Additive Manufacturing Getter for Atmosphere Control
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Solution Overview
Problem
Existing additive manufacturing techniques, such as selective laser melting (SLM) and selective laser sintering (SLS), face challenges in maintaining consistent low oxygen, nitrogen, and hydrogen levels in the build chamber atmosphere, leading to inconsistent part properties and hydrogen gas porosity due to material reactivity and gas absorption during the layer-by-layer solidification process.
Innovation Solution
Incorporating a gas recirculation circuit with a getter, such as a copper-based oxygen getter, that absorbs and stabilizes oxygen, nitrogen, and hydrogen levels, along with isolation valves and regeneration mechanisms to maintain a stable inert atmosphere, and removing absorbed gases and moisture generated during regeneration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional vacuum degassing and backfilling methods are used, then oxygen content can be reduced to low levels (e.g., 1000ppm), but oxygen content becomes inconsistent throughout the build process due to material absorption
Solution Approach 1:
The patent implements continuous gas recirculation through the build chamber, maintaining constant getter operation throughout the build process. This continuous action ensures consistent oxygen removal rates that match material absorption rates, preventing oxygen content fluctuations that occur with intermittent vacuum-backfill cycles.
Solution Approach 2:
The getter material automatically absorbs oxygen from the recirculating gas stream without requiring external control or intervention. This self-regulating mechanism maintains stable oxygen levels by naturally balancing absorption with material consumption, eliminating the need for manual atmosphere management.
2Reliability
If inert gas atmosphere is used to prevent oxidation, then hydrogen gas porosity occurs due to moisture absorption and hydrogen dissolution in material
Solution Approach 1:
The patent uses inert gas (argon or nitrogen) as the build chamber atmosphere to prevent oxidation of metal powder during processing. This inert environment protects reactive metal surfaces from reacting with oxygen while the getter simultaneously removes hydrogen and moisture to prevent porosity.
Solution Approach 2:
The getter acts as an intermediary substance that selectively removes hydrogen and moisture from the inert gas atmosphere. This mediator prevents harmful hydrogen transfer to the material while maintaining the protective inert atmosphere, solving both oxidation and porosity problems simultaneously.
3Quantity of substance
If nitrogen is used as inert gas, then oxygen content is controlled, but nitrogen absorption by material causes undesirable effects
Solution Approach 1:
The patent creates an inert atmosphere using either argon or nitrogen gas to prevent oxidation during additive manufacturing. When nitrogen is used, the getter system compensates for nitrogen absorption issues by maintaining excess nitrogen levels and removing absorbed nitrogen from the chamber atmosphere.
Solution Approach 2:
The patent adjusts nitrogen gas flow rates and recirculation parameters to compensate for nitrogen absorption by the material. By dynamically changing gas flow parameters and maintaining elevated nitrogen levels, the system compensates for absorption losses and prevents nitrogen-related defects.
4Stability of the object's composition
If getter is continuously operated to maintain stable atmosphere, then gas recirculation system complexity increases
Solution Approach 1:
The gas recirculation system performs multiple functions simultaneously: it cools the build chamber, removes oxygen through the getter, eliminates hydrogen and moisture, and maintains inert atmosphere composition. This multi-functionality justifies the system complexity by consolidating multiple atmospheric control requirements into a single integrated solution.
Solution Approach 2:
The getter material serves as an intermediary component that simplifies atmospheric control despite system complexity. It automatically regulates oxygen, hydrogen, and moisture levels without requiring complex sensors or control algorithms, providing stable atmosphere through passive chemical absorption.
5Quantity of substance
If vacuum degassing is performed before each build, then oxygen content is reduced, but build time is increased due to repeated vacuum and backfill cycles
Solution Approach 1:
The build chamber is evacuated to vacuum and backfilled with inert gas before the build process begins, and the getter is activated beforehand. This preliminary preparation creates a controlled atmosphere that maintains stable low oxygen levels throughout the build, eliminating the need for repeated vacuum cycles during manufacturing.
Solution Approach 2:
The gas recirculation system operates continuously throughout the build process, maintaining atmospheric composition without interruption. This continuous operation eliminates downtime associated with repeated vacuum-backfill cycles while keeping oxygen content consistently low through ongoing getter absorption.
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
The solution effectively reduces oxygen, nitrogen, and hydrogen levels to lower concentrations than conventional methods, ensuring consistent build properties and preventing hydrogen gas porosity, while allowing for the regeneration and reuse of the getter within the apparatus.
Implementation Method 1
a gas recirculation circuit with a getter, such as a copper-based oxygen getter, that absorbs and stabilizes oxygen, nitrogen, and hydrogen levels
Implementation Method 2
The getter may be an oxygen getter, such as a copper based getter. Oxygen is often absorbed by the material during solidification, especially in the case of metals.
Data Source
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AI summary
This invention concerns an additive manufacturing apparatus comprising a chamber (101), a build platform (102) movable in the chamber such that layers of flowable material can be successively formed across the build platform (102), a unit (105) for generating an energy beam for solidifying the flowable material, a scanning unit (106) for directing the energy beam onto selected areas of each layer to solidify the material in the selected areas and a getter (155) for absorbing oxygen, nitrogen and/or hydrogen from atmosphere in the chamber (101).