Thermal Radiation Absorption in 3D Printing Irradiation Units
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Solution Overview
Problem
In powder bed fusion processes, temperature-induced changes in optical elements of the irradiation unit cause shifts in the focus position of the radiation beam, leading to reduced quality of three-dimensional work pieces.
Innovation Solution
An apparatus with an absorption device and a reflexion device is used to absorb and reflect radiation, respectively, within the process chamber and irradiation unit, minimizing temperature-induced changes in optical elements and preventing focus position shifts. The absorption device has a low hemispherical reflectance for thermal radiation, while the reflexion device has high hemispherical reflectance for thermal and electromagnetic radiation, effectively managing radiation to maintain beam stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If radiation energy is introduced into the raw material powder to melt and sinter it, then the three-dimensional work piece is produced, but thermal radiation causes temperature increase within the process chamber and irradiation unit, leading to temperature-induced changes in optical properties of optical elements and shift in focus position
Solution Approach 1:
The patent extracts and removes thermal radiation from the irradiation unit by introducing an absorption device that selectively absorbs thermal radiation wavelengths. This separates the useful electromagnetic radiation (for melting/sintering) from the harmful thermal radiation (causing temperature increase), allowing the latter to be absorbed and dissipated without affecting optical element temperatures.
Solution Approach 2:
The absorption device acts as an intermediary between the thermal radiation and the optical elements. It intercepts thermal radiation before it can reach and heat the optical elements, converting the thermal energy into a form that can be safely dissipated. This mediator protects the optical system from thermal effects while allowing the process to continue.
2Reliability
If the temperature of optical elements changes due to thermal radiation, then energy is transferred to the optical elements, but this causes temperature dependent change of optical properties and shifts focus position of the radiation beam
Solution Approach 1:
The patent converts the harmful thermal radiation into a beneficial protective mechanism. The absorption device is designed to preferentially absorb thermal radiation wavelengths while being transparent to the useful electromagnetic radiation wavelengths. This transforms what would be harmful heat energy into a protective function that shields the optical elements from thermal damage.
3Manufacturing precision
If an absorption device is introduced to absorb thermal radiation, then temperature-induced changes in optical elements are reduced, but the device complexity of the irradiation unit increases
Solution Approach 1:
The absorption device is not a complete enclosure but rather strategically positioned components within the irradiation unit. It applies the local quality principle by providing thermal radiation absorption only in the specific locations where thermal radiation would otherwise reach optical elements, rather than requiring a complete thermal management system throughout the entire unit.
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 ensures the production of high-quality three-dimensional work pieces by maintaining the focus position and spot position of the radiation beam, reducing thermal distortions and improving the overall precision and quality of the work pieces.
Implementation Method 1
An absorption device which is adapted to absorb radiation is provided in the process chamber and/or in the irradiation unit at such a position that it is capable of absorbing radiation occurring in an interior of the process chamber and/or in an interior of the irraditation unit
Implementation Method 2
a reflexion device which is adapted to reflect radiation, respectively, within the process chamber and irradiation unit, minimizing temperature-induced changes in optical elements
Implementation Method 3
The laser radiation penetrating into the powder layer causes heating and consequently melting or sintering of the raw material powder particles
Implementation Method 4
a raw material powder layer is applied onto a carrier and subjected to laser radiation in a site selective manner
Implementation Method 5
the refractive index of an optical fiber, a lens or another optical element or the geometry, in particular a curvature or a radius of a lens may change in dependence on the temperature prevailing within the process chamber
Data Source
AI summary
An apparatus (10) for producing a three-dimensional work piece (46) by irradiating layers of a raw material powder with electromagnetic or particle radiation comprises a process chamber (16) accommodating a carrier (12) and a powder application device (14) for applying a layer of raw material powder onto the carrier (12). The apparatus (10) further comprises an irradiation unit (26) for selectively irradiating the layer of raw material powder with electromagnetic or particle radiation in accordance with a geometry of a corresponding layer of the work piece (18) to be produced. An absorption device (50) which is adapted to absorb heat radiation emitted upon selectively irradiating the layer of raw material powder with electromagnetic or particle radiation is provided in the process chamber (16) and/or in the irradiation unit (26) at such a position that it is capable of absorbing radiation occurring in an interior of the process chamber (16) and/or in an interior of the irraditation unit (26).