Technical experts at The National Robotarium have developed a sustainable system for recycling and repurposing plastic waste from 3D printers.

The UK’s centre for robotics and Artificial Intelligence at Heriot-Watt University is home to multiple 3D printers within its three distinct workshop spaces. The printers and other specialist machines are used daily by the facility’s engineering team, researchers and resident robotics companies.

With the price of printers and common materials, such as PLA (polylactic acid) filament, coming down in recent years, 3D printing is more accessible than ever. However, ease of production has created larger volumes of test and modular printing, increasing the amount of plastic discard.

Growing concerned about the large volumes of plastic offcuts being created in the workshops, Senior Technician for Robotics and Autonomous Systems, Thomas McGravie, and Senior Engineer Dr Alix Partridge were keen to explore ways to reuse the materials and reduce waste.

Compounding the issue further, leftovers from 3D printing cannot be easily recycled together, with different preparatory methods, such as drying or cleaning, required for different kinds of plastic.

Thomas, who oversees the workshops and technical spaces, said: “It was back in 2023, Alix and myself noticed that we were creating an astonishing amount of plastic waste through 3D printing; 54kg in two years!

“At the same time, I was talking to colleagues in other services and schools and found out that the Heriot-Watt is recycling 3 tonnes of plastic bottles a year. So, I wanted to come up with a way that we could repurpose the different types of plastic waste being produced on-campus.”

As part of his quest, Thomas looked online for inspiration, but found most solutions were either too costly or so time and labour-intensive that the benefits were negligible.

“I continued to browse online and stumbled upon someone in Australia who used a t-shirt press to flatten and melt down plastic shreds, reconstituting the 3d printed waste into sheets. Just by chance, one of our academics, Dr Alistair McConnell, had procured a shredder and injection moulding machine for a project, and he let us use these to recreate the first step of this process.”

However, despite now having the process knowledge and access to some of the required machinery, there was another factor getting in the way; time.

As Thomas explains: “Whilst we were keen to be more sustainable and reduce our carbon footprint, the demands our day-to-day jobs didn’t allow much time for experimentation.”

Fortunately, the discovery coincided with the centre hosting Fabio Tatti (Imperial College London) and Rob Woolley (University of York), two technicians from the UKRAS STEPS (UK Robotics and Autonomous Systems Strategic Technical Platform) network, who were interested in working on the filament recycling project as part of a week-long secondment.

The National Robotarium is a key delivery partner in the 3-year project, led by the University of Leeds and funded by the UKRI Engineering and Physical Sciences Research Council (EPSRC), that aims to strengthen the UK’s Robotics and Autonomous Systems capabilities and improve the long-term career prospects of Research Technical Professionals (RTPs).

Thomas said: “The visiting technicians were a fantastic support. Having four pairs of hands allowed us to fine-tune the system and produce more consistent heats and temperatures.”

The team presented on the project at the UK RAS STEPS Technical Showcase event, held at the London Science Museum in June, taking away the Highly Commended prize in the ‘Innovative Teamwork in Robotics’ category.

As well as facilitating the secondments, UKRAS-STEPS also provided financial support for the purchase of additional equipment, enabling Thomas and Alix to formalise the process and produce a template, which can be shared by other participating institutions across the UK.

“The support from UKRAS-STEPS has been vital to finessing the process. We are now able to recycle 3d printer waste into other items, such as badges and keyrings, which could be given to visiting school groups and work experience students. In time, we’re hoping to create items that are more commonly used in labs and workshops, greatly reducing the need to purchase these plastics as new.

“This has the potential to create a massive reduction in 3D printed plastic waste, not just at The National Robotarium but in RAS labs up and down the country.

Whilst the recycling system promises a sustainable and circular solution to plastic waste, Thomas thinks behavioural change is also needed to tackle the problem.

“We need to consider the reasons why we’re producing so much waste in the first place. Low costs and speedy turnaround times make it too easy to run off multiple prototypes in bulk – we need to be more mindful during the design process to not be wasteful and only print what we need.”