Ring Beam Laser Cutting for Thick Steel Kerf Control
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Solution Overview
Problem
Fiber lasers with a one-micrometer waveband, when used for cutting thick mild steel sheets with oxygen assist gas, result in excessive burning and poor kerf control due to high energy density, making it difficult to achieve the same cutting quality as CO2 lasers.
Innovation Solution
Forming the laser beam into a ring beam with an outer diameter of 300 µm to 600 µm and an inner diameter ratio of 30% to 70%, which disperses energy density and allows the use of oxygen assist gas without self-burning, similar to CO2 laser cutting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a one-micrometer waveband laser beam (fiber laser) is used with oxygen assist gas to cut a mild steel sheet, then optical energy absorptance increases, but melt width on the top face widens excessively causing poor kerf control
Solution Approach 1:
The laser beam is segmented from a concentrated spot into a ring-shaped beam with inner and outer diameters. This segmentation distributes the energy across an annular region rather than concentrating it at a single point, reducing peak energy density while maintaining total energy input. The ring beam structure effectively divides the energy delivery zone to prevent excessive localized heating and self-burning.
Solution Approach 2:
The invention applies local quality by creating a non-uniform energy distribution pattern where the ring beam provides different energy densities at different radial positions. The inner region has reduced energy density to prevent self-burning, while the outer ring maintains sufficient energy for effective cutting. This localized energy modulation allows simultaneous achievement of good kerf control and adequate cutting performance.
2Power
If a one-micrometer waveband laser beam is condensed to a small spot diameter for required cut width, then energy density increases, but self-burning occurs expanding melt width wider than required cut width
Solution Approach 1:
The concentrated spot beam is segmented into a ring beam structure that separates the high-energy center from the energy delivery zone. This segmentation eliminates the problematic concentration of energy at the beam center that causes self-burning, while maintaining sufficient energy density in the annular region for effective cutting.
Solution Approach 2:
The ring beam structure acts as an intermediary between the laser source and the workpiece, modifying the energy distribution pattern. It transforms the problematic concentrated energy profile into a distributed annular profile, mediating the interaction between laser energy and material to prevent harmful self-burning while maintaining cutting effectiveness.
3Productivity
If fiber laser with high energy density is used for cutting thick mild steel sheets, then cutting speed improves, but quality of cut work deteriorates due to excessive burning
Solution Approach 1:
The ring beam segmentation allows the system to maintain high total power for fast cutting while distributing energy to avoid localized overheating. This enables high productivity through efficient energy utilization without sacrificing quality, as the segmented energy distribution prevents excessive burning and kerf widening.
Solution Approach 2:
The invention changes the spatial distribution parameter of the laser beam from a concentrated Gaussian profile to an annular ring profile. This parameter change fundamentally alters the energy-matter interaction, enabling high cutting speeds while maintaining quality by preventing the thermal conditions that lead to excessive burning and poor surface quality.
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 approach effectively suppresses self-burning and maintains proper kerf control, enabling cutting of thick steel sheets with improved surface quality and reduced energy density, comparable to CO2 laser cutting.
Implementation Method 1
the laser beam is condensed through a condenser lens into a spot of 100 μm (micrometers) to 500 μm (micrometers) to increase energy density and instantaneously heat the work to a metal melting point of 1500 degrees or over
Implementation Method 2
When cutting a metallic work with a laser beam, the laser beam is condensed through a condenser lens into a spot
Implementation Method 3
an oxygen gas is used as the assist gas to generate oxidization reaction heat and utilize the heat as well for cutting the work
Implementation Method 4
generate oxidization reaction heat
Implementation Method 5
forming a laser beam of the fiber laser into a ring beam and cutting a work with the ring beam provide the same effect as that provided by the CO2 laser
Data Source
Figure 1(A)~1(B)
Figure 2(A)~2(B)
Figure 3(A)~3(B)
AI summary
A laser cutting method and a laser cutting apparatus cut a metallic work with a laser beam of a one-micrometer waveband. The method and apparatus carry out the laser cutting of the work with a ring beam RB passed through a focus position of a condenser lens 13 and having inner and outer diameters that tend to expand. The outer diameter of the ring beam is in a range of 300 µm (micrometers) to 600 µm, an inner diameter ratio of the same is in a range of 30% to 70%, and a focal depth of the condenser lens is in a range of 2 mm to 5 mm.