Onset of Melting Detection via Multi-Pixel Thermal Differential
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Solution Overview
Problem
Existing methods for determining the onset of melting in three-dimensional object formation from particulate materials face challenges in accurately detecting the melting point, especially when using infrared heat sources, due to misalignment and excessive melting, which affects the quality of the objects being formed.
Innovation Solution
A method involving a temperature sensor with multiple pixels to monitor temperature differences between specific regions on a reference area, where a heat source creates a temperature differential between these regions, allowing for precise determination of the onset of melting by analyzing the evolution of temperature over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the rate of heating is reduced significantly to allow detection of the onset of melting, then the temperature increase is small enough for accurate detection, but the build bed surface alignment deviates due to piston movement and container wall distortions
Solution Approach 1:
A reference area is introduced as an intermediary element that is heated by the heat source while being monitored by the temperature sensor. This reference area serves as a mediator between the heat source and the build bed surface, allowing alignment calibration without requiring actual build bed surface measurements during the calibration process
Solution Approach 2:
The reference area acts as a copy or surrogate of the build bed surface for calibration purposes. By calibrating the temperature sensor against the reference area, the system obtains alignment data without directly measuring the build bed surface, thus avoiding alignment deviations caused by piston movement
2Object-affected harmful factors
If the build bed surface is lowered to increase distance from the heat source, then excessive melting is prevented, but misalignment between the temperature sensor and build bed surface occurs
Solution Approach 1:
The reference area serves as an intermediary target that receives heating from the heat source at the elevated position. The temperature sensor monitors this reference area to determine alignment, allowing the heat source to be positioned at the correct build distance without requiring the build bed surface to be in its final position during calibration
3Device complexity
If a single temperature curve is analyzed in isolation, then the measurement process is simple, but accurate determination of onset of melting is challenging due to gradual characteristic rate changes
Solution Approach 1:
The temperature monitoring is segmented into multiple discrete measurement points (first temperature location and second temperature location) within the reference area. By analyzing temperature differences between these segmented locations rather than a single curve, the system achieves more accurate detection of the onset of melting through comparative analysis
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 enables accurate detection of the onset of melting, preventing excessive material fusion and ensuring consistent quality in 3D object formation by providing precise temperature control and alignment.
Implementation Method 1
a temperature sensor, such as a pyrometer or thermal camera, that detects the temperature of the surface of the layer being processed
Implementation Method 2
a heat source is passed over the build bed to apply radiation to selectively fuse a cross section of the object
Implementation Method 3
accurate knowledge of the onset of melting (or fusion) since control over the process of fusion is material dependent
Data Source
Figure 1~2
Figure 3A~3B
Figure 3C~3E
AI summary
Provided is a method for determining the onset of melting of a material and comprising providing a layer of the material; defining a reference area within the layer of material; providing a temperature sensor and a heat source above the reference area, the temperature sensor comprising a plurality of pixels configured to monitor the temperature of the reference area; selecting a first pixel and a second pixel to form a first reference pair of pixels of the temperature sensor to detect the temperature of corresponding first and second regions within the reference area; operating the heat source to heat the reference area over a duration of time, while monitoring, using the reference pair of pixels, the temperature of the two regions, wherein the heat source causes a temperature difference between the two regions such that the first and second pixel detect respective different temperatures over the duration of time; and determining the onset of melting of the material from the evolution of the temperature difference over the duration of time. Further provided is a controller for carrying out the method and an apparatus for the layer by layer formation of a three-dimensional object from particulate material is also provided, comprising the temperature sensor, and in which the onset of melting as determined in situ may be applied as a set point for measurement of the temperature sensor.