Thermionic Emission Monitoring for LPBF Temperature Control
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Solution Overview
Problem
Existing additive manufacturing (AM) systems face challenges in non-destructive defect detection and laser beam focusing/co-alignment, which affect build quality and consistency, particularly in performance-critical applications.
Innovation Solution
An electronic controller system with a current measuring subsystem to monitor thermionic emission during laser scanning, enabling in-situ temperature control and calibration of laser power to maintain desired temperatures, and a method for focusing and co-aligning multiple lasers for consistent build conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical diagnostics are used to detect defects during LPBF, then defect detection capability is improved, but device complexity and integration difficulty increase
Solution Approach 1:
The patent combines multiple diagnostic functions (optical imaging, photodiode measurements, spectroscopy) into a single integrated monitoring system that operates coaxially with the process laser. This merging of functions reduces the number of separate equipment platforms needed and simplifies integration into the LPBF machine while maintaining high defect detection capability
Solution Approach 2:
The monitoring system is designed to perform multiple functions simultaneously: detecting surface morphological anomalies, measuring melt pool characteristics, identifying spatter and vapor plume dynamics, and predicting process quality. This multi-functionality reduces the need for multiple separate diagnostic tools and their associated integration complexities
2Speed
If SD-OCT is used for high speed optical metrology, then sampling rate is improved, but capability to make operando measurements of melt pool region deteriorates
Solution Approach 1:
The patent segments the optical detection functions into different components: optical imaging for surface morphology, photodiodes for thermal emission and melt pool monitoring, and spectroscopy for vapor plume analysis. Each segment is optimized for its specific function and operates in conjunction with others, allowing high sampling rates while maintaining reliable operando measurements of the melt pool region
Solution Approach 2:
The patent uses the process laser itself as an intermediary to enable coaxial viewing of the melt pool region. By looking through the laser beam path, the system can directly observe melt pool characteristics during processing without requiring separate access paths, thus enabling reliable operando measurements while maintaining high sampling rates
3Measurement precision
If ex situ platforms are used for optical metrology, then measurement capability is improved, but integration into full-scale LPBF machine deteriorates
Solution Approach 1:
The patent merges the optical metrology functions directly into the LPBF machine structure by installing cameras, photodiodes, and spectrometers within the processing chamber and aligning them coaxially with the process laser. This integration eliminates the need for separate ex situ platforms and allows real-time monitoring during manufacturing
Solution Approach 2:
The monitoring system uses the existing process laser and chamber infrastructure to provide its own measurement capabilities. The process laser serves as both the manufacturing tool and the illumination source for optical imaging, while the chamber structure provides the mounting framework for sensors, making the system self-sufficient and easier to integrate
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
Provides in-process monitoring and optimization of laser power, ensuring consistent build quality by detecting temperature deviations and automating power adjustments, and facilitating rapid, cost-effective calibration of laser focus and alignment without requiring additional equipment.
Implementation Method 1
an optical light source to heat a powder bed material layer and to melt the powder bed
Implementation Method 2
The current measuring subsystem may be in electrical communication with at least one of a conductive substrate or a powder bed layer deposited on the conductive substrate... to detect a current flow as at least one of the conductive substrate or the powder bed layer is heated
Data Source
AI summary
The present disclosure relates to a system which may have an electronic controller, an optical light source controlled by the electronic controller which generates a beam having an output power level, and a current measuring subsystem (CMS) electrically coupled to a conductive substrate (e.g., metal substrate (MS)) while a powder bed layer (PBL) is deposited on the MS. The CMS may be in communication with the electronic controller and detects a current flow as at least one of the MS or the PBL is heated when the beam is scanned over the PBL. The CMS generates a current flow signal in accordance with the detected current flow. The current flow signal is used by the electronic controller to determine when the temperature of at least one of the substrate or the PBL is at least one of above or below a desired temperature.