Layered Extrusion of Metal Alloys (LEMA)

Lead Research Organisation: University of Sheffield
Department Name: Mechanical Engineering

Abstract

Additive Manufacturing technologies are viewed as viable alternatives to conventional manufacturing processes, capable of creating geometrically efficient structures with low material waste. Commercial laser and electron beam metallic Additive Manufacturing systems are increasingly being used in high value aerospace and medical industries to directly manufacture metallic end-use parts. To manufacture components with full densities, these processes must completely melt the feedstock material, this subsequently generates large thermal stresses within formed components. Further to this, the hardware used within these high power laser/electron systems are inherently expensive and energy inefficient. This creates technical challenges and economic barriers that subsequently restrict new markets and industries from embracing this highly promising and disruptive manufacturing technology.

This proposal will develop a novel low thermal stress inducing, low cost metallic Additive Manufacturing process, Layered Extrusion of engineering Metal Alloys (LEMA). A specially created metallic feedstock will be extruded using a developed system designed to create layered 3D structures. A combination of unique feedstock chemistry and careful process control will allow efficient deposition of materials with a reduction in thermal gradients compared to conventional laser/electron based Additive Manufacturing systems.

Planned Impact

The LEMA process is a new innovate Additive Manufacturing method for directly forming metal structures. Because there is no requirement for complete melting of a metallic feedstock within the LEMA process, it possesses a number of advantages over currently available commercial metal Additive Manufacturing processes. The main benefits include a reduction in thermal stresses within formed components, lower system cost and higher energy efficiency. Other benefits potentially include a reduced shrinkage during solidification of parts, broader use of material feedstock with variable morphologies and further geometric freedom with creation of unsupported overhanging. LEMA opens up a new exciting area in manufacturing science and process methodologies which will appeal to many disciplines generating further publications.

The UK manufacturing industry is most likely to directly benefit from outcomes of this research. As previously mentioned the lower thermal gradients generated within the process will allow parts to be created with minimum distortion and potentially a reduced number of anchors or supports normally required within conventional laser or electron beam based systems. Further to this it may be possible to create unsupported geometries, this would present a distinct capability advantage allowing more geometric freedom for the process. This research will communicate the capability advantages of low thermal stress manufacturing of components to current manufacturers of metallic Additive Manufacturing systems and end users.

Due to there being no requirement to fully melt feedstock, the LEMA process system hardware is likely to be considerably lower cost compared to conventional laser or electron beam based metallic systems. This will make the process cheaper allowing new markets to gain access to this technology and benefit from the opportunities that Additive Manufacturing presents (new products/industries, efficient manufacturing, job creation etc.). The low system cost will also allow the UK to be more competitive in response to global trends and market drivers.

With energy prices on the rise companies are seeking to maximise efficiency and reduce energy consumption. Convectional laser/electron based metallic Additive Manufacturing systems are largely energy inefficient, the LEMA process is likely to a have higher energy efficiency as a result of its lower operating temperatures. This will reduce costs for manufacturing and in the long term will benefit the environment because of lower overall energy demands.

Publications

10 25 50
 
Description A system has been developed for the semi-solid extrusion of metals from irregularly shaped particulate feedstock and creation of 3D components. The materials (low cost chips or pellets) are mixed/blended and added into a heated chamber (heated using induction and conduction heating) maintained in an inert argon atmosphere. The materials are then mixed/broken up with a specially designed electron beam melted titanium screw to create a semi-solid mixture (some elements liquid others solid creating a specific liquid fraction ratio) and then extruded through a heated nozzle tip. The extrusion system sits within a 3-axis deposition head allowing net shape features to be fabricated. To date, mixtures of aluminium and copper have been successful extruded in a semi-solid form using this setup. For the process to extrude consistently it was vital that correct control over temperatures and shearing rate are maintained. This research is currently active/ongoing via a fully funded 3 year PhD project, with technical results expected to be published in late 2018
Exploitation Route Temperature and shearing control over feedstock have been identified as critical for successful extrusion using this process. An academic paper to be published in late 2018 will elaborate on this and highlight other technical challenges and design considerations for future iterations of LEMA (i.e requirement for positive gas flow within nozzle to aid extrusion, narrowing of material mixing chamber to aid temperature control, refined screw designs etc). To date a comprehensive understanding of using semi-solid extrusion to directly create 3D printed metal components from particulate feedstock is limited (with current works focusing on using wire feedstock from low temperature metal i.e tin/zinc). Future outcomes from this work will serve as an essential foundational footprint to further develop the science behind this process.
Sectors Aerospace, Defence and Marine,Manufacturing, including Industrial Biotechology

 
Description Invited guest speaker - 4th industrial revolution Ulsan, South Korea 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Present process development work undertaken within The University of Sheffield, with emphasis on new technologies (i.e Layered Extrusion of Metallic Alloys)
Year(s) Of Engagement Activity 2017
 
Description Invited key note speaker - Shanghai Additive Manufacturing Association (SAMA) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Presented additive manufacturing process development work (including layered extrusion of metallic alloys). Participants particularly interested in materials and properties of parts produced by LEMA and build rates compared to traditional metal 3D printing processes
Year(s) Of Engagement Activity 2017
 
Description Presentation at World 3D printing international conference China 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Presentation and discussion of collaboration opportunities with China (Infinite 3D). Presented process development work (including LEMA process). As a result of this meeting, Infinite 3D and Sheffield University created a new Additive Manufacturing Masters programme at the University. The MSc was initially setup with funds from Infinite 3D in a bid to attract students from China.
Year(s) Of Engagement Activity 2017
URL https://www.sheffield.ac.uk/mecheng/news-events/new-msc-1.675417