Laser Cutting Gap Feedback for Focus Shift Compensation
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Solution Overview
Problem
Existing laser machining methods face challenges in maintaining focus stability due to focus shifts caused by heating of optical elements, leading to reduced cut quality and requiring complex, time-consuming calibration and measurement processes.
Innovation Solution
A method and apparatus that monitor and regulate geometric parameters of the cutting gap independently of the laser beam's caustic, allowing for real-time adjustment of the focus position and beam parameters such as width, diameter, and intensity distribution to maintain optimal cutting conditions without the need for calibration, by using detectors and adjustable optical elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If focus position is measured in the cutting head to counteract focus shift, then focus stability is improved, but the cutting head becomes expensive, heavy, and complicated
Solution Approach 1:
The focus measurement function is extracted from the cutting head and relocated to the workpiece surface. By measuring the cutting gap geometry directly at the workpiece, the cutting head is simplified while maintaining focus stability through continuous monitoring and adjustment of the focus position based on cutting gap feedback
Solution Approach 2:
The cutting gap serves as an intermediary indicator that reflects focus position. Instead of directly measuring focus position in the cutting head, the system uses the cutting gap geometry as a mediator to indirectly determine and control focus stability, simplifying the cutting head while maintaining reliability
2Measurement precision
If caustic measurement is performed to determine focus position, then focus position can be determined, but calibration steps are necessary and the process becomes complex
Solution Approach 1:
The system uses the cutting gap itself, which is already present during laser machining, as the measurement object. The cutting gap geometry automatically provides focus position information without requiring separate calibration steps or additional measurement infrastructure, making the process self-sufficient and eliminating complex calibration procedures
Solution Approach 2:
The system transitions from measuring physical caustic parameters that require calibration to monitoring cutting gap geometric parameters that directly reflect focus position. By changing the measurement parameter from caustic dimensions to cutting gap dimensions, the system eliminates calibration requirements while maintaining measurement precision
3Reliability
If focus position is repeatedly determined during machining, then focus stability is maintained, but the process becomes time-consuming
Solution Approach 1:
The cutting gap monitoring is performed continuously during the laser machining process itself, without interrupting the useful action of material removal. The same laser beam that machines the workpiece also creates the cutting gap that serves as the measurement reference, allowing simultaneous machining and focus monitoring to maintain stability without reducing productivity
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 enables simple, efficient, and flexible regulation of cutting gap parameters, maintaining consistent cut quality without the need for complex focus position determination, thus addressing the issue of focus shifts and improving the stability of the laser machining process.
Implementation Method 1
the metallic material of the workpiece is burned, for example, after it has been heated to the ignition temperature by the laser beam
Implementation Method 2
The reaction between oxygen and the material of the workpiece generates additional heat that supports the cutting process
Implementation Method 3
the material of the workpiece is only melted by the laser power and can be blown out of the cutting gap by the kinetic energy of the gas stream
Implementation Method 4
The focus of the machining laser beam can experience a focus shift (shifting of the focus) over time and with increasing power, in particular due to the heating of optical elements that are used for optical imaging of the laser beam
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
A method of laser machining a workpiece is provided, with a) generation of a machining laser beam and imaging of the machining laser beam on the workpiece with at least one optical element; b) machining of the workpiece with the imaged machining laser beam and generation of a cutting gap in the workpiece; c) monitoring of at least one geometric parameter of the cutting gap during step b); and d) regulating the monitored geometric parameter of the cutting gap during step c) for harmonisation with a target value of the geometric parameter of the cutting gap. Further provided is an apparatus for laser machining a workpiece.