In Situ Melt Pool Pyrometry for LPBF Defect Detection
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Solution Overview
Problem
Current quality control methods for Laser Powder Bed Fusion (LPBF) parts, especially for complex geometries like microlattices, struggle to effectively detect single-strut defects due to limited spatial resolution and inability to identify missing or broken struts in real-time, hindering widespread adoption and certification of additively manufactured parts.
Innovation Solution
A system utilizing a pyrometer and dichroic mirror to collect and analyze thermal emission signals from the melt pool in real-time, allowing for in situ detection of anomalies and defects in microlattices by distinguishing between normal and defective struts based on pyrometry signal intensity, which can be integrated with existing LPBF machines without modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional non-destructive inspection techniques (X-ray computed tomography, acoustic emission monitoring, ultrasonic inspection) are used, then part quality can be evaluated, but the complex part geometry makes quality control difficult and these methods cannot effectively detect single-strut defects in microlattices
Solution Approach 1:
The system performs inspection during the manufacturing process itself (in-situ monitoring), detecting defects as they form rather than after completion. The pyrometer monitors melt pool characteristics in real-time, enabling early detection of missing or broken struts before the part is finished, thus avoiding the need for difficult post-fabrication inspection of complex geometries.
Solution Approach 2:
The patent replaces traditional mechanical/optical inspection methods (X-ray, ultrasonic, acoustic emission) with thermal radiation detection using a pyrometer. By measuring the thermal emission from the melt pool, the system achieves precise defect detection without the complexity and limitations of other non-destructive testing methods.
2Measurement precision
If optical imaging with whole-layer camera images is used to identify powder spreading defects, then gross defects can be identified, but the limited spatial resolution makes it challenging to identify single-strut defects in microlattices
Solution Approach 1:
Instead of imaging the entire layer with limited resolution, the pyrometer focuses on locally measuring the thermal emission from the specific melt pool region where material is being deposited. This localized measurement approach provides high spatial resolution for detecting small defects like single-strut issues without requiring whole-layer imaging capability.
3Reliability
If high-speed pyrometer aligned coaxially to the build laser is used, then melt pool thermal emission can be monitored, but the data analysis does not include routes for identifying component defects such as missing struts in microlattices
Solution Approach 1:
The system implements a feedback loop where pyrometer data is continuously collected and analyzed in real-time. The controller compares measured thermal emission characteristics against expected values and provides feedback to identify when defects occur, enabling actionable quality control decisions during manufacturing rather than just data collection.
Solution Approach 2:
The patent analyzes changes in pyrometer signal parameters (intensity, temporal characteristics) that correspond to different defect conditions. By monitoring parameter variations in the thermal emission data, the system can distinguish between normal process variations and actual defects such as missing or broken struts.
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, in situ identification of defective struts during the manufacturing process, improving the ability to ensure part quality and certification by distinguishing between normal and defective struts with high accuracy, even for small features like microlattice struts, and can be universally applied across different LPBF platforms.
Implementation Method 1
An optical sensor may be included which is configured to receive a signal reflected from the melt pool. The reflected signal is indicative of a thermal emission of the feedstock material
Implementation Method 2
A dichroic mirror may be configured to pass the laser beam through without modification, and to redirect the reflected pyrometry signal from a path coaxial with the laser beam to a path non-parallel to the laser beam
Implementation Method 3
an energy source configured to generate a beam of energy for creating a melt pool in a layer of feedstock material being selectively fused
Data Source
AI summary
A system and method is disclosed for detecting anomalies in an additively manufactured part. An energy source generates a signal forming an optical beam for creating a melt pool in a layer of feedstock material being selectively fused to make a part in an additive manufacturing operation. A sensor is configured to receive a signal reflected from the melt pool. The reflected signal forms a thermal signal indicative of a temperature of the feedstock material at a known location on a layer of the feedstock material while the feedstock material is being fused at the known location. A controller receives and analyzes data relating to the received signal to determine if an anomaly exists at the known location.