New additive manufacturing processes continue to emerge

Tabletop produced using rapid liquid printing (RLP) process (image credit: MIT and Steelcase)

The 3D printing and additive manufacturing (AM) industry is anything but static. New hardware platforms, materials and applications are emerging all the time, sometimes at a dizzying rate. This is only compounded if you also take into consideration the many different modifications and significant developments around existing additive hardware, not to mention the proliferation of pre-process AM-specific software and post-processing equipment.

In the last month, however, advances with additive processes have seen daylight, emerging from some of the world’s leading research institutions. Here, Disruptive Insight provides an overview of three notable process developments.

Rapid liquid printing from MIT
Massachusetts Institute of Technology (MIT) in the US is a renowned research institution when it comes to 3D printing and additive manufacturing across a number of its many centers and/or laboratories of excellence. The Self-Assembly Lab is one of these, led by Skylar Tibbits (who introduced 4D printing and is the editor-in-chief (EiC) of the 3D Printing and Additive Manufacturing journal) and Jared Laucks. The research team of the Self-Assembly Lab, which has been collaborating with Steelcase, a USA-based furniture company, introduced rapid liquid printing (RLP) last month. With emphasis on the fact that it is still in the development stages, the RLP process methodology is advanced enough to bring it into the public domain, it seems, and it is distinctly different from any of the layering techniques that users (or followers) of 3D printing are familiar with.

It’s worth repeating, this is NOT an additive layer-by-layer process, rather the RLP process ‘physically draws in 3D space within a gel suspension’ in a continuous motion. It is however, an extrusion method, whereby liquid polyurethane is discretely extruded into a vat filled with a gel material that acts as a support material, effectively ‘drawing’ the model shape within the gel. It is reported that the extruded liquid solidifies quickly and does not require UV curing along the lines of stereolithography (SLA) or digital light processing (DLP) 3D printing processes.

According to the research team, RLP has been developed to address a number of key barriers for existing 3D printing processes, specifically the ability to ‘combine industrial materials with extremely fast print speeds in a precisely controlled process to yield large-scale products.’

The collaboration with Steelcase explains the focus of the project on producing original, customized furniture pieces. This is undoubtedly a valid application, and it will likely find many other creative applications.

However, there is currently no visibility on precise material properties, or on the ability to produce solid parts, which might prove constrictive for industrial applications.

THREAD from the AMRC
A more industrially focused project has emerged from the Design and Prototyping Group of the Advanced Manufacturing Research Centre (AMRC), based in Sheffield, UK. This group has developed what they are calling ‘a unique hybrid 3D printing process that allows electrical, optical and structural elements to be introduced throughout an additively manufactured component during the build process.’ To be clear, this technology is not a standalone new process; it is, effectively, a unique add-on, but an intriguing one.

Dubbed ‘THREAD’, the premise is that products and components can now be manufactured with in-built, continuous connectivity and additional functionality passing through the X, Y and Z axes. THREAD is a fully automated process that is reportedly suited to a variety of additive manufacturing (AM) platforms.

According to AMRC development engineer and AM specialist Mark Cocking: ‘THREAD has scope to simultaneously add multiple industry-recognized threads of differing materials into one component, giving the component additional functions. This will open AM up to a greater variety of uses. It could be used across many sectors such as medical, aerospace and automotive, where weight and size of components is critical or where components would benefit from integrated data transfer and the protection of sealed connective tracks.’

With patent-pending status, THREAD also offers advantages for the manufacture of components requiring encapsulated electronics. Components such as those used in medical prosthetics, consumer electronics or structural components that require electrical connections and until now, would have been secured externally to the component. The nature of the ‘sealed’ conductive tracks could also be of benefit for components that may be sensitive to contamination from debris, corrosion or impact.

Mark Cocking further stated: ‘THREAD has [the] potential to be developed as an add-on technology for existing AM platforms and also [to be] incorporated into next generation AM technologies.’

Diode-based additive manufacturing from the LLNL
The DiAM (Diode-based Additive Manufacturing) process is the result of combining two older research projects at the Lawrence Livermore National Laboratory (LLNL). Insight into this process was originally published last month in Optics Express. DiAM uses high powered lasers and a metal powder bed, so readers would be forgiven for thinking ‘same old, same old’. In a way, yes, but it is also worth taking a closer look. This process looks to be doing for metal materials what the high speed sintering (HSS) process is doing with plastics.

According to the LLNL researchers, the DiAM process has demonstrated unprecedented build speeds—in metal—‘far beyond’ the powder-bed fusion (PBF) systems currently available on the market and at a much greater scale. In terms of the process itself, what makes this possible, according to lead researcher at LLNL Ibo Matthews, is the implementation of a customized laser modulator called an optically addressable light valve (OALV). The OALV technology itself was originally developed to smooth out and pattern high-powered laser beams for the National Ignition Facility (NIF), as part of a revolutionary laser energy optimization by precision adjustments to the radiant distribution (LEOPARD) system.

This LEOPARD system dates back to 2010, but it is only more recently that the OALV capabilities have been married up with LLNL’s research into high-power laser diode arrays. This technology combination is sophisticated enough to form whole layers of a part in one pass, rather than the serial tracing of the laser across the powder bed, one layer at a time, which is how most metal systems work. It is this capability that renders it significantly faster and more scalable than existing PBF processes.

In addition, the laser diodes that provide most of the energy for this process are claimed more cost-effective than the fiber lasers used in most of the commercially available PBF metal AM machines.

In terms of output quality, again the researchers claim it compares favorably with existing metal 3D printers. Moreover, DiAM has the ability to better control residual stress and material microstructures to ensure repeatable quality that can be monitored. 

About Rachel Park

Rachel is a passionate advocate of additive manufacturing/3D printing technologies and the industry that has sprung up around it. However, as the hype and hyperbole has gathered momentum, her aim is always to offer a reasoned voice in the midst of inflated expectations and to cut through the noise in order to provide a realistic outlook of how things are.