Coanda Flow Device for Additive Manufacturing Condensate Removal
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Solution Overview
Problem
In additive manufacturing processes like selective laser melting (SLM) and selective laser sintering (SLS), condensate accumulation in the build chamber leads to undesirable effects such as porosity and strength variations in the manufactured components and can block the laser beam path, necessitating effective condensate removal.
Innovation Solution
A flow device with a Coandă surface and passageway connected to a pressurized gas source is used to generate a laminar gas flow through the build chamber, utilizing the Coandă effect to create suction and improve condensate entrapment and transport, reducing turbulence and ensuring uniform gas flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If gas flow is introduced through a conventional rail to remove condensate, then condensate removal is achieved, but gas flow uniformity deteriorates due to frictional losses along the rail length
Solution Approach 1:
The invention extracts the gas flow generation function from a conventional rail system and relocates it to a Coandă surface positioned adjacent to the build chamber window. This removes the source of frictional losses along a long rail while maintaining condensate removal capability through a localized Coandă effect-based flow generator.
Solution Approach 2:
The Coandă surface acts as an intermediary device that generates controlled gas flow by utilizing the Coandă effect - where a jet of gas flowing over a curved surface creates a low-pressure region that draws additional gas along the surface. This intermediary mechanism produces uniform laminar flow without the frictional losses inherent in conventional rail systems.
2Productivity
If gas flow is increased to improve condensate transport, then condensate removal efficiency is improved, but turbulence increases causing positional variation in porosity and strength
Solution Approach 1:
The Coandă surface employs a curved geometry that guides the gas jet along its contour. This curvature is essential for generating the Coandă effect, which naturally promotes laminar flow attachment and reduces turbulence compared to straight or angular flow paths, thereby maintaining component property consistency while achieving effective condensate removal.
Solution Approach 2:
The invention utilizes pneumatic principles by introducing a pressurized gas source that generates a controlled jet flowing over the Coandă surface. The gas flow rate can be optimized to achieve sufficient condensate transport while the Coandă effect inherently stabilizes the flow regime, preventing excessive turbulence that would cause property variations in manufactured components.
3Object-generated harmful factors
If conventional gas blowing is used to remove condensate, then condensate is transported from the chamber, but turbulent flow causes positional variation in build properties
Solution Approach 1:
The invention replaces the conventional mechanical gas blowing system with a Coandă effect-based flow generation system. Instead of forcing gas through a rail or directly into the chamber (which creates turbulence), the Coandă surface utilizes fluid dynamic principles to generate attached, laminar flow that achieves condensate removal without the harmful turbulent effects on build properties.
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 enhances the removal of condensate from the build chamber, resulting in components with lower porosity and higher compressive strength, while preventing condensate from settling on the window and affecting the laser beam, thus improving manufacturing consistency and accuracy.
Implementation Method 1
the jet of gas (or so called 'Coandă jet') directed over the Coandă surface is pulled towards and travels along the surface by virtue of the Coandă effect, which, in turn, generates suction that draws additional gas into the space adjacent the surface
Data Source
AI summary
An additive manufacturing apparatus including a build chamber in which an object is built and a flow device. The flow device comprises a body having a Coand{hacek over (a)} surface and a passageway connectable to a pressurised gas source. The passageway has an opening located adjacent to the Coand{hacek over (a)} surface to, in use, direct a jet of gas over the Coand{hacek over (a)} surface. A space adjacent the Coand{hacek over (a)} surface is in fluid communication with the build chamber such that gas drawn into and/or propelled from the space causes gas flow through the build chamber.