UV-Filtering Optical Elements for Stable High-Power Laser Cutting
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Solution Overview
Problem
High-power laser cutting processes (>6 kW) using solid-state or diode lasers often experience process disruptions due to the formation of metal vapors in energetically intensive states, leading to critical heating of optical elements in laser processing heads, which can cause a shift in the focal position and disrupt the cutting process.
Innovation Solution
The implementation of optical elements with coatings that reflect or absorb radiation components with wavelengths below 400 nm, preventing these from reaching the other optical elements and thus minimizing heating, includes a reflective coating for wavelengths below 400 nm and an absorbent coating for UV radiation, ensuring the optical elements remain cool and maintain a stable focal position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical elements are used in high-power laser processing heads, then laser beam transmission is enabled, but the optical elements heat up due to absorption of UV process radiation below 400 nm, causing focal position shift
Solution Approach 1:
A UV-reflecting coating is applied to the optical element to act as an intermediary that reflects UV radiation below 400 nm while transmitting the laser beam wavelength. This coating prevents direct absorption of harmful UV radiation by the optical element material, thereby preventing heating and focal position shift while maintaining laser transmission capability
Solution Approach 2:
The optical properties of the optical element are modified by applying a coating with specific reflective and transmissive parameters. The coating is designed to reflect radiation in the wavelength range below 400 nm while transmitting the laser beam wavelength, changing the optical element's interaction with different wavelength components of the radiation
2Productivity
If high laser power is used for cutting, then cutting speed and productivity increase, but process disruptions occur due to formation of energetically intensive metal vapors and plasma
Solution Approach 1:
The harmful UV radiation emitted by energetically intensive metal vapors during high-power laser cutting is converted from a harmful factor into a manageable parameter by using a UV-reflecting coating. The coating reflects this radiation away from the optical elements, allowing high-power cutting to proceed without the detrimental effects of UV absorption and heating
Solution Approach 2:
The UV-reflecting coating provides preliminary protection against UV radiation before the radiation can cause heating and focal position shift. By reflecting the UV radiation at the optical element surface, the coating prevents the subsequent harmful effects of energy absorption
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively prevents process disruptions by maintaining the stability of the focal position during high-power laser cutting, enhancing the overall process stability and reducing the need for control interventions, even during long cuts.
Implementation Method 1
The optical element has a coating that transmits the laser wavelength of the laser beam and is highly reflective for radiation components of the process radiation with wavelengths of less than 400 nm. The interfering process radiation is reflected back at the optical element in the direction of the workpiece or process zone
Implementation Method 2
The optical element has a coating that is reflective for the laser wavelength of the laser beam and highly absorbent for wavelengths of the process radiation of less than 400 nm
Data Source
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AI summary
In a laser machining head (1) for laser machining workpieces (2) using a laser beam (3), an optical element (6) arranged in the beam path of the laser beam (3) is designed such that radiation components with a wavelength of less than 400 nm are filtered out of a process radiation (7) coming from the workpiece (2). Preferably, the at least one optical element (6) has a coating (8) which is transmissive for the laser wavelength of the laser beam (3) and is highly reflective for wavelengths of the process radiation (7) of less than 400 nm.