ROS × OctoPrint: G-code Streaming with Precise Pause for Mobile 3D Printing

The first-generation printer controller for a mobile additive-manufacturing platform, where a 3D printer rides on a mobile robot and has to pause whenever the robot moves. It streams G-code one line at a time to a Prusa printer through OctoPrint's REST API on a Raspberry Pi (OctoPi), and adds precise pause/resume, a pause-latency benchmark, robot-speed-based auto pause and real-time feed-rate override, all controllable from ROS.

Status: archived research code (Sep–Dec 2025). Development moved to direct USB control with Printrun in 3dprinter_control_PRINTRUN. That removes the HTTP round trip and allows line-level pause.

Architecture

flowchart LR
  ROBOT["Mobile robot<br/>/odom or /cmd_vel"] --> SPD["robot_speed_controller<br/>threshold + debounce"]
  SPD -->|"pause / resume"| GS["GCodeSender<br/>line-by-line, ok-acknowledged"]
  USER["Interactive CLI<br/>or ROS topics / services"] --> GS
  MOD["GCodeModifier<br/>F-value override"] -.->|"rewrites lines in the send stream"| GS
  GS -->|"HTTP POST /api/printer/command<br/>X-Api-Key"| OP["OctoPrint on Raspberry Pi"]
  OP -->|USB| PR["Prusa printer"]

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Development timeline

When	Module	What it adds
Sep 2025	gcode_controller.py, enhanced_gcode_sender*.py	Send G-code lines through the OctoPrint API from Python; interactive mode, batching, buffered reading, bed-heating wait
Oct 2025	accurate_pause_ver(last version).py	Precise pause system: per-line ok confirmation, printer-level pause/resume, Z-lift + filament retract on pause, temperature hold, state save/restore
Sep–Oct 2025	node示例/, gcode_controller_node/	ROS packaging: services start_print, pause_print, resume_print, stop_print, set_speed, get_status; messages PrintStatus, PrintProgress, TemperatureInfo; simple /gcode_command → /printer_status node
Oct–Nov 2025	PausePerformanceTest/	Pause-latency benchmark: pause at line N, at N %, or across files; repeats, mean / σ / min / max; JSON + CSV reports
Nov 2025	RobotMotionBasedControl/	Motion-based control: subscribe to robot speed (/odom or /cmd_vel), auto pause above a threshold and resume below it, debounce, CSV event log
Dec 2025	SpeedOverride/, gcode_modifier.py	Real-time feed-rate override: rewrite F values in the send stream (percentage or fixed), handling modal feed rates, without touching the file; inject custom G-code while paused

Results: pause / resume timing

Measured with PausePerformanceTest on an 854-line file, pausing at four points with three repeats each. Times are the end-to-end duration of the pause() / resume() routines, including the API calls, the Z-lift / retract moves and fixed settling waits.

Pause at	Pause mean ± σ	Resume mean ± σ
line 200 (23 %)	1014 ± 35 ms	2487 ± 221 ms
line 400 (47 %)	1133 ± 130 ms	2380 ± 53 ms
line 600 (70 %)	1256 ± 386 ms	2551 ± 327 ms
line 800 (94 %)	1033 ± 37 ms	2697 ± 308 ms

Pause time shows no clear trend with position in the file (median ≈1.03 s), but it has noticeable outliers. That, plus an HTTP round trip for every line, motivated the switch to direct serial control. Raw data: PausePerformanceTest/test_results/

Quick start

Requirements: a Raspberry Pi running OctoPrint (OctoPi) connected to the printer; Ubuntu + ROS 1 on the control PC; pip install requests.

1. In the OctoPrint web UI, open Settings → API / Application Keys and create a key.
2. Put the host and key in your local config: OCTOPRINT_URL / API_KEY near the bottom of the script you run, or the ~api_key ROS parameter for the nodes. Don't commit real keys.
3. Run the module you need:

# Precise-pause sender with an interactive prompt
python3 "accurate_pause_ver(last version).py"
#   >>> file /path/to/part.gcode   >>> pause   >>> resume   >>> status   >>> stop

# Printing + automatic pause when the robot moves
cd RobotMotionBasedControl && python3 script1112.py
#   >>> print /path/to/part.gcode   >>> threshold 0.04   >>> debounce 0.5   >>> status

# Speed override + G-code injection while paused
cd SpeedOverride && python3 gcode_sender12.3.py

Test models (STL) and sliced G-code files of four sizes (1 min to 2 h 48 min) are in stl files/ and PausePerformanceTest/test_files/.

Repository structure

├── accurate_pause_ver(last version).py   Precise-pause sender (latest OctoPrint version)
├── gcode_controller.py, enhanced_*.py    Early senders
├── gcode_modifier.py                     Feed-rate override module
├── gcode_controller_node/                Early ROS package (launch, config)
├── node示例/                              Full ROS package template: msg/, srv/, launch/, config/, test/
├── PausePerformanceTest/                 Latency benchmark framework, test G-code, results
├── RobotMotionBasedControl/              Speed-based auto pause + deployment/debug guides
├── SpeedOverride/                        Feed-rate override + G-code injection
├── config/printer_config.yaml            OctoPrint host, motion limits, G-code templates
├── demand_relevent/                      Requirements and stage plans (中文)
├── Notes/                                Usage notes (中文)
├── stl files/                            Test models
└── else/                                 Early tests and OctoPrint screenshots

Related repositories

Repo	Role
3dprinter_control_PRINTRUN	Next generation: ROS + Printrun over USB, line-level pause, override / inject
Octoprint	OctoPi setup and ROS packaging notes
KUKA-printer_munual	Lab manual for the KUKA + printer setup

Author

Huihang Liu · Computer Engineering, Penn State · @greenaandblue