Q1: What laser power is required for copper welding?

AnswerThe required power is lower than you might think — provided you have optimal beam quality.

Copper reflects approximately 95% of 1070nm laser light at room temperature. A power density of around 100 MW/cm² is needed to break through this reflectivity and form a stable keyhole.

Practical references:

• 14μm single-mode fiber @ 1,500W → ~100 MW/cm² ✅ Meets the threshold perfectly

• 100μm multi-mode fiber @ 6,000W → ~50 MW/cm² ❌ Below the threshold

For thin copper sheets (0.2–2mm), a 1.5–3kW single-mode laser outperforms 6–10kW multi-mode systems.

Power density, not raw power, is the core factor.

Q2: Single-mode or multi-mode laser — How to choose?

AnswerThe choice boils down to one priority: precision or penetration depth.

Single-mode (M² < 1.3)

• Applicable for copper/aluminum sheets thinner than 3mm

• Ideal for applications requiring precise weld geometry: EV batteries, flat wire motors, medical devices

• Recommended power range: 1–4kW

Multi-mode

• Suitable for plates thicker than 5mm

• Used for high-throughput tasks demanding deep penetration, where weld appearance is not a top priority

• Recommended power: 6kW and above

Define your application requirements first, then select the corresponding beam quality.

Q3: Why is there excessive spatter during copper welding?

AnswerThree major causes, ranked by likelihood:

1. Power density below the keyhole thresholdSolution: Increase power density by using a smaller spot size, raising laser power, or combining both methods.

2. Unstable keyhole geometryA single beam generates asymmetric vapor jets, which destabilize the keyhole opening.Solution: Adopt Focused Ring Mode (FRM) beam shaping. FRM reduces spatter by 60–80% compared with standard single-mode beams for copper busbar welding.

3. Surface contaminationEven slight oxidation will alter local laser absorptivity.

Traditional Laser Welding vs. GW FRM Welding

Q4: Causes and solutions for porosity in aluminum laser welding

AnswerThere are three fundamental causes:

1. Hydrogen porosityDissolved hydrogen gets trapped as the weld pool solidifies.Solution: Thorough pre-treatment, use dry welding wires, and adopt high-purity argon (99.999%).

2. Keyhole porosityThe keyhole collapses before internal gas escapes completely.Solution: Apply power modulation or slightly defocus the laser beam.

3. Failure to reach the stable keyhole thresholdThe stable keyhole threshold for aluminum is over 3.5 MW/cm².

Q5: What is BPP, and why is it more important than M²?

Answer

• The M² factor indicates how close a laser beam is to an ideal Gaussian beam. It is only valid for comparing lasers with the same wavelength and aperture.

• BPP (Beam Parameter Product) determines the actual minimum focusable spot size.

Formula:BPP = Beam waist radius (mm) × Half-angle divergence (mrad)

Examples:

• 14μm fiber / 0.065 NA → BPP ≈ 0.45 mm·mrad

• 50μm fiber / 0.12 NA → BPP ≈ 3.0 mm·mrad

A lower BPP means a tighter focused spot and higher power density. For copper welding with a 3kW laser, the BPP should be ≤ 0.5 mm·mrad.

Q6: Can fiber lasers replace TIG welding?

AnswerFor most thin-sheet applications, yes.

• Speed: Fiber laser welding is 5 to 20 times faster than TIG welding for equivalent workpieces.

• Heat input: Lasers create a narrower, localized heat-affected zone (HAZ), resulting in less workpiece deformation.

• Automation: TIG welding relies on skilled operators, while fiber laser welding is fully automatable.

For components with wall thickness below 4mm, the cost of switching to laser welding is typically recouped within 12 to 18 months.

Q7: Which shielding gas should be used for laser welding?

Answer

• Argon: Universal choice for copper, aluminum, stainless steel and titanium, cost-effective.

• Helium: Ideal for power above 4kW and deep penetration welding; provides better plasma suppression but comes at a higher cost.

• Argon-Helium mixture: Recommended for stainless steel and titanium welding at 6kW and above.

• Nitrogen: Used for non-critical carbon steel welding with the lowest cost. Do not use on stainless steel or reactive metals.

Q8: How to select the proper delivery fiber core diameter?

AnswerThe delivery fiber determines the minimum focusable spot size and maximum achievable power density.

• 14–20μm: For copper welding and high-precision applications, matching 1–4kW lasers.

• 50μm: For general welding and thin-sheet cutting, matching 3–10kW lasers.

• 100μm: For thick plate welding and structural component processing, matching 6–20kW lasers.

Note: Smaller-core fibers require a smaller bending radius, especially for laser heads mounted on robots or collaborative robots.

Q9: Conduction welding vs. Keyhole welding — What are the differences?

Answer

• Conduction Welding (< 1 MW/cm²)Energy is absorbed by the material surface and transferred via thermal conduction. It produces a wide, shallow weld pool with minimal spatter.

• Keyhole Welding (> 1–5 MW/cm², varies by material)The laser vaporizes the material to form a gas-filled cavity (keyhole), which greatly improves energy coupling. It delivers narrow weld seams with deep penetration.

For copper, the keyhole threshold is approximately 20 MW/cm². This explains why high-brightness single-mode lasers are essential for copper keyhole welding.

Q10: How to tell if a fiber laser requires maintenance?

Answer

Urgent maintenance required (immediate action)

• Output power drops by more than 5%

• Deteriorated beam quality

• Unexpected thermal shutdown

• Photoelectric detector alarms

Quarterly routine inspection

• Clean all fiber connectors in accordance with IEC 61300-3-35 standards

• Inspect delivery fibers for damage

• Verify the performance of the cooling system

Primary failure cause

Dirty or damaged fiber connectors. Always inspect connectors before reconnection.