Burrs—those unwanted raised edges or excess material left after cutting—are a common issue in laser processing, especially when drilling or cutting small holes (typically <1.5x material thickness). While minor burring might be acceptable in some applications, excessive burrs compromise fit, function, safety, and aesthetics, requiring costly secondary operations.
In this guide, we’ll analyze why burrs form during small-hole laser cutting and provide actionable strategies to optimize parameters and eliminate them.
Why Do Burrs Form in Small Holes?
Burring happens when molten material fails to eject cleanly from the kerf and instead re-solidifies on the exit side (usually the bottom). Several factors contribute specifically to burr formation in small features:
1. High Aspect Ratio
Small holes in thick materials create a high aspect ratio (depth/diameter), restricting gas flow and making it harder to expel molten metal.
2. Turbulent Assist Gas Flow
Narrow kerfs disrupt laminar gas flow, leading to turbulence that reduces momentum and ejection efficiency.
3. Improper Focus Position
Incorrect focal point placement affects energy density and penetration. Too high or too low = weak piercing capability and poor melt removal.
4. Excessive Pulse Energy or Slow Piercing
Aggressive piercing settings can cause splashback and remelted material accumulation around the hole entrance.
5. Dull or Damaged Nozzles
Even slight nozzle wear alters gas dynamics, reducing coherence and shear force needed for clean ejection.
6. Material Variability
Coatings, rust, or uneven thickness can interfere with consistent cutting behavior.
Parameter Optimization Strategies to Reduce Burrs
�� 1. Adjust Focus Position
For small holes, set the focus slightly below the top surface (e.g., 1/3 into the material). This ensures maximum intensity at the entry point and maintains strong gas velocity through the kerf.
Try multiple focus tests (e.g., -0.5 mm to +1.0 mm relative to surface) and inspect burr height under magnification.
�� 2. Use Pulsed Mode Instead of Continuous Wave (CW)
Pulsed laser operation allows controlled energy delivery:
· Short pulses reduce heat accumulation
· Peak power remains high for penetration
· Off-time lets molten pool stabilize before next pulse
Recommended pulse durations: 0.1–0.5 ms for thin sheets; longer for thick plates.
�� 3. Optimize Pierce Settings
Avoid full-power piercing. Use a multi-stage pierce:
· Stage 1: Low-power pre-pierce to initiate hole
· Stage 2: Ramp-up to cutting power
· Stage 3: Delay before motion starts (allow debris clearance)
Reduce pierce time and height to limit exposure.
�� 4. Increase Nozzle Standoff Height (Slightly)
Sometimes increasing standoff by 0.2–0.5 mm improves gas coverage around small holes—but don’t go too high, or beam divergence worsens.
�� 5. Select Smaller Nozzle Diameter
A narrower nozzle (e.g., 1.0 mm vs. 1.5 mm) increases gas velocity and concentration, improving melt ejection in tight spaces.
But ensure clearance isn’t compromised during piercing.
�� 6. Raise Assist Gas Pressure
Higher pressure enhances melt expulsion. For nitrogen cutting:
· 1 mm steel: ~12 bar
· 3 mm steel: ~18–20 bar Verify regulator and hose integrity to avoid pressure drops.
�� 7. Reduce Cutting Speed Near Corners or Holes
Apply corner/slot slowdown functions in CNC controls. Slowing down just before entering a hole maintains stable keyhole conditions.
�� 8. Use Taper Compensation (if available)
Some software adjusts path geometry dynamically to counteract natural taper in holes—especially useful for precision parts.
Machine & Process Enhancements
Beyond parameters:
· Upgrade to auto-nozzle changers for consistent alignment
· Install capacitive height sensors to maintain Z-axis accuracy
· Use anti-spatter coatings on nozzles and protective shields
· Monitor beam mode quality regularly via diagnostic tools
Validation: Measuring Burr Reduction
Quantify improvement using:
· Optical profilometry
· Tactile gauges
· Microscopic inspection (100x zoom) Define acceptable burr height (e.g., <0.1 mm) and document before/after comparisons.
Final Thoughts
Eliminating burrs in small holes requires both precision tuning and disciplined maintenance. There's no universal setting—each material, thickness, and hole size demands its own optimal recipe.
Invest time in parameter development, leverage pulsed modes and smart piercing, and never underestimate the impact of clean, well-aligned consumables.
With the right approach, you can achieve burr-free micro-holes ready for assembly—without deburring.
@taidinggroup