The rise of 3D printing robots

Materials World magazine
,
1 Oct 2017

Additive manufacturing has worked its way into the public consciousness – embedded as one of the foremost technologies of the day. But what is the next step? For some, it’s mobile manufacturing, as Gary Peters reports.

They are not your ordinary spiders, nor are they likely to frighten those with a mild form of arachnophobia. Rather, they are robotic and not at all fear inducing – developed to define the future of additive manufacturing.

Researchers at Siemens’ Corporate Technology’s Princeton campus, New Jersey, USA, have created the Siemens Spiders, also known as SiSpis, in an effort to jump-start the incorporation of mobile manufacturing into everyday society. Siemens describes them as autonomous additive manufacturing devices with legs.

In March this year, Livio Dalloro, the head of the Product Design, Modelling and Simulation Research group in the Automation and Control Technology Field at Siemens Corporate Technology (CT), told of how SiSpis ‘are part of a larger picture that we define as Siemens Agile Manufacturing Systems (SiAMS), and they represent the core of our autonomous systems research here in Princeton’.

He added, ‘We are looking at using multiple autonomous robots for collaborative additive manufacturing of structures, such as car bodies, the hulls of ships and airplane fuselages.’ 

Into the unknown

It’s bold, brave and, undoubtedly, challenging, as Dalloro’s comments to Tech Insider in April demonstrate, when he spoke of how the SiSpis project is one of the ‘first attempts in mobile manufacturing that will enable us to fabricate objects in places that we simply could not have built within before’. The SiSpis project is currently printing in a mixture of cornstarch and sugars, powered by lithium batteries, positioned on the legs of the bots. 

Each spider bot is fitted with cameras and a laser scanner to understand the environment in which they are operating. An algorithm, developed in-house by Hasan Sinan Bank, Research Scientist at Siemens CT, allows the robots to collaborate on a given particular task. 

Siemens’ CT division says each spider is aware of the length of its 3D printing device, or leg, and subsequently what area it needs to work on. The team behind the idea describes it as an individual box, which defines the task for each robot. ‘Each spider is capable of manufacturing only a small portion of a work piece,’ explained Bank, in March. ‘We are therefore trying to conceptualise and optimise the kinds of collaboration these robots should engage in.’ 

Speaking to Materials World, Bank outlines how people should think of the spider bots ‘as an experimental approach’ – experimentation today to understand what path they will follow in the coming years.

‘The ability to combine mobility and manufacture will have lots of other advantages,’ he adds. ‘For example, enabling manufacturing in austere or hostile environments, or somewhere we cannot go [such as Mars]. We can send robots, similar to [the spider bots], and use the materials on the surface.’

Speaking of materials, Bank explains that the use of cornstarch and sugars was mainly for safety and to develop their understanding of the overall system, and identifies composites and metals as materials of interest for mobile 3D printing. 

He adds, ‘It's also about the use cases. In future, cement might be another option. However, we need to scale-up the system. Those are the materials I'm thinking of. How soon? That depends.’

Bank is wary of putting timescales on the bots’ application. For example, when could they manufacture the hull of a ship? How many spider bots would be required? 'It depends on how big the ship is,’ says Bank. ‘If you are talking about something like a small boat, I think you would need about five or six robots. I cannot give an exact date for that.

'How are we going to realise it and when will that be? We are always trying to chase the most realistic thing, to have something real. It might be five years [until industrial scale]. First, you need to have the solid business case and appreciation of the complexity.’

Questions, naturally, will continue to be asked about the feasibility of such plans and just how far the spider bots can go. But Siemens is not the only organisation dipping its toe in the water. 

‘The possibilities are endless’

In 2013, Robert Flitsch had an idea. The mechanical engineer, who graduated from Harvard’s John A Paulson School of Engineering and Applied Sciences, USA, in 2015, was fed up with the ‘limitations of 3D printing’.

'You can think of a 3D printer as a box – the automation, the distribution elements, they really exist in this box,’ he tells Materials World. Enter Addibots, Flitsch’s ambitious plan to ‘combine robotics with 3D printing and break free from the limitations’. How? By creating small robotic devices – each one known as an Addibot – that incorporates an array of nozzles. Simply put, it’s a 3D printer mounted onto a moving robot.

Flitsch formed the company Addibots in 2013 and has since developed five generations of the devices. ‘Addibots combine three main systems – mobility, computer vision and additive manufacturing distribution. Early on, we realised how powerful this can be as a tool for different forms of construction. When you're moving these elements, you can use materials that interface into the surfaces you are printing on.’

The first use of an Addibot came when Flitsch tested it on ice, using water just above freezing on an ice hockey rink. Since then, the focus has been narrowed to, for the time being, road maintenance – fixing potholes, cracks and so on. An Addibot, says Flitsch, would use its mobility to move around its workspace, i.e. the road, and while moving, use computer vision to ‘see and characterise where the potholes are’, before manufacturing the repair. ‘The main challenge is really the heart of what an Addibot is – how do you combine all of these systems to work together?’ Flitsch adds. 

It’s a conundrum that Addibots is tackling step-by-step to prove the individual viability of the components, and Flitsch is constantly tweaking and fine-tuning. However, there’s also the material challenge. If road maintenance is going to be the arena that first welcomes the Addibots, then it needs to be seamless for all involved.

Flitsch acknowledges this. ‘What materials do you need?’ he says. ‘You're looking at asphalt first and you have to adapt this to work in this 3D printing paradigm. There are the functional and market aspects. 

‘You want to have the technology work in a way that people can use their existing materials. We are 3D-printing asphalt. I've already used the technology to fix some cracks on my own driveway. There are challenges to using these materials but I also see limitless possibilities.' 

That’s one driveway fixed, but the technology is yet to be introduced on an industrial scale. This is a question of funding and proving the concept does what it says on the tin. ‘We've really come a long way in achieving proof of concepts for a lot of the main aspects of the technology,’ says Flitsch. Now it’s just a case of getting that final push, which could be sooner rather than later.

Flitsch explains, ‘We're pursuing funding to achieve the final development that gets us to the industrial scale and out to market. We see it as being possible within one to three years. There are many maintenance problems that Addibots can solve in the short-term, so we can expect to get something into the hands of companies in that timescale.’

That is the task at hand, but the ambitious Flitsch is not content with standing still. ‘Addibots will be suitable for so many construction industries and making additive manufacturing mobile. You could use them to build boats, bridges, even houses. The possibilities are endless.’

MIT’s robotic arm

At the Massachusetts Institute of Technology (MIT), USA, the scale is bigger – the invention, known as the Digital Construction Platform (DCP), would fill an average car-parking space. 

At its heart, the MIT system, for which research began in 2011, is a robotic arm, designed to print the basic structure of a building. ‘The construction industry is still mostly doing things the way it has for hundreds of years,’ explained Steven Keating, a mechanical engineering graduate and former research affiliate in the Mediated Matter group at the MIT Media Lab, to MIT News in April. ‘The buildings are rectilinear, mostly built from single materials, put together with saws and nails. We wanted to show that we could build something tomorrow that could be used right away.’

MIT’s robot is a tracked vehicle, incorporating the robotic arm. This, in turn, has a smaller arm at its end that sprays the material for the structure. 

MIT claims that the arm can be ‘used to direct any conventional (or unconventional) construction nozzle, such as those used for pouring concrete or spraying insulation material’.

In the corresponding paper, Toward site-specific and self-sufficient robotic fabrication on architectural scales, published in the Science Robotics journal, Keating and Julian Leland and Levi Cai, research assistants in the Mediated Matter group, and Neri Oxman, group director and associate professor of media arts and sciences at MIT Media Lab, describe the benefits of mobile manufacturing, ‘Mobility rapidly becomes imperative as researchers seek to develop systems with much larger build volumes, to enable fully autonomous on-site fabrication, and to effectively deploy automated construction systems in swarm configurations.’

The decision to incorporate an arm, therefore, seems obvious – it’s mobile and has the flexibility Keating and colleagues desired. The dexterity of an arm, the research paper adds, makes it possible ‘to perform more sophisticated operations and adapt to varying construction environments’. In addition, an arm system has ‘a very large ratio of physical reach to platform footprint, enabling simpler access to complex sites and allowing extremely large work volumes’.

Last year, MIT undertook a test run. The robotic arm was able to print the walls of a 15m-diameter, 3.6m-high dome by fabricating a foam-insulation framework. It used Dow Chemical’s Froth-Pak insulation foam, often used in construction for thermal insulation. 

The actual printing time was 13.5 hours, although it took two days to complete the dome, because of lost encoder counts on the rotary encoder and delays when a layer of dew formed on the printed foam. In terms of energy consumption, an electrical drive system, which draws power from solar panels, was fitted to the DCP.

It’s a positive start, although there is some way to go before Keating’s dream ‘to have something totally autonomous, that you could send to the moon or Mars or Antarctica, and it would just go out and make these buildings for years’, comes to fruition. 

Much like the work at Siemens and Flitsch’s Addibots, there’s a long road ahead.