Optimizing a 1000W fiber laser for cutting stainless steel sheets requires precise tuning of parameters like laser power, cutting speed, focus position, auxiliary gas, and nozzle configuration. Below is a step-by-step guide based on industry best practices and technical insights from the knowledge base:
1. Key Parameters to Optimize
a. Laser Power
Recommended Setting: Use 80–100% of the maximum power (800–1000W) for stainless steel. Higher power ensures sufficient energy to overcome the material’s high reflectivity and thermal conductivity.
Caution: Avoid excessive power (e.g., >100%) to prevent burning, warping, or damaging the material.
b. Cutting Speed
General Rule:
Thin Sheets (≤3mm): Use 20–30 m/min for clean, high-speed cuts.
Medium Sheets (3–6mm): Adjust to 15–25 m/min to balance speed and precision.
Thicker Sheets (6–10mm): Reduce to 10–15 m/min to ensure full penetration and minimize dross.
Testing: Start with lower speeds for thicker materials and gradually increase while monitoring cut quality.
c. Focus Position (Negative vs. Positive Focus)
Negative Focus (focus point below the material surface):
Enhances melt pool stability and reduces heat-affected zones (HAZ).
Ideal for stainless steel to prevent oxidation and achieve smoother edges.
Recommended Offset: -0.5 to -1.5 mm (adjust based on material thickness).
Positive Focus (focus point above the material):
Less common for stainless steel but may be used for thin sheets (<1mm) to improve surface finish.
d. Auxiliary Gas
Gas Type:
Nitrogen (N₂): Prevents oxidation, leaving a clean, stainless-steel-colored edge.
Oxygen (O₂): Increases cutting speed but results in oxidized (blackened) edges.
Air: Cost-effective but produces lower-quality cuts (yellowish edges).
Gas Purity:
Nitrogen: ≥99.995% for high-quality, oxidation-free cuts.
Oxygen: ≥99.999% for thick plates.
Gas Pressure:
Thin Sheets (≤3mm): 1–2 bar.
Medium Sheets (3–6mm): 2–3 bar.
Thicker Sheets (6–10mm): 3–4 bar (ensure nozzle and system can handle higher pressure).
e. Nozzle Diameter
Selection:
3–6mm Sheets: Use a 1.0–1.2mm diameter nozzle for precise gas flow and molten material removal.
6–10mm Sheets: Upgrade to a 1.5–2.0mm nozzle to increase gas volume and reduce dross.
Check for Damage: Ensure the nozzle is undamaged and has a smooth, circular opening. Replace if worn or clogged.
f. Cutting Height
Ideal Range: 0.8–1.2mm above the material surface.
Adjustment: Use the blue spark method (as described in [7]) to locate the focal point.
Remove the nozzle, blow air, and move the laser head vertically until blue sparks peak—this indicates the optimal focus.
2. Step-by-Step Optimization Process
Preparation
Clean the material surface to remove oils, rust, or coatings.
Ensure the laser head is aligned and the nozzle is undamaged.
Initial Setup
Set the laser power to 80% and cutting speed to 20 m/min for a 3mm stainless steel sheet.
Use a 1.0mm nozzle with nitrogen at 2 bar.
Focus Adjustment
Perform a blue spark test to locate the focal point.
Adjust the focus to -1 mm (negative focus) for optimal melt pool control.
Test Cuts
Cut a test sample and inspect for:
Smooth edges with minimal dross.
No oxidation (if using nitrogen).
Uniform cut width (typically 0.5mm for 1000W lasers).
Parameter Tuning
If Dross Forms:
Increase gas pressure by 0.5–1 bar.
Slightly lower the focus (e.g., from -1 mm to -1.5 mm).
If Edges Are Rough:
Decrease cutting speed by 5–10%.
Check nozzle alignment and gas purity.
If Burn Marks Appear:
Reduce laser power to 70–80%.
Increase cutting speed to avoid heat accumulation.
Advanced Adjustments
For thicker sheets (6–10mm):
Use a 1.5mm nozzle and 3 bar nitrogen pressure.
Reduce speed to 10–15 m/min and lower the focus to -1.5 mm.
For thin sheets (<3mm):
Increase speed to 30 m/min and use a 1.0mm nozzle.
3. Common Issues & Solutions
Problem
Cause
Solution
Dross Formation
Insufficient gas pressure or focus
Increase gas pressure by 0.5–1 bar; adjust focus to -1.5 mm.
Oxidation (Black Edges)
Using oxygen instead of nitrogen
Switch to nitrogen gas (≥99.995%).
Rough Edges
Low cutting speed or misalignment
Increase speed by 5–10%; realign nozzle and check focus.
Burn Marks
Excessive power or slow speed
Reduce power to 70–80%; increase speed to disperse heat.
4. Safety and Maintenance Tips
Cooling System: Ensure the water chiller maintains a stable temperature (20–30°C) to prevent laser tube overheating.
Lens and Nozzle Cleaning: Clean the focusing lens and nozzle regularly to avoid contamination affecting beam quality.
Gas Cylinder Safety: Secure gas cylinders and monitor pressure gauges to prevent leaks.
Workpiece Fixation: Clamp the material securely to avoid vibrations that may disrupt the cut path.
5. Example Settings for 1000W Fiber Laser
Material Thickness
Laser Power
Speed
Focus
Gas Type
Nozzle Diameter
Gas Pressure
2–3mm Stainless Steel
800–900W
25–30 m/min
-1 mm
Nitrogen
1.0 mm
2 bar
4–6mm Stainless Steel
900–1000W
15–20 m/min
-1.2 mm
Nitrogen
1.2 mm
3 bar
8–10mm Stainless Steel
950–1000W
10–12 m/min
-1.5 mm
Nitrogen
1.5 mm
4 bar
By following these guidelines and conducting iterative test cuts, you can achieve high-quality, efficient cuts on stainless steel sheets using a 1000W fiber laser. Always prioritize safety and regular maintenance to prolong equipment lifespan and ensure consistent performance.
