Beam Shaper Wavefront Mixing for Smooth Thick-Sheet Laser Cutting

Solution Overview

Problem

Laser cutting of thick metal sheets often results in corrugated surfaces due to factors like hot spots, turbulences, and uncontrolled reaction fronts, leading to reduced cutting quality, especially for workpieces thicker than 15 mm.

Innovation Solution

A beam shaper that includes a first beam shaping section for shaping the central part of the laser beam to have spherical wave fronts and a second section for shaping the peripheral part to have parallel wave fronts, which are incoherently superimposed to create a homogeneous intensity distribution, stabilizing the cutting process and reducing surface corrugations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If laser beam is used for cutting thick metal sheets, then cutting capability is improved, but surface corrugation increases

Engineering Contradiction:

Improvecutting depthVSAvoidsurface quality

Core Design Contradiction:

Length of moving objectVSManufacturing precision

Solution Approach 1:

The patent applies local quality by creating a non-uniform beam intensity distribution where the central region has lower intensity and the peripheral region has higher intensity. This localized differentiation allows the beam to interact differently with various parts of the material, preventing hot spot formation in the center while maintaining effective cutting at the periphery, thus reducing surface corrugation while enabling deep cuts.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs dynamics by continuously adjusting the beam parameters (intensity distribution, focal position) during the cutting process. The beam intensity profile is dynamically optimized to match the varying requirements at different cutting depths and positions, allowing adaptation to prevent hot spot formation and surface corrugation as the cut progresses through thick material.

Inventive Principle:

Principle #15Dynamics

2Productivity

If high laser power is used to cut thick workpieces, then cutting speed is improved, but hot spots are formed

Engineering Contradiction:

Improvecutting speedVSAvoidhot spots

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by creating a non-uniform beam intensity distribution where the central region has lower intensity and the peripheral region has higher intensity. This localized differentiation allows the beam to interact differently with various parts of the material, preventing hot spot formation in the center while maintaining effective cutting at the periphery, thus reducing surface corrugation while enabling deep cuts.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent applies partial action by concentrating the laser energy in specific peripheral regions rather than uniformly distributing it across the entire beam area. This selective energy application ensures that sufficient power is delivered to drive the cutting reaction without excessive energy input that would cause hot spots, achieving an optimal balance between cutting speed and temperature control.

Inventive Principle:

Principle #16Partial or excessive action

3Measurement precision

If conventional beam shaping is used, then beam focus is improved, but intensity uniformity deteriorates

Engineering Contradiction:

Improvebeam focusVSAvoidintensity distribution

Core Design Contradiction:

Measurement precisionVSStability of the object's composition

Solution Approach 1:

The patent applies local quality by creating a non-uniform beam intensity distribution where the central region has lower intensity and the peripheral region has higher intensity. This localized differentiation allows the beam to interact differently with various parts of the material, preventing hot spot formation in the center while maintaining effective cutting at the periphery, thus reducing surface corrugation while enabling deep cuts.

Inventive Principle:

Principle #3Local 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

The solution achieves smooth cut surfaces on metal sheets thicker than 15 mm by maintaining a stable and uniform energy distribution, reducing surface corrugation amplitudes and preventing hot spots, thereby enhancing the overall cutting quality.

Implementation Method 1

a second beam shaping section (3) for shaping a peripheral part of the laser beam such that the laser beam includes second wave fronts which are at least partially parallel and at least partially incoherently superimpose the first wave fronts

Methodology Applied

Scientific EffectIncoherent superposition:

Implementation Method 2

a first beam shaping section (2) for shaping a central part of the laser beam such that the laser beam includes first wave fronts which are at least partially spherical

Methodology Applied

Scientific EffectOptical shaping:

Implementation Method 3

the metal is burned and vaporized after being heated up to ignition temperature by the laser beam

Methodology Applied

Scientific EffectLaser heating: Laser

Implementation Method 4

the reaction between the oxygen and the metal actually creates additional energy in the form of heat

Methodology Applied

Scientific EffectCombustion: Combustion

Implementation Method 5

The molten liquid metal, which has very low viscosity, is removed from the cut by the shear force of the oxygen jet

Methodology Applied

Scientific EffectShear force: Shear Stress

Implementation Method 6

the material is molten solely by the laser power and blown out of the cut kerf by the kinetic energy of the gas jet

Methodology Applied

Scientific EffectKinetic energy:

Data Source

PatentUS11554446B2Beam shaper and use thereof, device for laser beam treatment of a workpiece and use thereof, method for laser beam treatment of a workpiece

Publication Date: 2023.01.17 BYSTRONIC LASER AG

AI summary

A beam shaper (1) for shaping a laser beam is provided, including a first beam shaping section (2) designed for shaping a central part of the laser beam, and a second beam shaping section (3) designed for shaping a peripheral part of the laser beam. Moreover, a device for laser beam treatment of a workpiece and a method for laser beam treatment of a workpiece are provided.