Chitrakaar

2D CNC Pen Plotter

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Overview

Chitrakaar is a belt-driven 2D CNC pen plotter that autonomously reproduces digital images on paper. The system extracts edges from an input image, converts them into G-code toolpaths, and executes them via an Arduino-based motion controller driving two stepper motors and a servo-actuated pen lift mechanism.

Input Image → MATLAB (G-code) → Python (Serial) → Arduino (Motion) → Paper

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Hardware

Component	Specification
Microcontroller	Arduino Uno R4
Motor Shield	CNC Shield V3
Stepper Drivers	A4988 × 2
Stepper Motors	NEMA 17 × 2
Servo Motor	Standard PWM servo
Linear Motion	8mm chrome-steel rods + LM8UU bearings
Drive Mechanism	Timing belt and pulley
Pen Lift	Servo-actuated rack and pinion
Power Supply	12V DC adapter

Full bill of materials: 2d-Printer List of Items.csv

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Mechanical Design

The frame uses chrome-plated carbon-steel smooth rods on a rigid rectangular base. X and Y axes use LM8UU linear bearings riding on 8mm guide rods, driven by NEMA 17 steppers via timing belts. The Z-axis pen lift is achieved through a servo motor coupled to a rack-and-pinion mechanism, converting angular displacement into precise vertical pen motion. The drawing surface remains stationary throughout operation.

CAD files: 3d_Parts/

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Electronics

The CNC Shield V3 mounts directly onto the Arduino Uno R4. A4988 drivers are seated in the X and Y slots. The servo connects to the onboard Pin 11 servo header on the shield.

Detailed wiring reference: Circuits_and_Code/Connections.txt

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Physical Build

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Software Pipeline

1. G-code Generation - MATLAB

File: Image_to_GCode/ImagetoGCodeConverter.m

Processes an input image into a .gcode toolpath file. Performs binary thresholding, manual edge detection, nearest-neighbour path ordering, coordinate scaling, and pen-lift segmentation. Outputs M3 (pen down) and M5 (pen up) commands at stroke boundaries.

Key parameters:

Parameter	Effect
step	Point density - lower value gives smoother output (1 = maximum quality)
scale	Physical drawing size
dist threshold	Pen lift sensitivity - lower value reduces mid-stroke lifts

2. Serial Communication - Python

File: Circuits_and_Code/Plotter_Code.py

Transmits the generated G-code to the Arduino line by line over USB serial. Update the COM port and filename before running:

ser = serial.Serial('COM3', 115200)   # update port as needed
open("Yourgcodefilepath.gcode", "r")            # update filename to match output

3. Firmware - Arduino

File: Circuits_and_Code/Stepper_Servo_Controller.cpp

Custom G-code interpreter running on the Arduino. Parses incoming commands, drives X/Y steppers via the A4988 drivers, and controls the servo for pen actuation. Sends done over serial after each command is executed.

Supported commands:

Command	Action
G1 X__ Y__	Move to coordinate (drawing stroke)
G0 X__ Y__	Rapid travel (pen lifted)
M3	Lower pen (servo → 30°)
M5	Raise pen (servo → 90°)

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Repository Structure

CNC-PENPLOTTER/
├── 3d_Parts/                        ← SolidWorks assembly + STL files
├── Circuits_and_Code/               ← Arduino firmware, Python sender, circuit diagram, wiring reference
├── Demo_Media/                      ← Build photos and demo video
├── Image_to_GCode/                  ← MATLAB script, sample input image, sample G-code, simulation output
├── 2d-Printer List of Items.csv     ← Bill of materials
└── README.md

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How to Run

1. Upload  Stepper_Servo_Controller.cpp  to Arduino via Arduino IDE (USB only, no 12V)
2. Run     ImagetoGCodeConverter.m       in MATLAB - update image path and output path
3. Connect hardware - CNC shield on Arduino, steppers to X/Y headers, servo to Pin 11, 12V to shield
4. Run     python Circuits_and_Code/Plotter_Code.py  - update COM port if needed

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Acknowledgements

Developed as part of ME-205: Design Lab-I at the Indian Institute of Technology Ropar, under the supervision of Dr. Satwinder Jit Singh.

March 2026 - April 2026