Cooling Nozzle Control for Microstructure in Additive Manufacturing
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Solution Overview
Problem
Additive manufacturing techniques, such as direct energy deposition, face challenges in controlling residual stresses and microstructure due to geometry, build strategy, and material thermal expansion, making it difficult to achieve desired mechanical properties and surface finish.
Innovation Solution
The implementation of a controlled cooling system with adjustable cooling nozzles and forced convection to manipulate the convection heat transfer coefficient, directing cooling fluid towards the trailing edge of the melt pool and positioning nozzles strategically around the energy source to achieve a desired temperature gradient and microstructure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If direct energy deposition is used to fabricate complex components, then manufacturing capability and efficiency are improved, but residual stresses and microstructure control become difficult
Solution Approach 1:
The patent applies parameter changes by systematically varying cooling fluid flow rate, temperature, and application timing to control the thermal history of the deposit. By adjusting these thermal parameters, the process achieves desired microstructure and mechanical properties while maintaining high manufacturing efficiency through additive deposition
Solution Approach 2:
The patent implements preliminary action by applying cooling fluid to the substrate and deposit before the energy beam creates the melt pool. This pre-cooling establishes a controlled thermal gradient that prevents excessive residual stresses and guides microstructure formation during the rapid deposition process
2Stress or pressure
If cooling fluid is applied to control temperature, then residual stresses are reduced, but process complexity increases
Solution Approach 1:
The patent merges the cooling function with the deposition system by integrating cooling nozzles into the deposition head assembly. This combination allows simultaneous material deposition and thermal management through a single coordinated system, reducing overall process complexity while effectively controlling residual stresses
Solution Approach 2:
The patent implements feedback control by monitoring thermal conditions and adjusting cooling fluid parameters in real-time based on the thermal state of the deposit. This closed-loop approach automatically optimizes stress reduction without requiring complex manual intervention or additional sensing infrastructure
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 reduces residual stresses, refines the microstructure by reducing grain size and dendrite spacing, and enhances mechanical properties, such as yield strength, while allowing for complex geometry fabrication with improved surface finish.
Implementation Method 1
The plurality of cooling nozzles are operable to deliver a fluid flow to an adjacent surface of the substrate. The controller is programmed to determine a desired convection heat transfer coefficient based on a desired microstructure of the deposit and control the plurality of cooling nozzles to achieve the desired convection heat transfer coefficient
Implementation Method 2
During a direct energy deposition process, powder is injected from one or more nozzles into a focused beam of a laser. The localized heating melts a small area on the substrate and powder contacting the melt pool will also melt to generate a deposit on the substrate upon solidification
Data Source
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AI summary
An additive manufacturing assembly includes a substrate (26), a nozzle (30) for depositing additive material onto the substrate, and at least one cooling nozzle (40) for supplying a cooling fluid to at least a portion of the substrate. The at least one cooling nozzle is movable relative to the substrate. A controller (50) is operably coupled to the cooling nozzle. The controller is programmed to control operation of the at least one cooling nozzle to achieve a desired convection heat transfer coefficient of the additive material.