DED Process Gas Recirculation for Faster WAAM Layer Deposition
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Solution Overview
Problem
The high heat input during Direct Energy Deposition (DED) or Wire-Arc Additive Manufacturing (WAAM) processes leads to long waiting times between layers, limited deposition rates, and instability in weld processes due to excessive heat generation, as well as the production of soot and smoke that can contaminate weld seams and affect mechanical properties.
Innovation Solution
A device and method for DED/WAAM that utilize a flexible enclosure with a process gas recirculation system, where part of the process gas is sucked out and re-introduced close to the melt pool, maintaining an over-pressure between 2 and 50 mbar to prevent enclosure collapse and 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 invention converts the harmful excessive heat that causes long waiting times into a beneficial pre-heating effect. By actively recirculating the hot process gas back to the enclosure, the heat that would otherwise be wasted is now used to preheat the workpiece surface and surrounding area, reducing the thermal shock during subsequent deposition and allowing faster layer transitions.
Solution Approach 2:
The process gas recirculation system maintains continuous thermal energy utilization. Instead of allowing the hot process gas to dissipate into the environment between layers, the system continuously recirculates it back to the enclosure, ensuring that thermal energy is constantly reused to maintain optimal deposition conditions and reduce idle waiting time.
2Manufacturing precision
If excessive heat input is applied, then material is melted, but weld width increases and weld height decreases
Solution Approach 1:
The recirculation system directs hot process gas specifically to the enclosure containing the workpiece and melt pool area. This creates a localized thermal environment that concentrates heat where needed for material deposition while avoiding excessive heat diffusion to surrounding areas, thereby maintaining precise control over weld width and height.
Solution Approach 2:
The system dynamically adjusts the thermal parameters by recirculating process gas at controlled rates. This allows optimization of the thermal field distribution, maintaining appropriate temperature gradients that favor vertical weld growth (height) over lateral spread (width), thus improving dimensional precision.
3Productivity
If multiple weld seams are deposited on top of each other, then 3D structure is built, but heat accumulation causes process instability
Solution Approach 1:
The continuous recirculation of process gas provides sustained thermal management throughout the multi-layer deposition process. The system maintains consistent thermal conditions in the enclosure, preventing heat accumulation-induced instability by continuously redistributing thermal energy and avoiding localized overheating that would compromise weld quality.
4Productivity
If process gas is recirculated, then heat exchange improves and deposition rate increases, but enclosure pressure may become unstable
Solution Approach 1:
The system incorporates pressure sensors and control mechanisms that continuously monitor enclosure pressure during gas recirculation. When pressure deviations are detected, the system automatically adjusts recirculation flow rates or activates pressure equalization mechanisms, creating a closed-loop control system that maintains stable pressure while benefiting from improved heat exchange.
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 recirculation and cooling of process gas improve heat exchange, reduce waiting times, increase deposition rates, and prevent soot and smoke contamination, thereby stabilizing the weld process and maintaining desired material properties.
Implementation Method 1
part of the process gas is sucked out and re-introduced close to the melt pool, maintaining an over-pressure between 2 and 50 mbar
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, preferably between 2 and 25 mbar, preferably between 5 and 20 mbar
Data Source
Figure 1
AI summary
The present invention relates to a device and a method for DED or WAAM, comprising a welding torch (1 ) configured to generate an arc for generating a melt pool on a surface of a workpiece (2), and a wire feeder configured to feed a wire towards the melt pool to generate a weld seam on said surface, and an enclosure (4) enclosing at least part of the workpiece (2) and comprising a process atmosphere with a process gas, wherein a sucking device (5) sucks part of the process gas out of the enclosure (4) and thereafter re-introduces the process gas into the process atmosphere, and wherein the enclosure (4) comprises or consists of a flexible housing or a tent and in the sucking device (5) is connected to a buffer volume or a pressure stabilizing unit (10).