Workshop 3: 🔗 Laser Welding¶

Industrial Workshop 3 of 7

Laser Welding

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Workshop Brief¶

Weld two 2 mm aluminium sheets edge-to-edge using a fibre laser. Aim for full-depth penetration with a smooth bead and no gas-porosity voids trapped in the weld.

Specifications: Material: Al 2 mm + 2 mm · Full penetration · Zero porosity

Process Theory¶

Laser welding melts a narrow, deep region along the joint line, which then re-solidifies to fuse the two parts. Aluminium is particularly prone to gas porosity because of its high thermal conductivity (requiring higher power density to achieve melting) and its tendency to dissolve hydrogen in the melt pool, which can be trapped as bubbles during rapid solidification.

Laser power and welding speed jointly determine whether the weld achieves full penetration through both 2 mm sheets: insufficient power or excessive speed under-melts the joint, while excessive power or very slow speed can cause keyhole instability and porosity.

The focus offset (distance of the beam waist from the material surface) affects the shape of the melt pool and the keyhole: focusing exactly at the surface gives maximum power density at the top, while a small positive offset can help maintain a more stable, deeper keyhole for full-penetration welds.

Process Parameters¶

Parameter	Range	Unit
Laser power	400 – 3000	W
Welding speed	200 – 2500	mm/min
Focus offset (0 = surface)	−3 – +3	mm

Procedure¶

Record the precision score at the default power, speed and focus offset.
Vary laser power alone and record the precision score at each value.
Repeat, varying welding speed alone, then focus offset alone.
Identify the combination giving full penetration, minimal porosity, and a 100% precision score.

Observation Table¶

Table: Effect of fibre-laser welding parameters on weld quality

Trial	Power (W)	Speed (mm/min)	Focus offset (mm)	Precision score (%)	Verdict
1
2
3
4
5
6
7
8

Graph¶

Plot Precision score (%) (y-axis) against Laser power (W) (x-axis).

Expected trend: a rising trend up to full penetration, then a fall-off as excess power induces porosity/instability.

Precision score vs laser power, holding speed and focus offset fixed

📈 Graph paper / plot area — attach printed or digital graph here

Calculation¶

Estimate the linear energy input (Power / Speed) for each trial and relate it qualitatively to penetration depth.
State the final optimized (Power, Speed, Focus offset) combination reaching certification.

Result¶

Table: Optimized parameter set for laser welding

Power (W)	Speed (mm/min)	Focus offset (mm)	Final precision (%)	Certified? (Y/N)
1

Precautions¶

Remember that aluminium's high thermal conductivity and reflectivity generally require higher power density than steel for an equivalent weld.
Explore both positive and negative focus offsets, not only the surface (0 mm) setting.