The following is an opinion piece written by Ian Falconer, Founder/CEO of Fishy Filaments.
At the end of 2015 I spoke at an Innovate UK event at Plymouth Marine Lab on the potential uses of 3D printing in the marine sector. It was a small but exclusive audience with representatives from companies and organisations with global reach and a presence at the extremes of engineering. Participants were there to understand and discuss how best 3D printing and its blue-chip brother, additive manufacturing, might be applied in and around the ocean, and contribute to a workshop on long term strategy in the field.
One of the main points I made was that a new machine called the MarkForged heralded a new era for low cost 3D printing in the marine sector because of its use of nylon, carbon fibre and kevlar to provide metal-like performance, but using only polymers. The machine itself was innovative, but it was the materials and the price of the machine that made the big difference.
I also talked about then recent advances in 3D printed morphing surfaces as means to adjust drag and grip, and the lack of research into materials toxicity with respect to biofouling.
But what seemed to grab the most attention was the idea that maritime ‘luxury’ had a business model that could be approached via 3D printing, where everything was bespoke and built to order, so long as the right materials were available to make aesthetically pleasing, as well as functional, forms. The idea that 3DP materials have a non-empirical value and can express ‘values’ had not occurred to most participants as a model upon which businesses could be built.
Since then, less than 2 years ago, hardware at the low-cost end of the market, the printer types that only use plastics, have sold approaching a million machines. Over 100% growth in sales of desktop 3D printers has been seen in 2016. New machines or components seem to be coming to market every month. The trends seem to be for bigger, faster, hotter, easier-to-use & cheaper. Alongside the hardware and software developments there new materials entering the market and plastics industry giants like BASF and DuPont are starting to add to the pace of change with their own 3D printing materials R&D units as industry starts to demand the plastics they are used to engineering with, but in 3D printer-ready form.
On the flip-side the machines able to produce metal parts still haven’t arrived at a price point where most individuals and SMEs can afford them, and the older technologies and well-known companies supplying them, such as Stratasys and 3DSystems, seem to be treading water in terms of technological advance. It remains to be seen if the entry of the BASFs and DuPonts of this world reinvigorates the high end of the market.
However, in my opinion, the commercial marine sector still doesn’t appear to have grabbed on to some fundamental opportunities lodged at the heart of fused filament 3D printing.
As I said in my talk these are two-fold; engineering and aesthetics.
I’m going to focus here on the engineering side of things where some of the structural weaknesses in the fused filament process that are exposed by engineering for dry land applications can easily be avoided when the end design sits on or in water. This means, hypothetically at least, it should be easier to build bigger structures for marine applications using fused filament deposition technologies than for dry land.
To dive a little deeper;
The fundamental paradigms for engineering larger structures on land or in the air are dominated by gravity and mass. That means that weight is always a cost, whether that is expressed through fuel efficiency, the amount of a material used in a design or the expense of a material to meet specific design tolerances. And because most metals are super-strong in tension (when being stretched) their use dominates designed materials when we engineer those larger structures for use in air. Of course non-designed materials such as earth & stone are an ever present in static ground-based structures.
Only at the very extremes of design do other materials, such as carbon composites, really get a look in, and then still by virtue of their own strength to weight ratio rather than any other factor, such as transparency, shapability or aesthetic appeal. At the extremes of engineering for use in air, everything kind of looks the same, to the point where even designers of mass-produced automobiles sometimes use cosmetic patches of carbon fibre mat to imply an association with high performance engineering.
Historically ‘tension’ has been a problem for fused filament 3D printing because the technology constructs each body by heat-welding layer on top of layer, and each layer boundry is a potential zone of weakness that can be pulled apart when enough extensive force is applied.
In water (a fluid 780 times denser than air at sea level) a far higher proportion of the dominant stresses are expressed through drag and compressive forces such as bouancy, rather than weight and tension. Put another way, the risk for sealed and pressurised underwater structures is usually implosion not explosion.
So where the layer-by-layer deposition of plastics can result in forms that fail more easily under undirectional extensive force than methods like injection moulding, those same fused filament methods should be more suited to withstanding multi-directional compressive forces, like those imposed on a sealed form submerged in water. Immediately low-cost 3D printing starts to look a better fit for marine engineering applications than has previously been expressed.
Of course nothing is perfect and you have to consider the orientation of the individual layers of plastic to avoid modes of failure parallel to the direction of layer deposition. However when you start to factor in the new materials and the requirement to use CAD software to design for 3D printing, a requirement that brings computational techniques like Finite Element Analysis within range almost for free, then you can start to optimise designs for compression and drag rather than extension and gravity.
Add in new printing methods such as syn-depositional fusion enabled by nanomaterials or graphene, post-depositional annealing by thermal or microwave treatment, and the desired ‘isotropic’ engineering performance is getting closer anyway. (NB; Some of these syn and post-print techniques look over-complex to me and I believe there are opportunities here too).
On the materials side we’ve seen that nylon and carbon fibre make a great team when used by the Markforged printers. But we’re also starting to see plastics that are marine sector staples, such as polypropylene (PP) reach the low-cost 3D printing market. I believe that the potential for large format 3D printing using PP is yet to be fully realised.
So, all the ingredients seem to be in place now; larger, faster, cheaper 3D printers capable of using engineering grade plastics, an increasing understanding of the different design challenges that the marine environment presents, and software that can simulate those challenges before we commit to build anything.
We should definitely be looking at using 3DP for use in the marine environment, not just making models using it. The Royal Navy is thinking about it and the US Navy is doing it.