Consequences of Using Inferior Protective Lens for Laser Cutting Head

The use environment of the cutting head in the laser cutting machine is very harsh, so in order to protect the internal optical path and core components, especially the expensive parts such as the focusing lens, the cutting head must be equipped with a protective lens.

Dust and splashes are generated on the surface of the workpiece during the cutting process, if it enters into the cutting head, it will cause serious damage to the focusing lens, the protective lens can block these dust and splashes.


The cleanliness of the protective lens directly affects the processing performance and quality of the laser cutting machine. If the lens is dirty, it will not only affects the cutting effect, but also cause the internal parts of the cutting head and the laser output head to burn out, so it needs to be cleaned and replaced from time to time.

Protective lens processing has special technological requirements, from the selection of base material, processing accuracy, surface defects, coating, stability, mechanical properties, (specific gravity, brittleness, tensile strength, compressive strength, hardness) preparation of materials in the process flow, (different processing requirements for CG→SC→PO→DC→CO) the finished products can only be launched after strict quality inspection.

In order to reduce the cost, the inferior protective lens uses mediocre base materials. The coating process is not guaranteed, the light transmittance is poor, not heat-resistant, easy to break, cannot withstand the penetrating power of the laser, causing the lens to blast holes, and the powder particles of the broken lens will pollute the entire cutting head, the core high-value components including the focusing lens and sensor are damaged. The maintenance cost will be as high as 40% of the price of the new cutting head.

Therefore, we encourage our customers to purchase laser accessories from the official channels of manufacturers to avoid losses!
The following are the adverse effects that inferior protective lens likely to cause:

Thermal lens effect
The poor quality protective lens will increase the absorption rate of the laser. After a long time of continuous exposure, the temperature will increase and cause thermal deformation which will cause the thermal lens effect. When the power is higher, or when processing highly reflective materials, the thermal expansion of the optical component will be faster, and the thermal lens will be more obvious.

(1) When cutting stainless steel, the thermal lens effect will cause the cutting surface to be inconsistent, more dross, and even continuous cutting problems.
(2) When cutting carbon steel, the thermal lens effect will cause more and more slag at the bottom and continuous cutting problems.

Protective lens burn through
After the inferior protection lens is installed, the sealing performance of the cutting head will be poor which is easy to cause dirt and damage, causing the back reflective light to burn through the protective lens.

Focusing lens burning point
After the protective lens is burned, it will also cause burning spots on the surface of the focusing lens, resulting in particulate smoke rising and polluting the lower surface of the focusing lens, installation components and sealing ring, require deep cleaning and replacement, otherwise it will affect processing.

Output head burnout
When the internal optical components of the cutting head such as the focusing lens and collimator are damaged, the optical path will be abnormal, which will cause abnormal heating of the back reflective light focusing window, and finally burn out the QBH crystal, the entire laser output head needs to be replaced.