Over recent months we have seen a real change in the evolution of 3D printing technology. New 3D printing systems are being introduced every week, which are now relatively affordable, more energy efficient, compacted and, thankfully, quieter. But it is the availability of a range of new polymers that offers the most exciting aspect of 3D printing technology development. We are now leaving behind the traditional ABS and PLA, which we have grown accustomed to, fond of, and somewhat bored with. However, with innovative new materials, our boredom is about to change.

In our lab at Swansea Universities Welsh Centre for Printing and Coating (WCPC) we have started to trial these fascinating new polymers, testing them for durability, creep, and extrudability. We have had success with mixing metal and ceramic particles into polymers, which makes parts look and feel like real metal and ceramic parts respectively. The great thing is that even with fine particles mixed into them, these materials are still easy to extrude using standard 3D printing extrusion technology.

Thermoplastic Elastomer (TPE), going by the name of Ninjaflex, allows the fabrication of rubberized components, and it’s a fascinating filament (so is electrically conductive piezoresistive carbomorph, AKA. conductive ABS). By year’s end, we will see tenax-based carbon fibre filaments becoming common–and fibreglass material will soon follow, becoming available in 2015.

A few months ago, I heard about Taulman introducing Nylon 645 filament, which is essentially polyamide. This is a fascinating high strength material (UTS 320MPa), because it is both biologically compatible and inert. For about $20 you can procure about 0.5kg, which can subsequently be use to produce hundreds of exciting structural components.

One of the most exciting and closely watched new uses of this material is producing patient specific 3D printed implants.  These implants are used for occasions such as cartilage joint replacements; these procedures are often more difficult than bone replacements because the part must accurately conform to an existing internal bone structure and be pliable enough to conform to unusual mounting methods. These parts must be inherently strong to keep the joint from becoming misaligned by stress, and most importantly, they must provide a long term slippery surface to the biological mating surface. During this process, we produced a prototype cartilage joint replacement to trial this material. By carefully extruding Nylon 645 at a speed of 20mm/sec, and at an extrusion temperature of 250°C, we were able to produce a prototype precision implant.

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One of the most significant features of 3D printing is the ability to print a part that is difficult or impossible to make with a traditional CNC machine. This implant needs a number of intricate chambers for bone attachment, and these would be impossible to make without 3D printing technology. But, with the technology, in less than two hours the implant was produced–complete to ±25µm degree of precision. Take these features from just a lab experiment and scale this 1-5process up.  In theory, one could print sensitive electrochemical components and sensors within this implant as well. The newly printed and pliable implants do not split, break, or tear and can be machine-washed and dried many times.

Recently, surgeons and doctors from the Hague University have already determined Nylon 645 meets and exceeds the requirements to support several possible uses inside and outside of the human body. From bone replacement to electronic sensor enclosures, hospitals and clinics can now design, and subsequently print, on-demand patient specific support components.

In the past, a prosthetic was designed specifically for a patient’s shape, weight, and structure, requiring iterations of models and try-outs. With the combination of 3D scanning and on-demand 3D printing, a patient can now leave the hospital with a pliable prosthetic. These are designed specifically for their needs, while at the same time being built on what we determined could be a slightly modified low cost home 3D printer.

The interesting thing to note is that now 3D printing offers us the opportunity to start hi-tech enterprises, but in the style of old-school cottage industries. For the cost of perhaps under $800, one could start a custom medical implant business right at home. The real power of 3D printing is starting to be realized, and it is these materials which allow a whole affordable range of functional, integrated, and customized components made on demand.

Taulman 645 Technical Specifications1-3

645 Nylon Co-Polymer consists of the purest form of a delta transition of Nylon 6/9, Nylon 6, and Nylon 6T– with a crystallinity optimisation process in addition to post processing for maximum bonding during a 3D printing thermal transition process. Construction is from granule form through nylon extruding systems to a 12 station extrusion to draw, 4 chiller loops with 2 post processing stations to a final draw of 3mm or 1.75mm round line.

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Safety

Finally, Nylon 645 poses no public health concerns.  It meets the EU’s  Registration, Evaluation, Authorisation, and Restriction of Chemicals (REACH) requirements as defined by the European Chemicals Agency (ECHA). There are no additives or chemicals in 645 that are listed in the REACH Directive; it is non toxic and is “inert” to the body.

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Considering its widespread applications, affordability, and non toxicity, Nylon 645 has great potential for customized, 3D printed medical implants, such as those used in cartilage joint replacement surgeries.  The creation of implants and prostheses just grew more refined, thanks to emerging 3D printing technologies.

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