CNC Simulation Software: Best Options for Testing Your G-Code Before You Cut
Running untested G-code on a real machine is like playing roulette — one mistake could break a tool, damage the fixture, or even crash the spindle.
CNC simulation software allows you to verify and visualize your G-code before it hits the machine.
In this guide, we’ll cover:
- Why simulation matters
- Best software (free and paid)
- Features to look for
- Pro tips from real shops
🎯 Why Simulate G-Code?
✅ Catch programming errors (missing tool call, invalid G-code)
✅ Visualize toolpaths, feeds, and approach moves
✅ Prevent machine crashes and overtravel
✅ Improve confidence in post-processed CAM output
✅ Reduce scrap and downtime
🧰 1. NC Viewer (Free, Web-Based)
Website: ncviewer.com
- Simple, lightweight G-code visualizer
- Real-time toolpath preview
- Shows XYZ coordinates, tool movement
- Supports basic G-code (G00–G03, G81, etc.)
✅ Best for:
- Students, hobbyists, quick checks
- Milling and turning basics
⚠️ Limitations:
- No solid simulation or machine constraints
- No multi-axis support
💻 2. CAMotics (Open Source, Desktop)
Website: camotics.org
- 3D material removal simulation
- Imports standard G-code
- Customizable cutting tools
- Mill-only (no turning)
✅ Best for:
- Small shops, makers, education
- Seeing actual cutting geometry
⚠️ Limitations:
- No support for canned cycles or macros
- Limited machine definitions
🔧 3. Predator Virtual CNC (Paid)
Website: predator-software.com
- Real-time machine simulation
- Supports Fanuc, Haas, Siemens, Mazak
- Collision detection with solid models
- Macro B, subprograms, canned cycles supported
✅ Best for:
- Professional job shops, production environments
- Simulating entire setup + machine
💲 Pricing:
- Starts around $2,000–$4,000 per seat
🔬 4. Vericut by CGTech (Industry Standard)
Website: cgtech.com
- Gold-standard for high-end CNC simulation
- Full material removal, stock setup, fixturing
- Optimizes feeds/speeds and toolpaths
- Supports 5-axis, probing, macro logic
✅ Best for:
- Aerospace, medical, high-cost parts
- Companies with multi-million dollar spindles
💲 Pricing:
- Expensive ($10,000+ typical setup)
💡 Pro shops use Vericut before every new program hits the floor.
⚙️ 5. Fusion 360 Simulation (Built-in)
Platform: Autodesk Fusion 360
- CAM + simulation integrated
- Visual toolpaths and material removal
- Stock setup, collision detection
- Great for 3-axis and 5-axis milling
✅ Best for:
- Fusion CAM users
- Job shops looking for all-in-one workflow
🧠 Features to Look For
| Feature | Why It Matters |
|---|---|
| Solid Model Simulation | See actual part being cut |
| Machine Constraints | Prevent axis overtravel or collision |
| Controller Emulation | Run Fanuc/Haas/Siemens G-code accurately |
| Tool & Holder Models | Detect spindle or fixture crashes |
| G65/M98 Support | Required for advanced G-code |
🧰 Comparison Table
| Software | Platform | Price | Best Use Case |
|---|---|---|---|
| NC Viewer | Web | Free | Basic syntax check |
| CAMotics | Desktop | Free | Hobbyist, visualizing cuts |
| Predator CNC | Desktop | $$$ | Pro shop, real machine emulation |
| Vericut | Desktop | $$$$ | Enterprise-level simulation |
| Fusion 360 Sim | Fusion | $$$ | CAM-integrated verification |
🧠 Real-World Pro Tips
- Always simulate with actual tool lengths and holders
- Import real stock and fixture models for accurate results
- Simulate G28, G91, and subprograms — they often cause crashes
- Export collision reports for quality audits
- Integrate simulation with your CAM post-processor workflow
🛡️ Simulation Saved This Shop:
“We caught a G00 move going to Z-200 by mistake — would have hit the table with a 150mm shell mill. Saved a $5,000 fixture and a full day of rework.”
— CNC Programmer, Aerospace Tier 1 Supplier
🎯 Final Thoughts
Simulation isn’t optional — it’s an insurance policy.
Before every tool touches metal, make sure your code runs clean, safe, and efficient in virtual space.
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