Metallic additive manufacturing applied in the filitration industry
Creators: name: Burns, Neil
Publisher: name: Lancaster University
Year: 2019

description: Filter media are essential in all industries to prevent contamination and damage of downstream processes as well as to perform separation processes. Filtration is required to remove particulates from fluid, liquid and gas, and for many industrial manufacturing processes mass produced filters do not provide a tailored filtration system to suit their requirements. Bespoke filtration solutions are needed. Customized metal filter production, where batch numbers are small, often from 1 off to a few thousand off, involves individual filter designs, particular tooling for each filter type, plate perforation, forming and welding of filter support as well as the many hand operations in mesh cutting and assembly. One advantage of this process is that the filter media can be tailored to suit operational pressures, environment type and filtration requirement. When a filter is placed in a pipe and fluid pumped through the filter, turbulence occurs and the resistance across the filter, known as the pressure drop, increases and more pumping energy is required. Design alterations may decrease the pressure drop across the filter, making the filter more efficient. Additive Manufacturing (AM) was identified as a technology that had the potential to create novel innovative filters designs that may have a reduced pressure drop. This thesis examines how additive manufacturing may be utilized as a tool to develop novel filter media. A literature review of the types of additive manufacturing technology was undertaken to understand the principles of layer by layer manufacturing. The technical challenges and potential defects in AM components were identified. The investigations in this research utilises Selective Laser Melting (SLM) a powder bed fusion AM technology. For powder bed fusion, the metallic powder, here Stainless Steel 316L (SS316L), has a particle size range of 15-45µm. This combination of sizes ensures a maximal packing within the powder bed, however the AM technology utilized here demonstrated an apparent nonuniform distribution of powder in the bed and this was investigated. Designs for novel filtration media that could reduce the turbulence of fluid flow were created using Design for Additive Manufacturing (DfAM) principles. A novel filter media with holes aligned to the fluid flow was created and the resultant pressure drop across the filter was tested in in a flow test rig. The AM filter design had a reduced pressure drop compared to a conventional filter equivalent. Having demonstrated that AM can be employed to deliver improved filtration, further novel filtration media were designed to increase the open area of the filter. Conventional manufacture of filter media typically comprises of a filter support and woven wire mesh, whose aperture is dependent on the wire diameter and weave. A novel filter 4 with integrated filter support and mesh was designed in a range of sizes. These filters were then tested for pressure drop at increasing flow rates and compared to conventional filters. Integrity of the structural build of these AM filters was carried out using X-Ray CT to determine if the latticework structure was fully formed and without high levels of porosity. Initial trials demonstrated that the AM filters delivered an improvement in filter function however light microscope examination of the latticework determined that the latticework did not have a maximal open area. Further work was carried out to optimize this design including CAD redesign of the repeating units and optimization of build parameters used to build the AM filters. The AM filters were then analysed for latticework strand size, aperture size and tested for overall strength and pressure drop. Surface finishing methods were then trialed for SS316L AM components. The design freedom of Additive Manufacturing has enabled design of novel innovative filtration media that deliver added value through improved function.