📋 How to Use This Guide
- Bookmark & Search: Jump to the letter or term you need.
- Clickable TOC: (Implement with anchors in your CMS.)
- Code Snippets: Copy/paste ready for your machine controller.
- Advanced Tips: In every section, find pro-level notes.
🔠 A
Axis (Axes)
Definition: The directions in which a CNC machine can move a tool or workpiece—commonly X, Y, and Z, with rotational A, B, C axes on multi-axis machines.
Pro Tip: On a 5-axis mill, use head-tilt (A) for complex curves; table-rotate (B/C) for undercuts.
🔡 B
Backlash
Definition: The “dead zone” when reversing motion due to mechanical play in screws/gears.
Impact: Causes dimensional inaccuracy in bidirectional cuts.
Mitigation: Use ball screws with minimal backlash, and compensate in your controller (e.g. Fanuc’s “backlash compensation” parameter).
🔠 C
CAD (Computer-Aided Design)
Definition: Software (Fusion 360, SolidWorks) for creating 2D/3D part models.
Workflow Tip: Always export as native or STEP files to CAM for full feature compatibility.
CAM (Computer-Aided Manufacturing)
Definition: Software (Mastercam, HSMWorks) generates toolpaths from CAD models.
gcode; Example CAM-generated header
%
(Part: Bracket v1.2)
G21 G17 G90 ; mm, XY plane, abs.
Advanced: Use adaptive clearing strategies to maintain constant chip load on hard alloys.
Chip Load
Definition: The thickness of material removed per tooth per revolution.
Formula: Chip Load = Feed Rate / (RPM × # Flutes)
🔠 D
Drill Canned Cycle (G81)
gcodeG81 X20 Y10 Z-5 R2 F100 ; Drill to –5mm, retract to +2mm
Notes:
- Use G98 (retract to initial plane) vs G99 (retract to R-plane) depending on fixture.
- Always cancel with G80 at cycle end.
🔠 E
End Mill
Definition: A multi-flute cutter for milling operations.
Types: Flat, ball-nose, corner-radius, chamfer, roughing.
Usage: For 3D finishing, choose ball-nose with small stepover (10–15 % D) at high RPM.
🔠 F
Feed Rate (F)
Definition: Tool traverse speed (mm/min or in/min).
Example:
gcodeG01 X50 Y0 F300 ; Cut at 300 mm/min
Optimization: Start 10 % below recommended and tune for chatter reduction.
🔠 G
G00 – Rapid Positioning
gcodeG00 X0 Y0 Z5 ; Rapid to X0 Y0 at 5mm above part
Tip: Limit rapid Z height to avoid long non-cut moves.
G01 – Linear Interpolation
gcodeG01 Z-5 F100 ; Controlled plunge at 100 mm/min
G02/G03 – Circular Interpolation
gcodeG02 X10 Y0 I5 J0 F200 ; CW half-circle radius 5mm
Note: Ensure correct plane selection (G17/G18/G19) prior to arc moves.
🔠 H
Home/Limit Switches
Definition: Sensors that detect axis zero positions and prevent overtravel.
Setup: Always run Homing sequence at startup to establish WCS.
🔠 I
IJK Offsets
Definition: Relative center offsets for G02/G03 arcs.
Example: I-5 J0 for a center 5 mm left of start point.
🔠 J
(See IJK Offsets above.)
🔠 K
Kerf
Definition: Width of cut removed by the tool or beam (laser, plasma).
Adjustment: For precision holes, adjust toolpath by half the kerf width on each side.
🔠 L
Linear Guideways
Definition: Rails with recirculating bearings for smooth, precise linear motion.
Maintenance: Keep lubricated; inspect for debris monthly.
🔠 M
M03/M04 – Spindle On (CW/CCW)
gcodeM03 S12000 ; Spindle ON CW at 12,000 RPM
M05 – Spindle Off
gcodeM05 ; Stop spindle
M06 – Tool Change
gcodeT02 M06 ; Change to tool #2
🔠 N
N-Line Numbers
Definition: Sequential labels (N10, N20…) for easier code editing and restarts.
Practice: Use increments of 10 to allow insertion.
🔠 O
Offset (G43/G44/G49)
Definition: Tool length and diameter compensation for accurate probing.
gcodeG43 H02 ; Apply tool length offset #2
🔠 P
Peck Drilling (G83)
gcodeG83 X10 Y10 Z-10 R1 Q2 F100 ; Peck drill to -10mm, retract Q=2mm each peck
Use: Deep holes where chip clearance is critical.
🔠 Q
(See G83 above.)
🔠 R
R-Plane
Definition: Retract plane height parameter in canned cycles.
Tip: Set just above part surface to optimize cycle time.
🔠 S
Spindle Speed (S)
Definition: Tool rotation rate (RPM).
Example: S5000 for 5,000 RPM.
Formula: RPM = (SFM × 1000) / (π × D) for metric.
🔠 T
Toolpath
Definition: The programmed trajectory that the cutter follows.
Visualization: Always simulate in CAM before running.
🔠 U
Undercut
Definition: Feature requiring specialized tooling to machine recesses.
Solution: Use custom undercut tools or angled approach.
🔠 V
V-Groove
Definition: A profile with a V-shaped cross-section, commonly for decorative or functional channels.
🔠 W
Work Coordinate System (G54–G59)
Definition: Defines part zero location relative to machine zero.
Example: G54 for primary WCS, G55 for secondary.
🔠 X, Y, Z
Definition: Cartesian axes for position commands (e.g., X25 Y10 Z-5).
🚀 Advanced Appendix: Multiaxis & Automation Terms
- 5-Axis Indexing (G68/G69): Rotate coordinate system for angled features.
- Probing Cycle (G31): Feed until probe signal, used for work offset setting.
- Macro Programming (#1, #100…): Variables and loops for conditional logic.
- Engraving/Pocket Blending: Use fine stepover and multiple passes for smooth pockets.
📘 Conclusion & Next Steps
This CNC Encyclopedia is your definitive, always-available reference. Whether you’re debugging code, setting up a new job, or training team members, you’ll find everything you need here.
- Copy & paste code examples directly into your controller.
- Bookmark for daily use.
- Contribute new terms or examples at cnccode.com.
Keep this guide at your side in the shop, and visit cnccode.com for regular updates, deep-dive tutorials, and a thriving CNC community.
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