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        IMA

Material developments for 3D printing

Also, download this story from the electronic issue here

The 3D printing market is estimated to grow at 24% CAGR till 2022, with investment in services, materials and hardware to reach US$58 billion by 2022. While 3D printing has taken off in the aerospace, automotive, consumer, healthcare, E&E and biomedical industries, other sectors are being targeted, too, thus, the requirement for new materials.

New UV curable elastomers with better stretching

Elastomers have been used in a host of applications, due to their elasticity, resilience, and electrical and thermal insulation, for fabricating soft robots, flexible electronics and smart biomedical devices that require soft and deformable material properties to establish safe and smooth interactions with humans externally and internally.

However, to date, the most widely used silicon rubberbased elastomers require a thermal curing process that limits fabrication in traditional ways, such as by cutting, moulding and casting, which constrains design freedom and geometric complexity.

To enrich the design and fabrication flexibility, researchers have used 3D printing techniques, such as UV curing-based 3D printing techniques that solidify liquid polymer resins to 3D objects through patterned UV light, to fabricate elastomeric 3D objects.

Gammaflux

Nevertheless, most of the commercially available UV-curable (3D-printable) elastomers break at less than 200% (two times the original length), which makes it unsuitable for many applications.

Recently, researchers have developed a family of highly stretchable and UV-curable (SUV) elastomers that can be stretched by up to 1,100%, five times the elongation at break of any commercially available elastomer, and are suitable for UV curing-based 3D printing techniques.

This work is a collaborative effort between researchers from theSingapore University of Technology and Design’s (SUTD) Digital Manufacturing and Design (DManD) Centre, which is funded by the Singapore National Research Foundation (NRF), the Hebrew University of Jerusalem (HUJI), and the Campus for Research Excellence and Technological Enterprise (CREATE), also funded by the NRF.

Using high resolution 3D printing with the SUV elastomer compositions enables the direct creation of complex 3D lattices or hollow structures that exhibit extremely large deformation. The researchers also say that complicated geometric structures and devices, such as a 3D soft robotic gripper, can be printed in an hour.

Compared to traditional moulding and casting methods, using UV curing-based 3D printing with the SUV elastomers reduces fabrication time from many hours, even days, to a few minutes or hours as complicated and time-consuming fabrication steps, such as mould-building, moulding/ demoulding, and part assembly, are replaced by a single 3D printing step.

The SUV elastomers not only sustain large elastic deformation, but also maintain good mechanical repeatability, which makes them good materials for fabricating flexible electronics. To demonstrate this, the researchers fabricated a 3D buckyball light switch that still works after being pressed for more than 1,000 times.

The researchers say this new elastomer will enhance the capability of fabricating soft and deformable 3D structures, including soft actuators and robots, flexible electronics, and acoustic metamaterials.

New filaments from an unconventional extrusion process

Meanwhile, not satisfied with the performance of 3D printing filaments available on the market, a Dutch supplier of engineering filaments for 3D printing has developed an extrusion system and as a result, filaments boasting higher strength and printablility. Started by a father and son team, Jan-Peter and Jasper Wille, 3D4Makers says that its new filaments eliminate problems such as breaking and bubbling and better meet roundness and tolerance requirements in parts.

As for the extrusion process, standard filament extrusion equipment is water-cooled and the filament is dipped into a water bath at a set temperature to cool it down as it extrudes. This moisture degrades the performance of PLA and engineering plastics, says the team.

The extruder developed by 3D4Makers uses a multiplejet air system to precisely manage water-free cooling of the filament. With this, the company claims that parts printed 3D4Makers with its filaments feature higher impact resistance and achieve tighter tolerances in ovality and inner and outer diameters, than those made with conventional materials.

The company says it can also produce 3D printing filaments without plasticisers or other additives, many of which are approved for food-contact applications and are biocompatible or biodegradable.

The technology has found initial acceptance in research institutes, where PLLA and polycaprolactone (PCL) filaments are used for biofabrication of skin and organs.

It also offers “a unique PEEK grade with higher printability” and adds that “few companies have managed to make PEEK filament this successfully”.

In addition, the company offers PEI, PPSU, ASA and 100% pure PLLA (mainly for biofabrication and bioprinting applications). 3D4Makers also claims to be the first in the world to have developed PCL filament in two grades of 99% and 100% pure formulations. It says this non-toxic and biodegradable material is used mainly in medical research and is suitable for making custom braces, grips and prosthetics.

Optimised ABS and PLA grades

Spanish materials supplier Elix Polymers says it has optimised five ABS grades for 3D printing, with improved printing performance, low warpage, dimensional precision and high resolution.

It says some new grades have already been validated at filament producers, 3D printer makers and part manufacturers who use Fused Filament Fabrication (FFF) or FDM (Fused Deposition Modelling). Elix says it is already cooperating with several printer producers and 3D software providers to identify the right partners and create a database with validated filament producers.

It is offering technical support, including recommendations on correct processing setups: extruder screw design, drive and spool ABS-grades-3D systems. The objective is to obtain the filament with the best quality properties in typical thicknesses of 1.75 mm and 2.85 mm and validate the material to meet the requirements of the final application.

Meanwhile, US biopolymers maker NatureWorks has introduced a PLA, Ingeo 3D870, for filament manufacturers who have trialled the product and commend the ease of processing and printability.

Ingeo 3D870 is said to comply with chemical inventory listings in key markets in North America, Asia and Europe. Parts produced are said to exceed ABS 3D parts in impact strength and with post-print annealing, and NatureWorks says it rivals ABS heat resistance.

Though NatureWorks offers a general purpose PLA, it says 3D850 and 3D870 have been designed specifically for 3D printing, with good UV colour lightfastness, low yellow index, and additional heat and impact properties as a result of cyrstallisation.

Asian development trio

Singapore’s National Additive Manufacturing Innovation Cluster’s (NAMIC) portfolio, made up of Nanyang Technological University (NTU), the National Research Foundation and SPRING Singapore, was formed last year to help companies develop capabilities in 3D printing.

It has successfully established joint funding for 39 projects between companies and academic research institutions, with S$3.8 million from the government via NAMIC and S$2.8 million from the companies.

SUTD

Of the research projects in the works, NTU is working with a local 3D printing start-up focused on healthcare to develop tissue implants customised for patients. The new printer can print the supporting structure layer by layer and insert living cells to form a live tissue that could aid in the regeneration of particular tissues or organs.

Another research collaboration between the Singapore University of Technology and Design (SUTD) and Gilmour Space Technologies is looking at developing a 3D printer to produce prototype solid fuel mixtures for rockets, which is made up of two or more fuels comprising wax and plastics and is designed and printed in a way that provides the rocket with the required thrust, but in a more cost-effective manner.

With the barrier of entry being quite high, due to the high cost of printers/machinery and a lack of expertise in additive manufacturing, this is one way that organisations can reach out to educate and help link companies to research institutes that already have existing 3D printing machines and the technical know-how.

(IMA)


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