Advanced Powder Processes Hub – Recoupling manufacturing process development with materials science
Manufacture using Advanced Powder Processes Hub
Powder-based processes have the potential to provide low energy, low cost and low waste high-value manufacturing and help secure UK productivity and growth. Research being conducted at the Future Manufacturing Hub in Manufacture using Advanced Powder Processes (MAPP) is helping to deliver on that promise.
Iain Todd Professor of Metallurgy within the Department of Materials Science and Engineering at the University of Sheffield
Powders suitable for Direct Laser Additive Manufacturing (DLAM) must absorb laser energy efficiently to enable sintering or melting. A wide range of technologically important compounds are laser-transparent or reflective, and thus are excluded from the processable materials palette.
Addition of graphene and derivatives, such as chemically modified graphenes (CMG), can aid laser fabrication from such low absorbance compounds. In very small quantities, CMG can dramatically increase laser absorbance, thereby allowing for sintering or melting of a potentially unlimited range of materials, including ceramics, reflective metals, alloys and polymers.
MAPP has demonstrated that the addition of CMG into laser-transparent silica powder at just 0.2 wt% allows for its successful laser sintering. This finding has the potential to unlock the true versatility of DLAM as a universal manufacturing technology.
Our work in powdered-polymer AM is focused on understanding the ways in which materials behave in our processes. This in turn will allow us to maximise the quality and repeatability of the parts we produce, something that is particularly important to end-users of these techniques.
We have been working with Malvern Panalytical and Netzsch to investigate the use of advanced characterisation techniques for powdered-polymer AM, and have shown that we can use these techniques to identify variations in manufacturing behaviour between different material grades.
This work highlights the increasing relevance of material characterisation in manufacturing, as well as the benefits to be gained through academia-industry collaboration.
Some of our efforts have been focused on understanding how parts produced using our techniques perform in real-life situations including antibacterial functionality for polymer AM, performance in dynamic contact situations and the long-term behaviour of parts, identifying the effects of ultra-violet weathering and beginning to understand the underlying causes of the changes we’ve observed.
As powdered-polymer systems become increasingly significant, this understanding of how they perform in specific use cases will be an essential part of helping them achieve their full potential.
The Diode Area Melting (DAM) process seeks to overcome the challenge of limited productivity within current Powder Bed Fusion (PBF) systems and improve process thermal control.
DAM uses an architectural array of low power, fibre coupled diode lasers to process pre-deposited powder. The efficiently packed fibre arrays are integrated into a custom laser head designed to traverse across the powder bed.
Each laser diode is individually controllable, enabling selective laser processing of powder bed cross-sections and layered fabrication of 3D net-shape components. The operating wavelength of each of these lasers are shorter than standard PBF systems, the laser energy is more efficiently absorbed by the feedstock material allowing lower laser power to be used. This process is inherently scalable, significantly increasing productivity compared to PBF.
Recent work has shown further efficiency gains with the use of low-power blue laser sources and the potential to control melt pool solidification, creating novel customisable microstructures.
Learn more at www.mapp.ac.uk
MAKING AFFORDABLE TITANIUM ALLOY COMPONENTS A REALITY
FAST STEP 3 (Field Assisted Sintering Technology for Swarf Titanium to Engine Parts in 3 steps) is a £1.8m collaborative R&D project, part funded by Innovate UK, to reduce the cost of titanium alloy components.
Lower-cost access to lightweight titanium alloys will be a game-changer for the automotive industry, enabling manufacturers to reduce
the emissions their cars create, while keeping them affordable.
The automotive sector does not routinely currently use titanium alloys, due to the significant associated costs. However, the sector faces ever-increasing challenges in meeting emission targets and reducing vehicle mass. Titanium alloys can be part of the solution to these challenges, if the cost can be reduced.
In the coming decades, the aerospace sector will generate vast and increasing quantities of titanium alloy swarf, which is essentially a waste product.
The FAST STEP 3 project will show it is possible, with appropriate cleaning and grading, to recycle this waste swarf as a feedstock for the FAST-forge process (developed at the University of Sheffield) to produce near-net-shape parts that are then lightly machined into finished components. This combination of low-cost feedstock with cost-effective processing means affordable titanium alloy components will become a reality.
Access to equipment provided by the Henry Royce Institute is proving vital for this project.
The aim is to demonstrate the production of titanium alloy components at 20% of the current cost and with minimal wastage. The project also aims to develop a new UK supply chain to exploit this technology; allowing diversification for companies within the traditional metal manufacturing sector.
Led by Bentley Motors and pulled together by the Northern Automotive Alliance, other consortium members are the University of Sheffield, Force Technology, Transition International and W.H. Tildesley.
2D NANOMATERIALS ARE UNLOCKING NEW PROCESSING OPPORTUNITIES
Robocasting is a 3D printing technology based on the continuous extrusion of a paste (or ink) to build parts layer by layer. These pastes should flow through a narrow printing nozzle (usually 0.1-1 mm in diameter) and then sustain the weight of the printed part.
Graphene oxide (GO) can act as a universal additive to manipulate the viscoelastic response of particle suspensions and formulate water-based robocasting inks for room temperature printing.
Due to its amphiphilic nature and 2D structure, it stabilises suspensions and modifies the flow and viscoelasticity of pastes containing particles with different chemistries (from ceramics to metals or polymers), and morphologies.
This is in part due to the similarities between GO and clay. Both exhibit flake-like shapes with different functionalities on their edges and faces that lead to the formation of networks. However, in the case of graphene oxide, the amounts required for this are much smaller. After printing, GO can be eliminated or retained to add functionalities to the materials.
We very often think of new 2D nanomaterials as part of composites and devices that take advantage of their unique properties. This work demonstrates that they can also serve as processing additives and open new opportunities in manufacturing.
ADVANCING DEEP TISSUE IMAGING
Research by a team formed by Profesoor Peter Lee, who leads the MAPP in-situ synchrotron imaging activities, has enabled intact human organs to be scanned and image in unprecedented detail. The application of this technique to image the damage to a 54-year-old male Covid victim’s lungs is shown above.