Optical Sensing for Additive Manufacturing Thermal Monitoring
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Solution Overview
Problem
Current additive manufacturing processes lack non-destructive methods for verifying the mechanical, geometrical, and metallurgical properties of production parts, as conventional quality assurance testing often requires destructive testing, which is not applicable to production parts.
Innovation Solution
The implementation of optical sensing techniques to track in-process physical phenomena, specifically using thermal energy density (TED) metrics, to monitor and adjust energy application during additive manufacturing, allowing for real-time quality inference and process control by comparing sensor readings to baseline datasets and adjusting energy source outputs accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional quality assurance testing is used to verify part properties, then accurate quality verification is achieved, but the part is destroyed
Solution Approach 1:
The patent replaces mechanical/physical destructive testing methods with optical sensing techniques. Optical sensors detect thermal radiation emitted by the melt pool during additive manufacturing, enabling non-contact measurement of temperature and process quality without physically contacting or damaging the part. This substitution of mechanical testing with optical detection resolves the contradiction between accurate quality verification and part destruction.
Solution Approach 2:
The patent introduces thermal radiation as an intermediary medium for quality assessment. Instead of directly testing the part's mechanical properties (which would destroy it), the system detects thermal radiation emitted by the melt pool as an intermediate indicator of process quality. This intermediary measurement allows inference of part quality without direct contact or destruction of the final product.
2Reliability
If optical sensing techniques are implemented for real-time monitoring, then non-destructive quality verification is achieved, but device complexity increases
Solution Approach 1:
The patent makes the optical sensing system serve multiple functions: it simultaneously monitors melt pool temperature, tracks process quality, and provides data for real-time control adjustments. By making the optical sensing apparatus multi-functional, the patent reduces the need for separate testing equipment, thereby mitigating the increase in device complexity while maintaining non-destructive quality verification capability.
Solution Approach 2:
The system uses the thermal radiation naturally emitted by the melt pool during additive manufacturing as the measurement signal. The process itself provides the measurement information without requiring external illumination or additional active sensing elements, reducing system complexity. The melt pool essentially 'self-illuminates' through thermal radiation, allowing the sensors to passively detect process quality.
3Manufacturing precision
If melt pool temperature variations are reduced for better quality, then manufacturing precision is improved, but process control difficulty increases
Solution Approach 1:
The patent implements a closed-loop feedback control system where optical sensors continuously measure melt pool temperature, the measured values are compared against target values, and control signals are automatically generated to adjust energy source parameters. This automated feedback mechanism reduces manual process control difficulty while maintaining high manufacturing precision through real-time temperature regulation of the melt pool.
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 non-destructive quality verification and process control, reducing discontinuities in the melt pool size and temperature variations, thereby improving the accuracy and consistency of additive manufacturing processes, and preventing defects in production parts.
Implementation Method 1
measuring an amount of energy radiated from the build plane at the first wavelength; measuring an amount of energy radiated from the build plane at the second wavelength; determining variations in temperature of an area of the build plane traversed by the plurality of scans based upon a ratio of energy radiated at the first wavelength to energy radiated at the second wavelength
Data Source
AI summary
This disclosure describes various methods and apparatus for characterizing an additive manufacturing process. A method for characterizing the additive manufacturing process can include generating scans of an energy source across a build plane; measuring an amount of energy radiated from the build plane during each of the scans using an optical sensing system that monitors two discrete wavelengths associated with a blackbody radiation curve of the layer of powder; determining temperature variations for an area of the build plane traversed by the scans based upon a ratio of sensor readings taken at the two discrete wavelengths; determining that the temperature variations are outside a threshold range of values; and thereafter, adjusting subsequent scans of the energy source across or proximate the area of the build plane.