ARAVIND SUNDARARAJAN

Project Overview

SunnyCNC is a custom-built CNC machine designed to run on CircuitPython or PyCNC with ROS (Robot Operating System) integration. The project represents an ambitious attempt to create a fully open-source CNC solution with modern control systems, combining the flexibility of Python-based control with the reliability of established CNC firmware.

The machine features a modular design with 3D-printed components, NEMA stepper motors, and a Proxxon Micromot 50 spindle. The control system is built around a Raspberry Pi 3B+ for high-level control and an Arduino Mega 2560 with RAMPS shield for motor control, providing a hybrid approach that leverages the strengths of both platforms.

Note: This project is currently in active development and redesign. The initial gantry design proved to be too massive, causing significant kickback and oscillations with the Dremel tool. A revised design with improved structural rigidity and reduced mass is in progress.

System Architecture

SunnyCNC machine showing the overall structure and component layout

Control System Design

The SunnyCNC employs a dual-processor architecture for optimal performance:

• Raspberry Pi 3B+ - High-level control, G-code processing, and potential OctoPrint integration
• Arduino Mega 2560 - Real-time motor control and motion planning
• RAMPS Shield - Motor driver interface and power distribution
• CircuitPython/PyCNC - Flexible control software with ROS compatibility

Mechanical Design

The machine uses a Cartesian coordinate system with the following components:

• X-Axis - Dual NEMA-17 stepper motors for gantry movement
• Y-Axis - Single NEMA-17 stepper motor for bed movement
• Z-Axis - Single NEMA-17 stepper motor for vertical positioning
• Spindle - Proxxon Micromot 50 with custom mounting system
• Frame - 3D-printed components with aluminum extrusion support

Component Selection

Power System

12V Rail:
- Proxxon Micromot 50 spindle
- NEMA-17 stepper motors
- RAMPS shield electronics

5V Rail:
- Raspberry Pi 3B+
- Arduino Mega 2560
- Control electronics

Note: Custom power supply design to avoid 
proprietary Proxxon power supply costs

Software Implementation

Control Software Stack

The SunnyCNC uses a sophisticated software architecture:

• CircuitPython/PyCNC - High-level control and G-code interpretation
• ROS Integration - Robot Operating System for advanced control algorithms
• Marlin Firmware - Modified for CNC operations on Arduino
• OctoPrint Compatibility - Web interface for machine control (planned)

Firmware Modifications

The project includes custom modifications to Marlin firmware:

• G-code Compatibility - Full support for standard CNC G-code commands
• Spindle Control - PWM control for variable speed operation
• Safety Features - Emergency stop and limit switch integration
• Communication Protocol - Serial communication with Raspberry Pi

Python Control Scripts

Custom Python scripts provide flexible control:

• G-code Parser - Converts G-code to motor commands
• Motion Planning - Optimizes tool paths for smooth operation
• ROS Nodes - Integration with Robot Operating System
• Web Interface - Browser-based control panel

Design Issues & Lessons Learned

Current Design Problems:

• Gantry Mass - The current gantry design is too massive, causing significant kickback during operation
• Oscillations - The heavy gantry creates unwanted vibrations that affect cutting quality
• Structural Rigidity - Insufficient stiffness in the frame leads to deflection under load
• Tool Stability - Dremel tool mounting system needs improvement for better stability

Technical Analysis

The primary issues stem from fundamental mechanical design principles:

• Mass Distribution - Excessive mass in moving components increases inertia and reduces responsiveness
• Resonance - The current design has natural frequencies that coincide with operating speeds
• Damping - Insufficient damping mechanisms to absorb vibrations
• Material Selection - 3D-printed parts may not provide sufficient rigidity for precision applications

Impact on Performance

These design issues significantly affect machine performance:

• Cutting Quality - Vibrations create poor surface finish and dimensional inaccuracy
• Tool Life - Excessive vibrations reduce tool life and cause premature wear
• Speed Limitations - Machine must operate at reduced speeds to minimize oscillations
• Precision - Positional accuracy is compromised by structural deflection

Redesign Plans

The SunnyCNC project is currently undergoing a comprehensive redesign to address the identified issues:

Structural Improvements

• Lightweight Gantry - Redesign with aluminum extrusions and optimized geometry
• Enhanced Rigidity - Improved frame design with better load distribution
• Damping Systems - Integration of vibration damping materials and mechanisms
• Material Optimization - Strategic use of different materials for strength vs. weight

Mechanical Enhancements

• Linear Rail Systems - Upgrade from basic bearings to precision linear rails
• Ball Screw Drives - Replace lead screws with ball screws for better precision
• Improved Spindle Mount - Redesigned mounting system for better tool stability
• Counterbalance Systems - Implement counterweights or gas springs for Z-axis

Control System Upgrades

• Advanced Motion Control - Implement adaptive feed rate control
• Vibration Monitoring - Add sensors to detect and compensate for vibrations
• Real-time Optimization - Dynamic adjustment of cutting parameters
• Improved Safety - Enhanced emergency stop and monitoring systems

Project Files & Documentation

3D Models & CAD Files

The project includes comprehensive CAD documentation:

• OpenSCAD Files - Parametric 3D models for all custom components
• STL Files - Ready-to-print 3D models
• Gantry Components - X-axis gantry with support structures
• Motor Mounts - NEMA-17 and NEMA-8 motor mounting systems
• Bearing Systems - Linear bearing mounts and guides
• Spindle Holder - Custom Proxxon Micromot mounting system

Firmware & Software

• Marlin 2.0.x - Modified Marlin firmware for CNC operations
• CircuitPython Scripts - Control and communication software
• Configuration Files - Machine-specific settings and parameters
• Documentation - Setup guides and troubleshooting information

Bill of Materials

Electronics:
- Raspberry Pi 3B+
- Arduino Mega 2560
- RAMPS 1.4 Shield
- 4x NEMA-17 Stepper Motors
- A4988 Stepper Drivers

Mechanical:
- Proxxon Micromot 50
- Linear Bearings
- Lead Screws
- Aluminum Extrusions
- 3D-Printed Components

Power:
- 12V Power Supply
- Custom Power Distribution

Project Significance

The SunnyCNC project demonstrates several important engineering and development skills:

• Systems Integration - Combining multiple control platforms and software systems
• Mechanical Design - Complex mechanical system design with real-world constraints
• Firmware Development - Custom modifications to open-source firmware
• Problem Analysis - Systematic identification and analysis of design issues
• Iterative Development - Continuous improvement based on testing and feedback

This project showcases the ability to tackle complex hardware challenges and demonstrates honest self-assessment when designs don't meet expectations. The willingness to acknowledge issues and plan improvements shows professional engineering maturity.

Future Development

The SunnyCNC project has a clear roadmap for improvement:

• Redesigned Gantry - Lighter, stiffer design with better vibration characteristics
• Advanced Control - Implementation of adaptive control algorithms
• Material Testing - Evaluation of different materials and construction methods
• Performance Validation - Comprehensive testing of the redesigned system
• Documentation - Complete build guide and lessons learned

The project represents an ongoing learning experience in CNC machine design and serves as a valuable case study in the importance of proper mechanical design principles.