Laser Speckle Photometry for Real-Time Melt Pool Defect Detection
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Solution Overview
Problem
Current monitoring methods for laser machining processes in powder bed-based additive manufacturing lack real-time, high-resolution capabilities to detect defects and anomalies, leading to potential material waste and increased costs due to inadequate process control.
Innovation Solution
A method utilizing high-resolution, time-resolved laser speckle photometry with a high-speed camera to record and evaluate the reflected and scattered radiation from the machining process, allowing for inline monitoring of surface topography, melt pool size, and porosity, enabling real-time process control and defect detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional monitoring methods are used, then device complexity is reduced, but measurement precision and real-time detection capability deteriorate
Solution Approach 1:
The patent introduces a beam splitter as an intermediary optical element that directs different wavelengths of light to different detectors. The beam splitter separates the processing laser wavelength (for melt pool monitoring) from other wavelengths (for surface topology monitoring), enabling multi-parameter measurement without requiring direct line-of-sight access to the melt pool and without significantly increasing system complexity.
Solution Approach 2:
The monitoring device is designed to perform multiple functions simultaneously: it monitors melt pool characteristics, detects surface topology changes, identifies defects, and provides real-time process control. By integrating multiple detection capabilities into a single system, the patent achieves high measurement precision across multiple parameters without proportionally increasing device complexity.
2Manufacturing precision
If high-resolution real-time monitoring is implemented, then manufacturing precision is improved, but loss of time for data processing increases
Solution Approach 1:
The patent implements preliminary action by continuously capturing and pre-processing monitoring data during the laser processing operation. The system maintains a continuous stream of high-resolution images and spectral data, pre-evaluating them to detect defects and process anomalies before they compromise component quality. This allows real-time process control without significant time loss, as the data evaluation occurs concurrently with manufacturing.
3Reliability
If comprehensive process monitoring is applied, then reliability of component quality is improved, but device complexity increases
Solution Approach 1:
The beam splitter serves as a key intermediary that enables comprehensive monitoring without requiring multiple complex access paths to the melt pool. By optically separating different wavelength ranges and directing them to appropriate detectors, the system achieves reliable multi-parameter monitoring (melt pool temperature, surface topology, defects) through a relatively simple optical architecture.
Solution Approach 2:
The system creates optical copies of the melt pool and surface information at different wavelengths and detection planes. By capturing reflected and emitted radiation at multiple wavelengths simultaneously, the system generates multiple informational copies of the same physical region, enabling comprehensive quality assurance through redundant measurement channels that cross-validate each other.
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
Enables real-time, high-resolution monitoring and control of the laser machining process, reducing material waste and costs by detecting defects and anomalies promptly, and improving the quality of components produced.
Implementation Method 1
spatially and temporally resolved images suitable for speckle photometry are recorded from the radiation reflected and/or scattered from the surface
Implementation Method 2
spatially and temporally resolved images suitable for speckle photometry are recorded from the radiation reflected and/or scattered from the surface
Implementation Method 3
A method utilizing high-resolution, time-resolved laser speckle photometry
Implementation Method 4
laser speckle photometry with a high-speed camera to record and evaluate the reflected and scattered radiation
Data Source
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AI summary
The invention relates to a method and a device for monitoring a laser processing process in which at least one processing laser beam is guided along one or more paths over a surface to be processed in order to locally melt the surface. In the method, radiation from the processing laser beam or an illumination laser (7) reflected and/or scattered by the surface during the processing process is captured with spatial and temporal resolution using a high-speed camera (2), and at least the topography or roughness of the surface in one or more sections of interest, the size of the respective melt pool (14), and the porosity at or below the surface in the respective sections of interest are automatically determined from the images using static and time-resolved speckle photometry.This allows state variables of the machined surface to be determined with high spatial resolution in real time, which can also be used to control the machining process.