Factors Affecting the Weld Bead Width in Laser Welding Machines
The weld bead width in laser welding is influenced by multiple factors, which can be categorized into laser parameters, optical system settings, process conditions, material properties, and other external factors. Below is a detailed breakdown:
1. Laser Parameters
(1) Laser Power
Higher power → Wider weld (more heat input, larger melt pool).
Lower power → Narrower weld (less penetration, possible lack of fusion).
(2) Beam Mode (Beam Quality)
TEM00 (Gaussian beam) → Narrow, deep welds (high energy concentration).
Multi-mode beams → Wider, shallower welds (energy more dispersed).
(3) Pulse Parameters (for Pulsed Lasers)
Higher frequency → Wider weld (more overlapping pulses).
Longer pulse width → Wider weld (extended heat input).
Higher duty cycle → Wider weld** (longer energy exposure).
2. Optical System Parameters
(1) Focus Spot Diameter
Larger spot → Wider weld (lower energy density).
Smaller spot → Narrower weld (higher energy concentration).
(2) Defocusing (Beam Position)
Positive defocus (above workpiece) → Wider weld.
Negative defocus (below workpiece) → Wider weld.
Zero defocus (on surface) → Narrowest weld.
(3) Focal Length of Lens
Longer focal length → Larger spot → Wider weld.
Shorter focal length → Smaller spot → Narrower weld.
3. Process Parameters
(1) Welding Speed
Higher speed → Narrower weld (less heat input).
Lower speed → Wider weld (more heat accumulation).
(2) Shielding Gas
Gas type (Ar, He, N₂) → Affects plasma suppression and cooling rate.
Higher gas flow → Slightly narrower weld (faster cooling).
(3) Wire Feeding (for Laser Wire Welding)
Thicker wire → Wider weld (requires more energy to melt).
Higher wire feed rate → Wider weld (more filler material deposited).
4. Material Properties
(1) Thermal Conductivity
High conductivity (e.g., Cu, Al) → Narrower weld (heat dissipates quickly).
Low conductivity (e.g., stainless steel) → Wider weld (heat stays localized).
(2) Material Thickness
Thicker materials → Wider weld (higher power needed).
Thinner materials → Narrower weld (less energy required).
(3) Surface Condition
Oxides, coatings, or contaminants → Affect laser absorption → Irregular weld width.
5. Other Factors
(1) Joint Configuration
Butt, lap, or fillet joints → Different heat dissipation → Affects weld width.
(2) Beam Oscillation (Weaving)
Oscillating laser beam → Wider weld (used for gap bridging or thick plates).
(3) Environmental Conditions
Ambient temperature/humidity → Minor influence on cooling rate.
Summary: How to Control Weld Bead Width?
| Goal | Adjustment Method |
| Increase width | ↑ Power, ↓ Speed, ↑ Defocus, ↑ Spot size, Use thicker wire, Oscillate beam |
| Decrease width | ↓ Power, ↑ Speed, Zero defocus, ↓ Spot size, Use thinner wire, TEM00 mode |
For optimal results, Design of Experiments (DOE) is recommended to fine-tune parameters based on material and application requirements.
---------Victor Feng
Rayther Laser