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 caustic, by adjusting the focus position and beam parameters such as width, diameter, and intensity distribution of the machining laser beam, allowing for real-time correction without the need for focus position determination or calibration.
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:
Instead of measuring focus position directly in the cutting head, the patent uses a camera to capture images of the cutting gap, creating a visual copy that represents the focus state. This indirect measurement approach avoids adding complex measurement devices to the cutting head while still enabling focus stability monitoring through image analysis of the cutting gap characteristics
2Reliability
If indirect measurement methods are used to compensate for focus shift, then focus stability can be maintained, but the process becomes complicated and time-consuming
Solution Approach 1:
The patent implements a feedback mechanism where the camera continuously monitors the cutting gap during laser machining, and the system automatically adjusts focus position based on real-time image analysis. This closed-loop feedback enables rapid focus compensation without time-consuming manual calibration or complex computational derivatives, as the system self-corrects based on direct visual feedback from the cutting zone
Solution Approach 2:
The patent replaces complex mechanical measurement systems (such as thermal variable sensors and computational derivative calculations) with an optical imaging system using a camera. This substitution simplifies the measurement process by using light-based optical fields to directly visualize and measure cutting gap characteristics, eliminating the need for complex mechanical or thermal sensing apparatus
3Measurement precision
If focus position is determined by camera-based cutting gap measurement, then focus position can be monitored, but calibration steps and repeated measurements are necessary making the process complex
Solution Approach 1:
The system uses the inherent illumination (process light) generated during laser cutting itself to illuminate the cutting gap for camera measurement. This self-service approach eliminates the need for separate calibration steps and external illumination sources, as the cutting process provides its own measurement lighting. The system automatically adapts to different cutting conditions without requiring manual recalibration
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 focus stability and improving cut quality without the complexity of traditional methods, allowing for continuous and repeated adjustments during laser cutting processes.
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
When cutting with an inert gas such as nitrogen or argon, the material of the workpiece is only melted by the laser power
Implementation Method 4
imaging the machining laser beam on the workpiece with at least one optical element
Implementation Method 5
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
Data Source
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.