6 Common Causes of Protective Lens Damage in Laser Welding Machines

In the daily use of laser welding machines, the protective lens is one of the most easily damaged and also one of the most critical optical components. It is located at the very front of the welding head and directly bears the impact from high-energy laser beams and welding spatter, serving to protect the focusing lens and reflection mirrors. However, many users often find a problem during use: the lens was just replaced and shortly afterwards it burned out again!

In fact, most lens burnouts are not caused by equipment quality issues, but by improper operation or nonstandard maintenance. This article will detail six common causes of protective lens burnout in laser welding machines and their prevention methods, helping you effectively extend equipment service life and reduce maintenance costs.

1.Spatter contamination causes lens damage

Spatter is one of the most common causes of lens damage during laser welding. When the welded material surface has rust, oil, or oxidation layers, the laser irradiation will produce explosive high-temperature spatter. These metal particles fly out at high speed and can easily enter the optical cavity from the gun nozzle, striking the protective lens directly and causing coating ablation or mirror surface cracking.

Prevention suggestions:

Clean the workpiece before welding: remove oil, rust, and contaminants.

Adjust the welding angle so that the spatter direction avoids the optical path.

Use a welding gun with an anti-spatter nozzle or a gas protection system.

2.Dust and foreign matter cause lens damage

Dust is often overlooked, but its harm is great. When opening the gun optical path or replacing the lens, if the environment has a lot of dust (especially near fans or vents), these fine particles will enter the cavity. When the laser irradiates the dust, localized high-temperature spots form, gradually ablating the coating layer and causing the lens to yellow, char, or crack.

Prevention suggestions:

Keep the environment clean and away from air sources when replacing the lens;

After opening the optical cover, immediately seal the opening with masking tape to prevent dust ingress;

If the workshop environment is poor, consider setting up a dedicated dust-free replacement area.

3.Contamination from improper replacement procedures

Many operators habitually pick up the lens directly with their hands or do not wear gloves when replacing it. Human hands contain oils and moisture; if they touch the lens, these will carbonize under high-energy laser irradiation and form black spots. Over time, the lens coating will be damaged and its transmittance will decrease, eventually leading to burnout.

Prevention suggestions:

Wash hands and wear dust-free gloves before replacing the lens, or strictly avoid touching the lens surface during replacement;

If possible, use a dedicated vacuum pen or clean tweezers for handling;

During replacement, strictly prevent the lens from contacting other metal surfaces or hard objects to avoid scratching.

4.Delayed replacement of lenses triggers chain reactions

Some users think that a slightly yellowed or lightly scratched lens can still be used for a few more days. However, a damaged lens causes the laser to reflect and scatter inside it, and part of the optical energy will be reflected back into the optical path, heating the focusing lens, collimating lens and other internal optical components. Over time, the entire optical path system will be affected and burned out.

Prevention suggestions:

Establish a lens inspection system and regularly check transmittance or observe the beam spot;

If yellowing, black spots, or unstable welding beam are observed, replace the lens immediately;

It is recommended to keep spare lenses with the equipment for timely replacement.

5.Improper welding technique causes reflective burns

The correct welding angle is usually around 45°. This angle both reduces spatter rebound and prevents reflected light from directly hitting the lens. If welding is done vertically, especially when processing highly reflective materials (such as stainless steel or aluminum alloys), reflected light can return directly into the gun cavity, heating the lens and ultimately causing coating ablation or even cracking.

Prevention suggestions:

Maintain a proper welding angle when welding (within the range of 30°–60°);

For highly reflective materials, reduce power appropriately or use anti-reflective lenses;

Regularly check whether the nozzle and the optical path center are coaxial.

6.Lens quality issues

Even with proper operation, if the lens quality is poor, burnout is still unavoidable. Some low-price lenses have only about 80% transmittance; the remaining 20% of energy is absorbed as heat, causing the lens to heat continuously. When the temperature becomes too high, the coating will delaminate, and the lens will yellow or even crack.

Prevention suggestions:

Use high-quality lenses with ≥99% transmittance and wavelengths matched to the laser;

Choose anti-reflection coated lenses from original manufacturers or certified suppliers;

Avoid purchasing unmarked or cheap inferior optical components.

How to extend the service life of protective lenses

Regular maintenance: Inspect lens surfaces weekly for burn marks or debris.

Keep the optical path clean: Prevent fumes, dust, and oil from entering.

Use quality consumables: Select stable shielding gases and welding wire.

Proper storage: Store unused lenses in dustproof, moisture-proof containers.

Standardized operation: Maintain correct welding posture and angles.

Although the protective lens seems like a small and ordinary accessory inside the welding head, it bears the important responsibility of protecting the entire optical system. Replacing a burned lens may not cost much, but if the focusing lens is damaged, losses can reach tens of thousands of yuan. Only by understanding the root causes of lens burnout and mastering scientific maintenance methods can you truly ensure the stability and long-term performance of laser welding equipment.

Want your laser welding equipment to weld more stably and last longer?

ZS Laser supplies original high-quality protective lenses, focusing lenses, and full machine maintenance solutions, and offers customers free technical consultation and welding process optimization advice. Contact us now to keep your laser welding machine operating at its best.