Powder Bed Fusion Gas Filtration for Continuous Filter Switchover
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Solution Overview
Problem
In powder bed fusion processes like selective laser melting (SLM) and selective laser sintering (SLS), the removal of processing emissions such as condensate and spatter particles from the build chamber is challenging, as they can interfere with the laser beam and affect the quality of the workpiece, and existing filter systems may introduce oxygen and moisture during filter element changes, disrupting processing conditions.
Innovation Solution
The method involves connecting filter assemblies in parallel or series within the gas circuit, allowing for controlled gas flow distribution between unused and used filter elements, where the unused element is initially exposed to processing emissions to populate it, then used to filter emissions, thereby enhancing filtering efficiency and reducing adverse effects on the process. This includes a blended switchover of gas flow to ensure continuous operation and extend the life of filter elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If filter assemblies are connected in parallel to allow continuous operation during filter element changes, then productivity is improved, but device complexity increases due to the need for multiple filter assemblies and switching mechanisms
Solution Approach 1:
The filter system is divided into multiple independent filter assemblies (first filter assembly and second filter assembly) that can operate independently. Each assembly contains its own filter element, allowing one to be serviced while the other remains in service, enabling continuous operation without shutting down the gas circuit.
Solution Approach 2:
The system incorporates dynamic switching capability through a valve system that can redirect gas flow between the first and second filter assemblies. This dynamic configuration allows the system to adapt between different operational states (one filter active, both filters active, or switching between filters) based on maintenance needs.
2Reliability
If unused filter elements are exposed to processing emissions to populate them, then filtering efficiency is improved, but this requires additional time and operational steps
Solution Approach 1:
The system performs preliminary action by exposing the unused filter element to processing emissions during the initial phase of operation to populate it with particles. This pre-conditioning is done automatically as part of the normal operational sequence, allowing the filter element to be ready for service without requiring separate manual preparation steps.
Solution Approach 2:
The gas flow continues uninterrupted through the filter system while the unused filter element is being populated. The valve system maintains continuous gas circulation, and the filtering function remains active throughout the population process, eliminating any shutdown or idle time.
3Stress or pressure
If gas flow is distributed between multiple filter assemblies, then the pressure difference across each filter medium is reduced, but the valve system complexity increases
Solution Approach 1:
The valve system provides localized control over gas flow distribution to each filter assembly. By independently regulating flow to the first and second filter assemblies, the system can optimize the pressure difference across each filter medium based on its specific condition and capacity.
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 effectively mitigates the interference of particles in the laser beam, maintains processing conditions, and extends the life of filter elements by preconditioning them with emissions, ensuring consistent and uninterrupted powder bed fusion processes.
Implementation Method 1
A filter in the gas circuit filters condensate from the recirculated gas
Implementation Method 2
introducing a gas flow through the chamber in which the condensate, spatter and other particles are entrained
Implementation Method 3
Portions of the powder layer corresponding to a cross-section of the workpiece to be formed are then solidified through irradiating these areas with the beam. The beam melts or sinters the powder to form a solidified layer.
Data Source
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AI summary
This invention concerns a method of filtering gas in a powder bed fusion apparatus, in which an object is built layer-by-layer by selective solidification of a powder bed, and a powder bed fusion apparatus for carrying out the method. The powder bed fusion apparatus comprises a build chamber (101) for housing the powder bed (104), a gas circuit for recirculating the gas, including passing the gas over the powder bed within the build chamber, a plurality of filter assemblies (230a, 230b) in the gas circuit for filtering process emissions from the gas recirculated through the gas circuit and a valve system (123 a, l24a. l23b, l24b) operable to regulate a flow of the gas to each one of the filter assemblies (230a, 230b). The method may comprise controlling the valve system (123 a, l24a. l23b, l24b) to divide the gas flow between a first one of the filter assemblies (230a, 230b) housing an unused filter element and at least one second one of the filter assemblies (230a, 230b) housing a used filter element such that less gas flows through the first filter assembly (230a, 230b) than the or each second filter assembly (230a, 230b). The method may comprise controlling the valve system (123 a, l24a. l23b, l24b) such that a first one of the filter assemblies (230a, 230b) housing an unused filter element is connected in series in the gas circuit with at least one second one of the filter assemblies (230a, 230b) housing a used filter element such that the gas passes through the filter elements of both the first and second filter assemblies (230a, 230b).