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Mechanical & Creative Automation 2024 Private Project

CNC Painting Robot

Converted my MPCNC into a multi-color painting robot with gravity-fed tool system and 48-color palette, creating wall art with precision impossible to achieve by hand.

Project Overview

After mastering CNC milling, I wanted to push the machine into a completely different domain: art. By converting my MPCNC into a painting robot, I created a system capable of producing multi-color artwork with precision and repeatability far beyond what I could achieve manually.

The project combined mechanical design (tool-changing system), software engineering (G-code generation), and creative problem-solving (how to translate digital art into machine instructions). The resulting artwork exceeded my manual drawing capabilities and decorated my walls before I moved for my master's program.

Technical Achievement: Manual tool-changing system with self-aligning, gravity-fed pen/brush holders working across 48 colors with both pencils and acrylic paint.

Technical Design

Tool-Changing Mechanism

The heart of the system was a simple but effective tool-changing design:

  • Self-aligning holders: Drop-in tool holders that positioned each pen/brush consistently
  • Manual switching: I would swap tools between color layers (automated switching proved too complex)
  • Gravity-fed dispensing: Tools held vertically, paint/ink flowed by gravity and surface tension
  • Calibrated Z-height: Each tool programmed with precise contact pressure for consistent line weight

Color System

I worked with a palette of 48 base colors:

  • Pencils: Standard colored pencils that produced very consistent results
  • Acrylic paint: Brushes with fluid paint, more challenging but achieved painterly effects
  • Color mapping: Digital artwork color-separated into available palette colors
  • Layering strategy: Planned drawing order to minimize smudging and maximize clarity

Material Challenges

Different media presented distinct engineering problems:

  • Pencils: Easy to control, predictable, excellent for detail work
  • Acrylic paint: Inconsistent flow during large rapid movements; paper degradation over time from repeated passes
  • Paper saturation: Too much paint caused warping and bleeding
  • Drying time: Had to sequence colors to avoid wet-on-wet smearing

Technologies Used

CNC Conversion
Tool Design
G-code Generation
Prusa Slicer Hacking
Multi-color Workflows
Creative Automation

The Software Challenge: Generating G-code

The Problem

Converting artwork into CNC machine instructions proved harder than the mechanical build:

  • CNC software limitations: Standard CAM programs were painfully slow for artistic paths
  • Multi-color complexity: No existing tool designed for pen-plotter multi-color workflows
  • Tool changes: Needed coordinated pause points for manual tool swapping

The Solution: Hacking Prusa Slicer

I discovered an unconventional solution: repurpose 3D printing software for 2D art:

  1. Artwork preparation: Color-separate artwork into individual SVG files per color
  2. Import as 3D objects: Load each SVG into Prusa Slicer as if it were a 3D model
  3. Single-layer slice: Configure for one-layer-high "print" (essentially a 2D path)
  4. Multi-object slicing: Assign different "colors" to each SVG layer
  5. Automatic tool changes: Slicer generates pause commands between colors for tool swapping
Why This Worked: Prusa Slicer's multi-material workflow already solved the orchestration problem— I just applied it to pens instead of plastic extruders.

Profile Modifications

I customized Prusa Slicer settings for drawing instead of 3D printing:

  • Disabled all Z-axis movements except initial positioning
  • Adjusted "extrusion" parameters to control line weight
  • Tuned travel speeds to prevent paint splatter
  • Added custom G-code for tool-change pause points

Advanced Technique: Shading Experiments

Multi-Layer Color Mixing

I experimented with creating additional colors through layering:

  • Concept: Stack multiple pencil colors to create blended shades
  • Implementation: Slice artwork at multiple "heights" with different colors per layer
  • Results: Successfully created depth and shading effects beyond the 48 base colors
  • Limitation: Abandoned further work after achieving proof of concept

Why It Matters

The layering technique demonstrated that the system wasn't limited to flat coloring— it could produce genuinely artistic effects with proper G-code programming. This opened possibilities for:

  • Gradient effects through controlled overlap
  • Texture through varied line density
  • Depth perception through color layering

Results & Artwork

Output Quality

The finished pieces consistently exceeded my manual drawing ability:

  • Precision: Sub-millimeter positioning accuracy impossible to achieve by hand
  • Repeatability: Could reproduce identical artwork on demand
  • Detail level: Maintained fine details across large compositions
  • Time investment: Hours of machine time, but zero manual skill required during execution

Personal Impact

Several pieces decorated my apartment walls before relocating for my master's program:

  • Created artwork that I genuinely valued as decoration
  • Demonstrated that technical skill can enable creative expression
  • Proved that unconventional tool use (hacking slicer software) solves real problems
Creative Validation: These were genuinely better than anything I could draw manually— the machine amplified my artistic intent without requiring traditional artistic skill.

Key Learnings

Creative Automation

  • Tool repurposing: Machines designed for one purpose can excel at completely different tasks
  • Software creativity: The hardest part wasn't mechanics, it was translating art into machine instructions
  • Unconventional solutions: 3D printing software worked better than purpose-built CAM tools

Technical Skills

  • G-code mastery: Deep understanding of how to orchestrate complex multi-step processes
  • Software adaptation: Learned to bend existing tools to solve new problems
  • Workflow design: Created efficient pipelines from digital art to physical output

Material Science

  • Media properties: Different drawing materials have vastly different machine requirements
  • Substrate interaction: Paper quality and saturation limits matter for multi-pass work
  • Process tuning: Each material required custom speed, pressure, and sequencing parameters

Challenges & Limitations

What Worked Well

  • Pencil artwork: Highly reliable, excellent results
  • Manual tool changing: Simpler than automated systems, perfectly adequate
  • Prusa Slicer workflow: Faster than traditional CAM software by orders of magnitude

What Struggled

  • Paint consistency: Acrylic flow varied with large rapid movements
  • Paper degradation: Too many passes damaged the paper surface
  • Drying coordination: Had to carefully sequence layers to avoid smearing

Why I Stopped

The project achieved its core goal— demonstrating that creative automation was possible and producing artwork I valued. I moved on to other projects rather than refining the system further, but the techniques remain documented for future use.

Impact & Applications

This project influenced my approach to several subsequent builds:

  • Tool versatility: Machines should be designed for adaptation and repurposing
  • Software creativity: Often the best solution is repurposing existing software for new domains
  • Creative engineering: Technical skills can enable artistic expression without traditional training
  • Workflow automation: The principles apply to any multi-step creative or manufacturing process

Related Projects

This build connects to several other mechanical and creative works: