I. Core Causes and Countermeasures
1. Welding spatter impacting the lens directly
Issue: Molten metal splashes or debris strike the lens surface at high speed, causing scratches or ablation spots.
Solutions:
Adjust welding angle: Maintain a 45°–60° angle between the welding torch and the workpiece (not perpendicular) to reduce direct spatter impact on the lens.
Install anti-spatter baffles: Place detachable metal baffles (e.g., copper or stainless steel) in front of the lens to block large particles; clean or replace the baffles regularly.
Apply anti-spatter coatings: Coat the lens surface with a nano-scale fluorinated protective agent to reduce spatter adhesion and facilitate cleaning.
2. Sudden high-energy laser shock to the lens
Issue: Abrupt energy changes during laser on/off or improper parameters (e.g., excessive peak power) break down the lens coating.
Solutions:Optimize parameter settings:
Enable "ramp-up/ramp-down" functions (e.g., set 200–500ms for gradual laser activation/deactivation) to avoid sudden energy surges;
Reduce peak power or pulse width; for thin plates, use a "high-frequency low-energy" mode (e.g., 1000Hz pulse frequency with 10%–20% lower peak power).
Calibrate optical coaxiality: Use a red light alignment system to check the coaxiality of the laser beam and lens center, ensuring deviation < ±0.1mm to prevent edge burning.
II. Environmental and Maintenance Optimizations
3. Dust/oil contamination and improper cleaning
Issue: Metal dust or oily vapors in the work environment adhere to the lens, forming heat-absorbing layers that cause local overheating and cracking; cleaning with non-specialized tools scratches the lens.
Solutions:
Strengthen environmental dust removal: Install a negative-pressure dust collector (airflow ≥300m³/h) or dust curtains around the machine to minimize dust exposure.
Standardize cleaning procedures:
Wear dust-free gloves when removing the lens to avoid fingerprints;
First blow off surface dust with compressed air (purity ≥99.9%), then wipe gently with acetone/ethanol-moistened lint-free cloths (e.g., Kimtech Prime) in concentric circles (never wipe back and forth);
Never use regular tissue, cotton swabs, or hard objects. Inspect the lens under a 10x magnifier after cleaning.
4. Cooling system failure leading to lens overheating
Issue: Inadequate coolant flow, high water temperature, or clogged pipes prevent the lens from dissipating heat, causing thermal stress cracking.
Solutions:Monitor cooling parameters in real time:
Ensure coolant flow ≥3L/min and water temperature at 20–25°C (±2°C); install digital flowmeters and temperature sensors;
Check water quality weekly. Replace deionized water (conductivity < 10μS/cm) and clean pipes with 5% citric acid solution if water is turbid.
Inspect cooling components: Check for leaks in the water-cooled jackets of focusing/collimating lenses; replace seals immediately to prevent water contact with the lens.
III. Gas Protection and Optical System Calibration
5. Abnormal auxiliary gas causing lens contamination
Issue: Inadequate gas pressure (e.g., nitrogen <0.6MPa) or turbulent airflow allows metal vapor to backflow onto the lens, forming oxidation layers or carbon deposits.
Solutions:Optimize gas parameters:
Use a "coaxial + side-blow" composite gas protection mode: coaxial gas (nitrogen/argon) at 0.8–1.0MPa, side-blow gas at 0.4–0.6MPa, with a 30° angle to the welding direction;
For carbon steel welding, mix 5%–10% oxygen into the side-blow gas (control total amount to prevent lens oxidation) to vaporize slag and reduce spatter.
Replace gas filters regularly: Change the desiccant (e.g., molecular sieve) and oil-water separator cartridges every 500 hours to block moisture/oil.
6. Optical path deviation or focusing anomalies
Issue: Misaligned reflectors or loose focusing lenses cause the laser beam to hit the protective lens instead of the workpiece, leading to burns.
Solutions:Three-dimensional optical calibration:
Use a red light indicator to calibrate reflector coaxiality, ensuring red light offset <0.05mm at each lens center;
Verify focus position with the "paper burning method": A normal focus should punch a hole ≤0.3mm in diameter. If irregular burning or lens damage occurs, adjust the focusing lens height (precision ±0.01mm).
IV. Preventive Maintenance and Operation Protocols
7. Establish a lens life management system
Quantify replacement cycles: Replace lenses every 400 working hours or 100,000 welding cycles, or immediately if:
Surface scratches ≥0.1mm or dense ablation spots exist;
Light transmittance decreases by >15% (compare with a new lens using a laser power meter).
8. Specialized training for operators
Key operational points:
Never activate the laser without the protective lens installed;
After replacing workpieces, run an empty program to confirm the nozzle-to-workpiece distance (5–8mm) and spatter direction before welding;
Before long-term shutdown, purge the lens chamber with protective gas (flow 10L/min) for 5 minutes to prevent dust accumulation.
V. Solutions for Special Scenarios
9. Welding highly reflective materials (e.g., copper, aluminum)
Targeted measures:
Replace with Yb-doped laser-specific lenses (anti-reflection threshold ≥15J/cm²) to withstand high reflectivity;
Use "pulse waveform modulation" to convert sharp pulses to flat-top waves, reducing reflective energy shock on the lens.