DED Enclosure Gas Recirculation for Heat and Soot Control
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Solution Overview
Problem
Direct Energy Deposition (DED) and Wire-Arc Additive Manufacturing (WAAM) face challenges such as high heat input leading to instability and shape generation difficulties, along with the issue of soot and smoke deposition affecting mechanical properties and weld stability.
Innovation Solution
A device and method utilizing a flexible enclosure with a process gas recirculation system that maintains an over-pressure between 2 and 50 mbar, using a sucking device to extract and re-introduce process gas close to the melt pool, and incorporating a cleaning unit to remove impurities, enhancing heat exchange and deposition rate while preventing contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high heat input is applied during DED/WAAM process, then material deposition occurs, but waiting time between layers increases and deposition rate is limited
Solution Approach 1:
The process gas is periodically extracted and re-introduced into the enclosure in controlled cycles, creating periodic convection currents that enhance heat removal during deposition while maintaining stable welding conditions
Solution Approach 2:
The pressure within the enclosure is maintained at a specific over-pressure range (2-50 mbar) to optimize gas flow characteristics and heat exchange efficiency, directly addressing the thermal management issue that limits deposition rate
2Manufacturing precision
If precise heat input is applied, then desired weld width and height are achieved, but process complexity increases
Solution Approach 1:
Process gas acts as an intermediary medium to transfer heat away from the weld zone. By controlling gas flow and pressure, thermal management is achieved without directly modifying the arc heat input parameters, simplifying the control system
Solution Approach 2:
A pneumatic system is used to control the extraction and re-introduction of process gas within the enclosure, providing precise pressure and flow control to manage heat transfer and maintain welding precision
3Productivity
If excessive heat input is applied, then material is deposited, but weld height decreases and width increases
Solution Approach 1:
The harmful excessive heat is converted into a beneficial effect by using process gas convection to selectively remove heat from specific zones. This allows high energy input for rapid deposition while maintaining precise weld geometry through controlled thermal management
4Productivity
If process gas is recirculated, then heat exchange is improved and deposition rate increases, but soot and smoke may be redeposited
Solution Approach 1:
Soot and smoke particles are extracted from the recirculating process gas stream before the gas is re-introduced into the enclosure. This removes harmful contaminants while maintaining the beneficial thermal management effects of gas recirculation
Solution Approach 2:
The process gas is discarded of its contaminants (soot and smoke) through extraction and filtration, then recovered and re-introduced into the enclosure for continued thermal management and atmosphere maintenance
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 improves heat management and deposition rate, reduces waiting time between layers, and maintains a clean, stable process atmosphere, enhancing the precision and quality of the additive manufacturing process.
Implementation Method 1
a sucking device configured to suck in part of the process gas and thereafter to re-introduce the process gas into the process atmosphere
Implementation Method 2
a welding torch configured to generate an arc for generating a melt pool on a surface of a workpiece
Implementation Method 3
the pressure within the enclosure is maintained at an over-pressure between 2 and 50 mbar
Data Source
AI summary
The present invention relates to a device and a method for DED or WAAM, comprising a welding torch configured to generate an arc for generating a melt pool on a surface of a workpiece, and a wire feeder configured to feed a wire towards the melt pool to generate a weld seam on said surface, and an enclosure enclosing at least part of the workpiece and comprising a process atmosphere with a process gas, wherein a sucking device sucks part of the process gas out of the enclosure and thereafter re-introduces the process gas into the process atmosphere, and wherein the enclosure comprises or consists of a flexible housing or a tent and in the sucking device is connected to a buffer volume or a pressure stabilizing unit.