IR Radiation Sensing for Electron Beam Additive Manufacturing
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Solution Overview
Problem
In electron beam powder bed fusion (EB-PBF) systems, accurately measuring temperature and other parameters of the powder bed surface during a print cycle is challenging due to the chaotic environment in the vacuum chamber, leading to potential overheating and damage to the build piece, as loose powder vaporization and condensation on temperature sensors compromise measurement integrity.
Innovation Solution
An infrared (IR) radiation sensing system is integrated, comprising a radiation collector, sensor, and occlusion member, which receives IR radiation from the powder bed, determines surface information, and dynamically adjusts electron beam intensity and scanning rate in real-time to maintain optimal printing conditions, using a feedback loop to prevent overheating or underheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature sensors are used to measure powder bed surface temperature, then temperature measurement is possible, but measurement accuracy deteriorates due to powder vaporization and condensation on sensors
Solution Approach 1:
The patent introduces an infrared radiation collector as an intermediary device that indirectly measures powder bed surface temperature by collecting IR radiation from the surface. This mediator allows temperature measurement without direct contact between sensors and the powder bed, avoiding the harmful effects of powder vaporization and condensation that plague direct temperature sensors.
Solution Approach 2:
The patent replaces the mechanical/contact-based temperature sensing system with an optical/infrared-based measurement system. By substituting physical contact sensors with non-contact IR radiation collection, the system eliminates the reliability issues caused by powder contamination while maintaining temperature measurement capability.
2Measurement precision
If the radiation collector is exposed during the print cycle, then IR radiation measurement is possible, but the radiation collector is damaged by powder vaporization and condensation
Solution Approach 1:
The patent implements a dynamic occlusion member that can move between exposed and retracted positions. During re-coat cycles, the occlusion member is retracted to allow IR measurement. During print cycles, the occlusion member extends to protect the radiation collector from powder vaporization. This dynamic positioning resolves the contradiction between needing exposure for measurement and protection for reliability.
Solution Approach 2:
The system employs periodic switching between measurement mode (occlusion member retracted during re-coat cycles) and protection mode (occlusion member extended during print cycles). This periodic action allows the radiation collector to be exposed only when necessary for measurement while protected during harmful print operations.
3Reliability
If real-time temperature measurement is implemented, then overheating can be prevented, but system complexity increases due to additional sensing and control components
Solution Approach 1:
The infrared radiation collector serves multiple functions: it measures powder bed surface temperature, monitors melt pool conditions, and provides data for real-time process control. By making this single component multi-functional, the system achieves comprehensive monitoring capability without proportionally increasing overall system complexity.
Solution Approach 2:
The patent implements a feedback control loop where IR radiation measurement data is continuously fed back to adjust electron beam parameters in real-time. This feedback mechanism enables automatic temperature control and overheating prevention, with the control system intelligently adjusting beam intensity and scan speed based on measured conditions, thereby improving reliability through automation rather than manual intervention.
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 solution enables precise control of printer parameters, enhancing the quality and integrity of the build piece by accurately measuring temperature and other surface characteristics in real-time, reducing the risk of overheating and improving print quality.
Implementation Method 1
a radiation collector that receives infrared (IR) radiation from a powder bed surface
Implementation Method 2
an electron beam source that selectively fuses layers of powder on a powder bed
Implementation Method 3
the electron beam is applied to melt areas of the powder layer that coincide with the cross-section of the build piece in the layer
Data Source
AI summary
Apparatuses for dynamically sensing infrared (IR) radiation in an electron beam powder bed fusion (EB-PBF) printer are provided. A radiation collector receives radiation from a surface of the powder bed. An IR-transparent material rejects one or more non-IR wavelengths, and a lens focuses the IR radiation onto an optical fiber. The IR radiation is carried from the vacuum chamber of the printer to a sensor, where IR information is determined based on the received IR radiation. The IR information may be received from the sensor and used by the print controller to modify one or more parameters, such as beam intensity or scanning rate, on the fly or during the next print cycle. An occlusion member can be used to selectively block or expose the radiation collector to protect the radiation collector from condensation of vapor from vaporization of particles at high temperatures.