Normalized Thermal Scan Monitoring for Additive Defect Detection
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Solution Overview
Problem
Conventional quality assurance methods for additive manufacturing are limited, particularly in non-destructively verifying the integrity of parts produced by processes like selective laser sintering, where data from wide-area thermal sensors can be biased by varying distances and scan lengths, making it difficult to accurately characterize the weld pool's size and temperature variations.
Innovation Solution
The method involves using an optical temperature sensor to monitor the heat source's scans across a powder bed, generating characteristic curves from recorded intensity and duration data, and comparing these to baseline curves to detect defects by determining differences that exceed a predetermined threshold, while accounting for distance and scan length variations using additional sensors and data normalization techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a wide area thermal sensor is used to monitor the additive manufacturing process, then the coverage area is increased, but the measurement precision deteriorates due to varying distances between the sensor and different portions of the build plane
Solution Approach 1:
The patent divides the build plane into multiple discrete regions, each with its own characteristic curve. By segmenting the monitoring area into smaller zones, the sensor can maintain adequate measurement precision within each region while still providing broad coverage across the entire build plane. The varying distance effects are localized to each region rather than affecting the entire area uniformly.
Solution Approach 2:
The patent transforms the raw sensor data by generating characteristic curves that normalize temperature readings across different regions. This parameter transformation compensates for the distance variations, allowing the wide-area sensor to maintain measurement precision despite the varying distances to different portions of the build plane.
2Adaptability or versatility
If the heat source scans across the powder bed to create complex three dimensional structures, then the manufacturing versatility is improved, but the manufacturing precision deteriorates due to variations in weld pool size and temperature
Solution Approach 1:
The patent implements a feedback mechanism where characteristic curves are generated from sensor data and compared against baseline curves to detect deviations. This feedback loop allows real-time monitoring and detection of weld pool variations, enabling corrective actions to maintain manufacturing precision even when scanning complex geometries that inherently cause variations in weld pool size and temperature.
Solution Approach 2:
The patent establishes baseline characteristic curves before production scanning begins. These pre-established references allow for comparison during the manufacturing process, enabling detection of deviations from expected weld pool behavior before they result in defective parts. This preliminary characterization helps maintain precision across varied scan patterns.
3Measurement precision
If conventional destructive testing is used to verify part quality, then the measurement precision is improved, but the productivity deteriorates due to part destruction and inability to apply to production parts
Solution Approach 1:
The patent replaces mechanical destructive testing with optical sensing and data analysis. By using a wide area thermal sensor to monitor the additive manufacturing process and analyze characteristic curves, the system provides quality verification without physically destroying the part. This substitution enables non-destructive testing that maintains productivity while providing sufficient quality assurance for production parts.
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 allows for non-destructive, accurate identification and characterization of defects in additive manufacturing processes, ensuring the quality of produced parts by correcting for geometric errors and variations in scan patterns, thereby enhancing the reliability of quality control.
Implementation Method 1
monitoring a heat source scanning across a powder bed using an optical temperature sensor
Implementation Method 2
the heat source melts the incrementally added powder by welding regions of the powder layer creating a moving molten region
Implementation Method 3
the heat source melts the incrementally added powder by welding regions of the powder layer
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
The disclosed embodiments relate to the monitoring and control of additive manufacturing. In particular, a method is shown for removing errors inherent in thermal measurement equipment so that the presence of errors in a product build operation can be identified and acted upon with greater precision. Instead of monitoring a grid of discrete locations on the build plane with a temperature sensor, the intensity, duration and in some cases position of each scan is recorded in order to characterize one or more build operations.