Achieving a mirror-like finish in CNC machining isn't just about the tools; it’s about how the machine interprets movement. Traditional CAM outputs can sometimes lead to faceted surfaces or micro-stutters. In this guide, we dive into G-Code tuning techniques to unlock ultra-smooth machined surfaces.
1. Understanding Constant Velocity Mode (G64)
By default, some controllers might pause slightly between motion blocks to ensure exact positioning. This causes "dwell marks." Using G64 (Constant Velocity) allows the tool to maintain momentum, smoothing out the transitions between line segments.
G64 P0.001 ; Set constant velocity with a 0.001mm tolerance
2. Fine-Tuning Feed Rate Optimization
Surface roughness ($Ra$) is heavily influenced by the feed rate and tool geometry. For finishing passes, use a smaller Stepover and a consistent Feed Rate (F). To avoid vibration, ensure your spindle speed ($S$) is synchronized with your chip load.
3. High-Speed Look-Ahead (G05.1 Q1)
Modern controllers like Fanuc use High-Speed Look-Ahead. This command pre-processes hundreds of lines of G-code to smooth out complex 3D contours, preventing the "stuttering" effect on curved surfaces.
G05.1 Q1 ; Enable AI Nano High-Speed Control
G43 H1 Z10.0 S12000 M3 ; Start finishing pass
4. Arc Interpolation over Linear Segments
Instead of thousands of tiny G1 (linear) moves, use G2/G3 (circular interpolation). This reduces the data load on the controller and results in a much more fluid toolpath trajectory.
Key Takeaways for Smooth Finishes:
- Always use lead-in and lead-out moves to avoid plunge marks.
- Check your G-code tolerance settings in CAM; 0.005mm is often the "sweet spot" for finishing.
- Ensure the machine's Look-Ahead buffer is active.
