Status 3D Printing Firmware Pipeline Hardware & docs

⚠️ Work in progress. This project is under active development — hardware wiring, firmware configuration and the software pipeline are all still changing, and some documents have drifted apart during past refactors. Known contradictions and errors are tracked in TODO.md ; inline TODO: markers in the docs point there. Expect updates.

This plotter draws vector graphics in G-code format using a pen. It is compatible with pens up to 11 mm in diameter, relies on inexpensive and widely available components, and uses a mostly 3D-printed frame with a few off-the-shelf mechanical parts. A set of test cases guides the user to verify the functionality of each hardware component before running GRBL.

The plotter's firmware is based on GRBL v1.1, which is a widely used open-source CNC controller firmware. It comes with a GUI toolset to transform images provided by the user to drawings in different styles via AI (technical drawing, pencil drawing, oil painting etc.) to send them to the plotter for drawing.

Assembly overview

• Overview
• Features
• Bill of Materials
• Assembly
• Electronics — see electronics.md for full details
• Firmware — see firmware/README.md for full details
• Testing & commissioning — see testing.md for the full procedure
• Software for host computer — see pipeline/README.md for full details
• Acknowledgements
• License

This pen plotter is meant for hobbyists and makers who want a low-cost machine to draw vector artwork on paper. It uses two stepper-driven axes, a simple pen carriage with a lift mechanism via solenoid for automated pen up/down control. Most structural parts are 3D-printed and a number of standard mechanical parts (rods, bearings, springs, belt and pulleys) complete the build.

• Compatible with pens up to 11 mm diameter
• Mostly 3D-printed components for easy reproduction
• Designed for A4-sized paper by default (adjustable)
• Open-source firmware based on GRBL v1.1
• Test suite to verify hardware functionality before running GRBL
• GUI toolset for image-to-G-code conversion with AI-based drawing styles (technical, pencil, oil painting etc.)

Below are the main 3D-printed parts and standard hardware used in the project. See the full BOM and the print/ directory for the source STL/PNG files and visual references.

Refer to the print/stl/ and print/png/ folders for all printable parts and preview images.

• frame_front.stl, frame_back.stl — frame halves
• housing_front.stl, housing_back.stl, housing_feet.stl — optional housing
• carriage_penholder_base.stl, carriage_penholder_connector_screw.stl — carriage and pen holder
• flat_steel_flange.stl, flat_steel_lever.stl — parts that interface with the steel pen-raising strip
• paper_bail_*.stl — paper bail and rollers
• paper_guide_front.stl, paper_guide_back.stl — paper gudie
• shaft_end_flange.stl, shaft_connector_flange.stl — shaft support parts
• solenoid_slider.stl — slider to make the pull solenoid a push solenoid (optional)
• cable_management.stl — optional cable management clips

• 12 mm square rods
• 6 mm round rods
• 12 mm steel shaft
• 2x 6mm linear ball bearings
• 2x NEMA 17 stepper motors
• 2GT 5mm timing belt, timing pulley and idler pulley
• Assorted M2/M3/M4 screws and nuts (details in original BOM)
• Bearings: F624ZZ bearings used in the rollers
• Springs: compression and extension springs as needed for pen lift and paper drive
• Pull solenoid 12 V (example: TAU-0530)

For a complete part list including quantities and McMaster/AliExpress references, see the original BOM in the repository.

The repository contains step-by-step photos and GIFs in print/zsb/ that show how parts fit together. The high-level assembly steps are:

1. Prepare the back frame: press in M3 nuts, install bearings, fit the timing-belt pulley and mount the optical endstop and solenoid.

2. Prepare the front frame: press in M3 nuts, install bearings, attach stepper motor and shaft coupler, and mount the drive pulley and endstop.

3. Join both frame halves: insert the paper guide rods, shaft, and the movable flat-steel strip used for pen lifting.

Fully assembled lever mechanism:

Fully assembled drive shaft:

4. Slide the carriage onto the guide rods and secure the timing belt to the carriage. Fit the belt around the drive and idler pulleys and tension appropriately.

Fully assembled carriage and timing belt mechanism:

5. Assemble and install the paper bail rollers and springs that hold and move the paper.

Detail for each paper bail roller:

Fully assembled paper bail:

6. Optionally assemble and attach the housing halves for a finished enclosure.

Important: some assembly steps (press-fitting nuts and bearings, re-threading printed holes) may require light machining or careful rework for reliable operation.

The electronics are intentionally simple: an Arduino Uno with a CNC Shield v3 and two A4988 stepper drivers. A solenoid controlled via a MOSFET handles pen lift.

For full details on wiring, pin mapping, microstepping, endstops and the solenoid circuit see electronics.md .

Assembly steps:

1. Route the stepper motor and endstop cables through the frame openings into the enclosure.
2. Secure cables with cable ties and cable management clips to avoid interference with moving parts.
3. Prepare the PCB holder by pressing in the M3 nuts. Screw the Arduino to it. Add the CNC Shield and the stepper drivers. Finally slide the PCB holder over the rods.
4. Assemble all wires according to electronics.md.
5. Attach the housing and fix it to the PCB holder and rods with M3 screws. Make sure the USB port and power jack are accessible.

The plotter runs GRBL v1.1 on the Arduino Uno. All firmware sources live in firmware/; GRBL is included as a Git submodule under firmware/grbl/.

For build instructions, flashing, GRBL parameter setup and G-code tooling see firmware/README.md .

Quick start:

git clone --recurse-submodules https://github.com/Smengerl/plotter.git
cd plotter/firmware
pio run -t upload # build and flash
pio device monitor # open serial console at 115200 baud

testing.md is the single source for the whole test and commissioning sequence — from the standalone hardware checks, through flashing GRBL, to a full end-to-end plot:

A set of CLI tools to send G-code files to the plotter is included in pipeline. The tool allows to configure individual processing pipelines by pure configuration without changing the code for images including adaptation of styles via prompt to a provided image, the necessary vectorization and sending the G-code.

A GUI frontend is provided for convenient usage of these mechanism including management of the raw images, applying various pipelines to them, previewing the adapted images and eventually sending the images to the plotter.

See pipeline/README.md for the full procedure.

The firmware is built on GRBL by Sungeun K. Jeon (Gnea Research LLC), Simen Svale Skogsrud and Jens Geisler. Thanks to the open-source community and the suppliers of affordable components. Third-party notices are collected in NOTICE.

Contributions are welcome.
See CONTRIBUTING.md for details and follow the CODE_OF_CONDUCT.md when contributing.

All .stl, .png and assembly pictures are automatically exported via my Fusion add-in, see here

This project is licensed per component — the parts have different origins and obligations:

Each area carries its own LICENSE file and, for firmware/, SPDX headers in the source. Third-party attributions: NOTICE.

• Simon Gerlach https://github.com/Smengerl

If something in this README is missing or unclear, please open an issue in the repository so the instructions can be improved.