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Focus Guide

Master laser welding focus.

The focal point position is the single biggest lever for weld quality. Learn how Positive, Negative, and Zero Focus behave on different materials, see the beam path diagram, and ask our assistant for instant guidance.

Understanding Focus

Positive, Negative, Zero.

The focal point can sit above, on, or below the material surface. Each setting trades energy density for spot size and penetration depth.

MATERIALFocal point on surface(Zero Focus — max surface density)

(Zero Focus — max surface density)

OFFSET RANGE

0mm (on the surface)

Focal point exactly on the material surface — max surface density.

ENERGY DENSITY

Smallest spot, highest surface density, fastest welding.

Best for

  • Thin sheets and high-speed welding
  • Copper (breaks the oxide layer)
  • Galvanized steel (breaks zinc coating)
  • Stainless steel with tight cosmetic requirements

Avoid for

  • Thick plates (too tight for wide pools)
  • Wide-gap joints (no width to bridge)

Pro Tip

For copper, never defocus — any positive offset loses the density needed to break the oxide layer.

Material Guide

Recommended focus by material.

Different metals absorb and conduct laser energy very differently. Here is the recommended starting focus for the most common welding materials.

Carbon Steel

Easy

Most common material, good laser absorption.

RECOMMENDED FOCUS

Zero Focus (0mm (on the surface))

Challenges

  • Standard welding conditions apply
  • Watch excessive heat input on thin gauges

Pro Tips

  • Start with Zero Focus and adjust based on penetration
  • Use Nitrogen shielding for cleaner welds
  • Switch to Negative Focus for plates over 3 mm

Stainless Steel

Easy

Low thermal conductivity, high aesthetic requirement.

RECOMMENDED FOCUS

Zero Focus (0mm (on the surface))

Challenges

  • Heat builds up quickly — risk of discoloration
  • Corrosion resistance can drop with excessive heat

Pro Tips

  • Control heat input to prevent corrosion issues
  • Zero Focus for clean cosmetic welds
  • Argon shielding preserves corrosion resistance

Galvanized Steel

Moderate

Zinc coating reflects and vaporizes — needs high density to break through.

RECOMMENDED FOCUS

Zero Focus (0mm (on the surface))

Challenges

  • Zinc vapor causes porosity and spatter
  • Coating reflects the initial beam contact

Pro Tips

  • Use Zero Focus to break the zinc layer with high density
  • Defocus slightly (+1 mm) for thicker zinc coatings
  • Ensure good ventilation for zinc fumes

Aluminum Alloy

Hard

High reflectivity, high thermal conductivity. Difficult to weld.

RECOMMENDED FOCUS

Zero Focus (0mm (on the surface))

Challenges

  • Reflective surface bounces the beam at low power
  • Heat dissipates fast — needs more power
  • Porosity from hydrogen in the weld pool

Pro Tips

  • Zero Focus with high power density
  • Use Wobble mode to stir the pool and reduce porosity
  • Requires higher power and auxiliary gas (Argon)
  • Pre-clean the surface — aluminum oxide reflects the beam

Copper

Extreme

Extreme reflectivity and conductivity. Hardest to weld.

RECOMMENDED FOCUS

Zero Focus (0mm (on the surface))

Challenges

  • Reflects ~95% of laser energy at room temperature
  • Heat dissipates faster than aluminum
  • Strict focus requirements

Pro Tips

  • Strictly Zero Focus — any defocus loses density needed to melt copper
  • Requires higher power and auxiliary gas (Oxygen or Nitrogen)
  • Use a high-power laser source (≥1500 W recommended)
  • Pre-heat sometimes needed for thick copper sections

Applications

Right focus for the right job.

From thin cosmetic sheet work to full-penetration thick plate, the best focus depends on what you're trying to achieve.

01

General Thin Sheets

Smallest spot, highest surface density.

USE FOCUS

Zero Focus (0mm (on the surface))

Thin material doesn't need deep penetration — Zero Focus keeps the energy concentrated at the surface for fast, clean welds.

Considerations

  • Use high travel speed to avoid burn-through
  • Zero Focus at low power
  • Backing gas recommended for full-penetration thin welds
02

Medium Thickness

Balanced settings for general fabrication.

USE FOCUS

Zero Focus (0mm (on the surface))

Mid-range material responds well to Zero Focus with slightly higher power and slower travel than thin sheets.

Considerations

  • Zero Focus with moderate travel speed
  • Nitrogen shielding for cleaner welds
  • Move to Negative Focus if penetration is shallow
03

Thick Plates

Max penetration depth, wider weld pool.

USE FOCUS

Negative Focus (-2mm to -4mm)

Thick material needs the beam to drill below the surface — Negative Focus uses the keyhole effect to push energy into the depth of the joint.

Considerations

  • Negative Focus for deep keyhole penetration
  • Enable Wobble mode to stir the pool and reduce porosity
  • Use higher power and slower travel speed
04

Cosmetic Weld

Final cap pass — smooth surface, no deep penetration needed.

USE FOCUS

Positive Focus (+2mm to +5mm)

Positive Focus widens the melt pool on the surface for a smooth, spatter-free finish. Best for visible welds and final pass overlay.

Considerations

  • Positive Focus (+2 mm to +5 mm) for wider melt
  • Lower power than primary weld
  • Argon shielding preserves the surface finish
05

Full Penetration

Complete through-weld on both sides of the joint.

USE FOCUS

Negative Focus (-2mm to -4mm)

Negative Focus concentrates energy at depth to drive the weld through the entire thickness — required when both sides must be fused.

Considerations

  • Negative Focus with high power
  • Backing gas (Argon) prevents oxidation on the underside
  • Verify penetration visually before production runs

Assistant

Ask the focus expert.

Type a quick question — about a material, a common problem, or a technique tip — and get an instant answer from our curated expert knowledge base.

  • 01Material-specific focus recommendations
  • 02Common problem troubleshooting (spatter, porosity, penetration)
  • 03Technique tips (Wobble mode, gap filling, shielding gas)

Focus Assistant

Keyword-based expert Q&A

Ask a quick question about laser welding focus — materials, common problems, or technique tips.

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