Laser welding joins metal parts by focusing a concentrated laser beam onto the joint. The beam melts a narrow zone of material on both sides of the seam, the molten metal fuses and solidifies, and the parts become one. Because the energy is delivered to a very small spot, the surrounding material heats up far less than with arc welding — which means less distortion, a narrower heat-affected zone and a cleaner seam that often needs little or no grinding. It is especially well suited to thin sheet, stainless steel and precise sub-assemblies, and it is most consistent when the welding head is guided by a robot.

Below we explain how the process works, how it compares with TIG and MIG, where its limits are, and how we use it in our own robotic welding cell in Prague.

How laser welding works

A modern laser welding system has three parts: a laser source, a delivery path and a welding head.

The source. Most industrial laser welding today uses a fibre laser, in which the beam is generated inside an optical fibre. Fibre lasers are compact, efficient and deliver a beam that can be focused very tightly.
The delivery. The beam travels through a flexible fibre-optic cable to the welding head. That is what makes it practical to mount the head on a robot arm.
The head. Optics focus the beam onto the joint. Shielding gas protects the molten pool from the atmosphere, and depending on the joint, filler wire can be fed into the weld.

Two welding modes

Laser welding works in two broad regimes:

Conduction mode. At lower power density, the surface melts and heat spreads into the material by conduction. The result is a shallow, wide, very smooth seam — good for visible joints and thin material.
Keyhole mode. At higher power density, the metal vaporises locally and forms a narrow cavity — the keyhole — that lets the beam penetrate deep into the joint. The result is a deep, narrow weld with a small heat-affected zone.

Which mode is used is a matter of power, focus and travel speed, and it is chosen for the joint and material at hand.

Laser welding vs TIG and MIG

Each process has its place. The comparison below is qualitative — real values depend on material, thickness, joint design and equipment.

	Laser welding	TIG	MIG / MAG
Heat input	Low, concentrated	Moderate	Higher
Distortion of thin sheet	Low	Moderate	Higher
Seam appearance	Narrow, clean	Very clean when done by a skilled welder	Wider, may need finishing
Post-weld grinding	Minimal	Moderate	Often required
Spatter and UV	No arc UV, no spatter	UV from the arc	UV and spatter
Joint fit-up required	Tight	Tolerant	Most tolerant, bridges gaps
Filler consumption	Low	Moderate	High
Suited to	Thin sheet, stainless, precise sub-assemblies	High-quality manual welds	Thicker sections, high deposition
Automation	Very well suited to robots	Possible	Widely automated

Where laser welding wins

Thin stainless sheet. Low heat input means panels stay flat and the seam discolours less. Less straightening, less grinding, less rework.
Visible seams. A narrow, even seam that needs minimal finishing.
Precise sub-assemblies. When the parts come from an accurate sheet-metal chain, the fit-up is good enough for the laser to do its best work — and the assembly keeps its dimensions after welding.
Repeatability. On a robot, every weld follows the same path at the same speed. That consistency matters for parts in long cyclic-load service.

Where it does not

An honest article has to say where laser welding is the wrong choice:

Poor fit-up. The beam is narrow. Wide or uneven gaps that a MIG welder bridges easily can be a problem for a laser. Laser welding rewards accurate parts and punishes sloppy ones.
Thick sections and heavy fabrication. For very thick plate or high-deposition work, arc processes are often more practical.
Highly reflective metals. Materials such as aluminium and copper reflect much of the beam and need appropriate parameters and experience.
Equipment cost and safety. Laser systems cost more than arc welders, and the laser itself is a serious hazard that has to be managed under laser-safety rules. The absence of arc UV and spatter does not make the beam harmless.

How strong is a laser weld?

Strength depends on the joint design, penetration, material and the quality of execution — not on the process name alone. A well-designed, fully fused laser weld can be a fully load-bearing structural joint; a poorly fitted one will not be. We therefore do not quote generic strength figures. We design the joint for the load case and build welded structural sub-assemblies for ten-plus years of cyclic loading.

Why a robot should hold the torch

A laser is precise, but only as precise as the path it follows. That is why our laser welding is robotic.

In our cell, an IPG LightWELD XR fibre laser welding head is carried by a FANUC CRX collaborative robot. Some of our CRX cobots ride a seventh-axis linear track, so one robot covers a whole work envelope — long frames and large panels included. A 3D camera guides the path, and welds can run supervised or autonomously. The robot holds the exact path at the exact speed, every time — which is where the low distortion and repeatability come from.

The same cobots do more than weld: they assemble sub-assemblies automatically and tend the Mazak CNC and other machines. A welded frame can therefore move through bending, welding and machining without leaving the same team. Details are on the technology page.

Laser cleaning before and after the weld

Weld quality starts before the weld. Oils, oxides and surface films on the joint can cause porosity and an uneven seam. Our workflow includes laser pre-cleaning of the joint and laser post-cleaning of the seam as part of the same process, so the surface is prepared and the result is finished without a separate trip to another workstation.

On stainless steel, weld discolouration and surface oxides are a recurring topic. One of our reference projects is a handheld electrochemical cleaning pistol designed for exactly that job — you can find it on the work page.

Designing a part for laser welding — checklist

Plan for tight fit-up. Keep gaps small and consistent; accurate bending and punching upstream pay off here.
Choose the joint type early. Butt, lap, fillet and edge joints behave differently; tell us the load the joint carries.
Leave access for the head. The robot needs a line of sight and room to move along the seam.
Mark visible seams. If a seam is cosmetic, say so — it changes how we set it up and finish it.
Think about fixturing. Self-locating features such as tabs and slots make assemblies easier to position and reduce fixture work.
State the material and surface condition. Stainless, mild steel, coated or raw — each needs its own parameters.

FAQ

What is laser welding used for?

It is widely used wherever precise, low-distortion joints are needed — thin sheet assemblies, stainless enclosures and frames, structural sub-assemblies and parts with visible seams. We use it for frames, panels and sub-assemblies of machines we build.

Is laser welding stronger than TIG or MIG?

Not by definition. Strength comes from joint design, penetration and execution. A laser weld can be fully load-bearing; the advantage is low distortion and repeatability, not a stronger label.

Does laser welding need filler wire?

Not always. Some joints are welded autogenously, without filler; others use wire. Laser welding generally consumes less filler material than arc welding.

Can laser welding be used on thin stainless steel?

Yes — it is one of its strongest applications. Low heat input keeps thin panels flat and limits discolouration.

Do you weld single parts or only series?

Both. Our cell is set up for single units and small series, alongside the rest of our capabilities.

Next step

If you have a welded assembly that has to stay flat, look clean and carry load for years, send us the model and tell us what it has to do. We will look at the joints, the fit-up and the sequence, and tell you whether laser welding is the right process — or not. Contact us.

Laser welding explained: how it works, how strong it is, and when a robot should hold the torch