I think, by now, we’re used to snappy little videos about 3D printing.
Whether it’s the patron saint of shitty hip hop showing off a machine that may or may not use recycled plastic or some horrendously misdirected use of Europop to show off a gargantuan machine, there’s often very little in the way of meaty details – and that, as we all know, is where the devil lies.
Contrast that to this slick, short but ultimately, fascinating look into the collaborative work that’s being done by Lotus F1 and Boeing. As the video says, Boeing doesn’t have the rapid turn around for design, test, destroy, redesign, retest that a Formula 1 team does, but it does have a lot of specialist knowledge and spare carbon fibre!
What this video does is expose some of the work that the two companies have been doing to solve one of the ever present issues with 3D printing and in particular, sintering – all of which relate to the inherent weakness and lack of uniformity of mechanical strength/stiffness in additively manufactured parts.
This is one of the most commonly overlooked, but critical, issues with most 3D printed parts (particularly those not made out of metal which suffer much less from these effects) – anisotropy in the build process.
Or to put it another way, the parts that come off most 3D printers aren’t uniform in their structural strength. The very nature of the layer-based manufacturing process means that there’s inherent weakness in line with the layers.
One way of getting around this is to add in, particularly in sintered components, particles of other materials to boost that strength/stiffness. There’s aluminium, glass and carbon filled materials currently on the market from both the vendors and third parties (such as Windform by the CRP group over in Italy).
But according to those in the know, the issue is that due to the mechanical layer creation process and the use of a specific size of filler particles within the standard nylon powder used in sintering, the process creates parts that still have the fibres pointing is a specific direction.
So you’re back to inherent weakness in the parts, even with a ‘filled’ material.
The challenge that Boeing and Lotus have looked to solve, as the gent in the video says, is “how do you get that reinforcement to go in all different directions?”
If you’re not familiar with the ins and outs of sintering machines, they typically use a roller to distribute the powder for each layer. That process and the structure of the powder mean that the carbon fibre particles are essentially ‘combed’ into the same direction. That is enough to introduce anisotropic properties to the final built part that mean it’s less stiff in that direction.
New solution to an old problem
What Boeing and Lotus have done is step back, look at the process at the particle-level and worked out a method that uses the same process, but also adds in a second set of particles that are shorter in length and ground to a smaller size so that under the heated conditions in the machine, these secondary particles flow between those oriented particles and fill the part in a more randomised and uniform particle direction.
As I understand it, the nylon powder (typically) is manufactured with these smaller strands of carbon within them and these are then carried between those larger carbon particles. As a result, these secondary particles aren’t oriented in the same manner as the primary strands and this gives you an end result that is more controllable in terms of where strength and stiffness lie, but one which doesn’t suffer from the weakness inherent with more traditional forms of sintered components built using filled materials.
If you want to read up on what Lotus and Boeing are doing, the patent (US 2014/0050921 A1) can be found here.
Trust me, it will make your eyes bleed trying to work out what they’re actually doing.
What this shows is that while the mainstream media are still banging on about desktop 3D printers, there’s some truly innovative and collaborative work being done at the material end of the spectrum that will eventually filter into the mainstream market and make components manufactured with this material more reliable and more predictable.
It also shows that the future and growth of 3D printing is, as always, more about materials science and processing than it is about the hardware per se.