What is High Reflectivity Material?

Generally, the high reflectivity material refers to the low absorption rate of near-infrared laser due to the small resistivity of the processed material and the smoother surface, as shown in the figure, the absorption coefficient of common metal elements, which leads to a large amount of laser reflection, and because most lasers are used in scenarios perpendicular to the material or a small amount of inclination which leads to the return laser re-enter the output head, or even part of the return optical coupling into the energy transfer fiber, along the fiber reverse transmission to the laser internal will get the core components high temperature until damage it.

Why Raycus Fiber Laser Can Cut High Reflectivity Materials?

For processing high reflectivity material, welding, and cutting, once there is too much laser beam return by the reflective material, obviously a certain risk to damage the laser head and the laser source. And this risk of a high-power laser source is much higher than a low-power laser source.

In cutting high reflectivity materials, in the case of material not piercing though, there will be higher power return to the laser internal, damage the laser source. So Raycus R&D team has designed a four-stage anti-reflective laser protection design of the fiber laser source, and enhance it with laser light monitoring functions to ensure real-time protection of the laser source to make it stable cutting high reflectivity materials.

1. What is the Four levels of Anti-Reflective Laser Protection Design?

The QBH, QD, and QP fiber output heads designed Raycus with the function to convert the reflective laser beam into absorbable light and heat, and use water cooling the laser head to absorb the heat away, to avoid the impact of the laser head.

For the laser cutting machine, the return laser will firstly affect the output fiber optical cable head, making the output optical cable at risk of heating or even damage.

In order to ensure the safety of the output fiber optical cable, Raycus has integrated a level of return laser stripping device inside the output optical cable, as shown in the figure.

The anti-reflective design of the cable output can strip most of the return laser which will be taken away by circulating cooling water from the water chiller, reducing the damage to the internal laser fiber optical device.

2. Two-stage Anti-reflective Design in Beam Combining Module

The multi-module high-power laser source is designed with the multi-unit module, when cutting highly reflective materials, after the return light passes through the fiber optical cable at the first level of anti-reflection design, there may still be part of the laser light through the output optical cable reverse transmission to the inside of the beam.

Therefore, considering the safety and reliability, the two-stage anti-reflection protection design was added inside the combiner of Raycus laser source, as shown in the figure, using step-by-step stripping of return laser light to ensure the safety of anti-reflection protection optics and reduce the impact of return laser light on the laser optical parts.

Anti-high Reflection Design of Laser Module Unit

Due to the existence of an optical resonant cavity inside the module unit, once the low power return laser enters the module unit and is continuously amplified by the resonant cavity, it will seriously affect the optical stability of the laser and increase the risk of damage to the laser source. In order to further improve the stability and reliability of the laser during high reflection cutting, the anti-reflection device has to add to protect each module unit.

Anti-reflecting Software Monitoring (Keep Updating)

Although the anti-reflective device can ensure that the laser can still work normally without damage within a certain return laser power threshold, still there will be a risk of damage in case the threshold is exceeded, therefore, in order to ensure that the laser source can be protected when the return laser is too high, the multi-module high-power laser products incorporate multiple high-reflective software monitoring protection designs.

Anti-reflecting software monitoring is a function of monitoring laser operation status when the laser is processing high-reflection materials and the strong return reflection generated enters the laser optical system, then warning stop to protect the fiber laser source.

• Monitoring of Fiber laser optic cable

When the return laser light power is higher enough, some of the laser light will be returned to the fiber laser output optical device, through the study and research of the return laser transmission problems and monitoring function integration technology, Raycus enable fiber optical cable temperature monitoring, output laser beam monitoring and return laser light monitoring. Once the return laser power exceeds the range that the laser can withstand, the laser source will be shut down alarming in time to ensure that the laser source will not be damaged, and to remind the user that there is an abnormality during the cutting process.

• Monitoring of Module & Combiner

Considering that there are two types of return lasers, core laser, and cladding laser, in addition, to enable monitoring of the fiber laser optic cable, Raycus also designed a sensor to detect if the laser power is higher in module and combiner. It will be monitored not only the cladding laser but also the core laser. The laser source will be turned off and alarming to avoid the risk of damage to the laser source caused by the core return laser.

Laser cutting high reflective aluminum with clean edge
Not cutting through test function of Anti-reflective laser protection

How thick is 3kw 6kw Fiber Laser Cutting High Reflectivity Material?

Engineer Advice for Laser Cutting of High Reflectivity Materials.

(1) Don’t use the max cutting capacity for cutting the high reflectivity material like brass, purple copper, mirror stainless steel, silver, and gold, etc. Slow down the cutting speed.

(2) When you cutting Purple copper, the assistant gas should be oxygen, not nitrogen or air.

Please stop and check immediately if there is dust in the protection mirror, Not piercing through the high reflectivity materials, or piercing through but not cutting through the material.