Sintering monitoring method
Inventors
Nussbaum, Justin • Crane, Nathan Brad
Assignees
University of South Florida • University of South Florida St Petersburg
Publication Number
US-11376795-B1
Publication Date
2022-07-05
Expiration Date
2039-07-22
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Abstract
The disclosed subject matter relates to methods for monitoring or controlling a manufacturing process of a material by determining when a variation in surface characteristics takes place. Such surface characteristics correlates to the processing condition of the material and can include density, roughness, porosity, or planarity on a surface of the material. The methods can include herein can include directing a solvent or energy on a surface of the material to form an at least partially modified surface, directing light at an incident angle with respect to the at least partially modified surface, measuring one or more predetermined properties of light reflected from the at least partially modified surface, determining that the material is fully processed based on the measured predetermined property of the light reflected, and optionally adjusting a processing parameter of the manufacturing process in response to the measured predetermined property.
Core Innovation
The invention provides methods for monitoring or controlling a manufacturing process of a material by determining when a variation in surface characteristics occurs, where these characteristics correlate to the processing condition of the material, such as density, roughness, porosity, or planarity. The methods include directing a solvent or energy onto a material surface to form a partially modified surface, directing light at a given incident angle onto this surface, measuring predetermined properties of the light reflected from the surface, and determining if the material is fully processed based on the measured property value. Optionally, the process allows for adjusting a processing parameter in response to the measured property.
The problem addressed by the invention is that existing surface monitoring technologies for powder bed fusion additive manufacturing mostly rely on emitted light to track temperature, without providing information on important material properties such as phase, surface roughness, or porosity. Furthermore, infrared systems for sub-Draper point temperatures are costly and lack spatial resolution compared to visible light alternatives. The industry lacks an effective in-situ, area-based feedback method for monitoring and controlling such processes, particularly for large-area exposures.
The methods disclosed in the patent can be applied to additive manufacturing processes such as melting, sintering, densification, or surface smoothing, and are applicable to materials including powders, fibers, and composites, often polymers. By measuring properties such as the number of reflective spots, spacing, and intensity of reflected light, and comparing them to predetermined control limits or calibration data, the process enables quantitative monitoring and real-time feedback-based control. These methods can detect process variations, surface defects, or completion based on the reflection characteristic transitions, thereby enabling closed-loop adjustment of process parameters during manufacturing.
Claims Coverage
The patent contains three independent claims, each presenting a distinctive inventive feature directed to methods for monitoring or controlling additive manufacturing or surface treatment processes.
Monitoring or controlling additive manufacturing process using transition of diffusive to specular reflection
A method comprising: - Directing a solvent or energy on a surface of a powder material (polymer, fibrous, or fabricated composite) to form a partially modified surface. - Directing light at an incident angle to the modified surface. - Measuring predetermined properties of reflected light (amount of reflective spots, spacing, or intensity), where the step measures a transition from diffusive to specular reflection. - Determining that the material is fully processed when the measured property reaches a target value (about zero when the incident angle is not normal and different from the detector angle). - If the target value is not reached, adjusting a processing parameter of the manufacturing process in response.
Monitoring or controlling melting or sintering process by transition in reflection properties
A method comprising: - Projecting energy on a polymer powder material surface to partially sinter or melt it. - Directing light at an incident angle to the partially processed surface. - Measuring predetermined properties of reflected light that correlate with the processing condition, with the measurement capturing the transition from diffusive to specular reflection. - Determining full sintering or melting when the measured property reaches a target value (about zero for a specific geometric configuration). - Adjusting a processing parameter if the property does not reach the target value.
Monitoring or controlling surface treatment for smoothing or defect reduction using reflected light measurement
A method comprising: - Directing a solvent or energy on an exterior material surface to reduce/eliminate defects and smooth the surface. - Directing light at an incident angle on the surface. - Measuring predetermined properties of the reflected light corresponding to the material's planarity, with a measured transition from diffusive to specular reflection. - Determining planarity when the measured property reaches a target value (about zero in specified geometric conditions). - Adjusting a processing parameter of the surface treatment if the value has not been reached.
In summary, the inventive features focus on real-time monitoring and control of manufacturing or treatment processes by detecting transitions in surface reflection characteristics, and adjusting process parameters based on quantitative, in-situ reflected light measurements.
Stated Advantages
Provides a lower cost, higher speed, and higher spatial resolution method for monitoring changes in material surface characteristics compared to temperature-based infrared systems.
Enables in-situ, simultaneous area-based feedback control during manufacturing, allowing for quantitative, real-time assessment and adjustment of process conditions.
Allows monitoring of material properties such as phase, density, roughness, or porosity, which are not accessible by conventional temperature monitoring.
Facilitates improved process quality by enabling correction of process abnormalities before defects occur or before a full manufacturing cycle is run.
Documented Applications
Monitoring or controlling additive manufacturing processes such as powder bed fusion for metals, ceramics, polymers, and composites.
Monitoring and controlling surface treatment processes, including densification, fusion, smoothing, or melting of materials by heat or solvent exposure.
In-situ monitoring of powder bed fusion additive manufacturing, including large area projection sintering (LAPS) and related technologies.
Quality assurance during manufacturing by real-time monitoring of surface characteristics and generation of feedback or alerts for process parameter adjustment.
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