Additive manufacturing (3D printing) is often advertised as an alternative environmentally friendly solution for engineering applications as the part is made layer by layer, and it does not require excessive material to be removed using traditional manufacturing methods such as Computer Numerical Control (CNC) milling. Despite the fact that additive manufacturing reduces material waste, it cannot eliminate this issue, as some material will be wasted using brim, raft or support during the printing process. Moreover, the waste could increase if the print fails due to wrong print parameters or machine failure.

The situation could become even worse as the price of 3D printers has reduced significantly in the past few years, and as a result, more hobbyists are buying 3D printers for home, and because they are mostly amateur users, this could lead to potentially more plastic waste. For example, choosing the wrong print direction by the novice user could waste huge amounts of material on the support during print, which will later end up in the landfills. Therefore, recycling the additive manufacturing waste could significantly make the additive manufacturing process greener.

Recently, the Engineering Department at Lancaster University invested in an industrial grade recycling kit, using Secure Digitalisation (SecureD) University Enterprise Zone funding, that can be used to recycle plastic waste from additive manufacturing, which lowers the costs of industrial additive manufacturing and can create new plastics.

Of course, failed prints and prototypes will always be a source of waste; this is inevitable, especially with the number of projects that we run in the Engineering Department. However, recycling adds value to plastic waste by converting unused plastic into brand new, ready-to-use filament and turn Additive manufacturing into a closed-loop cycle of shred-it, dry-it and extrude-it. The majority of polymers are thermoplastics, which means that they can be melted or solidified via heating or cooling. Melting a polymer requires heating it until its macromolecular chains are free to move, after which the polymer can be reshaped. Extrusion, injection moulding, and 3D printing all do the same thing: they use heat to melt the polymer and give it a new shape by cooling it down.

A polymer extruder takes care of both the melting and forming of the polymer. The pellets/granulate are loaded into a hopper, which feeds the material into the extrusion screw made from hardened steel. This screw is placed within a cylinder, also known as a barrel. By rotation of the screw, the granulate is conveyed forward in the barrel, and heated.

We have tested the industrial grade recycling kit to produce high-quality Thermoplastic Polyurethane (TPU) filament. This extrusion experiment was extremely positive. Now various projects are proposed in the Engineering Department, such as producing 3D printing filament using plastic bottles, producing foam TPU for shoe insoles and recycling polylactic acid (PLA) with glass powder and carbon fibre, and we welcome ideas for more.

The advantages of recycling are numerous, ranging from environmental benefits to assisting organisations in finding more efficient methods to operate, making products and processes greener and cost-effective. Using industrial kit like this available at the University through our fully-funded collaborative research projects, including Greater Innovation for Smarter Materials Optimisation (GISMO) for businesses in Cheshire and Warrington, Expertise in artificial intelligence (AI) Foundry for businesses Greater Manchester and the Cumbrian Innovations Platform for businesses in Cumbria, which are all part-funded by the European Regional Development Fund, and others, businesses gain from both environmental and economic benefits, as well as the potential to build a favourable reputation among customers.

Our expertise in additive manufacturing and engineering is backed by comprehensive manufacturing technology capabilities that can help you investigate the filament recycling technique for the first time and help you to establish your in-house capabilities. If you want to put your ideas, materials, products and processes to the test, contact us to find out more about the available fully funded projects: www.lancaster.ac.uk/engineering/business.

Armin Yousefi Kanani is a GISMO Innovation fellow at Lancaster University. GISMO is part-funded by the European Regional Development Fund. To find out more about the project, visit www.smarter-materials.co.uk or email the project team at gismo@lancaster.ac.uk.

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