Laser Reactive Cutting of Thick Steel With Elevated Focus
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Solution Overview
Problem
Existing laser cutting methods for thick metal workpieces face limitations in cutting speed and quality, particularly when using reactive cutting with oxygen-containing gases.
Innovation Solution
The method involves positioning the laser beam focal point between 10 mm and 30 mm above the workpiece surface, using a high-power laser (at least 5 kW) with a nozzle close to the workpiece, and an oxygen-containing cutting gas to enhance cutting efficiency and quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the focal position is at or below the workpiece surface for thick workpieces, then the cutting process can penetrate the material, but the cutting speed is limited and the quality of the cut deteriorates
Solution Approach 1:
The patent shifts the focal position from the traditional plane (at or below the workpiece surface) to a new spatial dimension (above the workpiece surface by 10-30mm). This dimensional change allows the laser beam to preheat and react the metal surface before contact, enabling faster cutting speeds while maintaining or improving cut quality through controlled exothermic reactions.
2Productivity
If reactive cutting with oxygen-containing gas is used for thick workpieces, then cutting efficiency improves, but substantial burr formation and material quality compromise occur
Solution Approach 1:
The patent applies preliminary action by positioning the focal point above the workpiece surface, allowing the laser beam to preheat and initiate exothermic reactions in the metal surface before the cutting gas contacts the material. This pre-conditioning of the metal surface enables cleaner cuts with reduced burr formation while maintaining cutting efficiency.
3Productivity
If high laser power is used to cut thick workpieces, then cutting speed increases, but the heat input to the workpiece increases
Solution Approach 1:
The patent introduces an intermediary mechanism by utilizing exothermic chemical reactions between the oxygen-containing cutting gas and the metal surface. These reactions generate additional heat at the cut front, supplementing the laser energy and enabling faster cutting speeds while reducing the overall heat input required from the laser source.
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 significantly increases cutting speed and improves cut quality for thick metal workpieces, especially those made of inferior material, while reducing the overall heat input.
Implementation Method 1
a laser beam whose focal position is located in the workpiece in a depth that is greater than half of the thickness of the workpiece
Implementation Method 2
If this gas ('assist gas', 'cutting gas') contains a substantial portion of oxygen, and a chemical reaction ('burning') takes place at the position of incidence, the laser cutting is also called 'reactive cutting' or 'flame cutting'
Implementation Method 3
a directed laser beam moves relative to the metal workpiece to locally create a cut in the metal material at the position of incidence of the laser beam on the workpiece
Data Source
Figure 1~2
AI summary
A laser cutting method of relatively thick workpieces (208), especially of steel, with an oxygen containing cutting gas is more efficient compared to the prior art if the focal position is substantially above the workpiece (208), e.g. at least 1 mm above the workpiece (208), for example at least 5 mm, at least 8 mm or at least 10 mm above the workpiece. An especially efficient process results if additionally the nozzle (121) from which the cutting gas is emitted is close to the workpiece (208), e.g. at a distance of at most 1 mm.