements

• Python 3.10+ (for gpx_wrapper.py)
• GPX binary (v2.6.8 included)
• .NET Framework 4.5+ (for GPX)
• PrusaSlicer 2.9.4 (tested for integration)

Credits

This project uses the GPX converter originally developed by:

• markwal/GPX - GPX conversion library and CLI tool
  • Original GPX converter for MakerBot 3D printers
  • Supports Sailfish firmware and S3G/X3G binary formats
  • Licensed under GPLv2

Special thanks to the MakerBot community and Sailfish firmware developers for maintaining support for legacy printers.

License

This wrapper script and configurations are provided as-is. The GPX binary is subject to its original license. See the GPX repository for licensing details.

Support

For issues specific to:

• GPX converter: See github.com/markwal/GPX
• PrusaSlicer: See prusa3d.com/prusaslicer
• This wrapper: Open an issue on this repository

Changelog

v1.0.0 (Initial Release)

• ✅ Basic G-code injection and GPX conversion
• ✅ Temperature extraction from G-code
• ✅ PrusaSlicer post-processing integration
• ✅ Sibling .gcode file cleanup
• ✅ Graceful error handling
• ✅ English localization

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Last Updated: April 2026 Tested On: MakerBot Replicator 2, Sailfish 7.7, PrusaSlicer 2.9.4