Killer 3D Printing Applications: Variable Density Cushioning


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One of the biggest opportunities for 3D printing applications out there is variable density cushioning. This is a widely misunderstood area that could unlock multi-billion revenues for additive manufacturing (AM). One of the reasons for this is that, apart from an excellent effort at Ultimaker years ago, there is currently no meaningful cross-industry application development going on in material extrusion. Another reason is that there is so much shoe disinformation in the world that the true value is lost. Both these issues are clouding the significant opportunity that is variable density cushioning.

Application Development Success

While the options for material extrusion in variable cushioning is being forgotten, HP, Carbon, and EOS are doing an excellent job of gathering up cross-disciplinary skills and experiences to develop new applications with their partners. Working with materials companies and manufacturers as far afield as climbing shoes, outdoor outfitters, bike seats and basketball makers, these original equipment manufacturers (OEMs) are developing end-use applications that are centered around their technologies.

These three firms have realized that, in order to really move the needle for additive, they have to marshal a portion of the value chain to collectively develop breakthrough applications that give their technology 1., true volume replete with 2., margins and 3., marketing impact. That holy trinity could get these firms new streams of significant revenue tied to their platforms, as well as marketing, and knock on business development success. If they turn one sporting goods firm, the whole industry could pivot to additive for some components. If the 3D printing revolution isn’t as popular as first imagined, we should man the barricades. Or, perhaps in this metaphor, it would be more apt to consider the trio as being the only ones constructively working on tearing down the barricades to additive via breakthrough applications.

Cushioning Explained

The PRO/CESS bike seat. Image courtesy of Tim Schültze on Instagram.

One key area where 3D printing can play a difference is in cushioning for a wide variety of items, including the following:

  • head gear: helmets, visors, hearing protection, glasses, safety glasses, headsets
  • handles for sporting equipment, including handlebars and steering wheels
  • gloves
  • seats: for bikes, motorcycles, chairs, cars, truckers, delivery people, aircraft
  • headrests
  • backpacks
  • skis, skates, slippers, and shoes
  • gripping surfaces for all manner of sporting, assistive, and industrial equipment
  • prosthetics, braces, assistive equipment
  • computer mice and other peripherals

If we see cushioning surfaces as a single application, then it could eventually be one of the most high-volume and profitable 3D printing applications worldwide. There is a potential balance there between volume and margin protection, with firms becoming much like Gore. The $4.5 billion textile business is known for Goretex, which is expensive, highly functional, and the gold standard of breathable weather protection.

It will be a hard slog getting there, but the potential for 3D printing will be much larger than that. There are two particular areas where AM can outperform other processes: surfaces and cushioning. We will look at grip, wicking, and optimal performance of 3D printed surfaces in another post. Here we will only look at cushioning.

Shoe Interference

Generally, the 3D printing shoe opportunity is looked down upon, due to the huge gulf between cost levels of manufacturing shoes and those of additive footwear and insoles. I wholly agree. Most of the 3D printed shoe stuff going on is marketing fluff. It’s a great example of using a 3D print to anchor a cost-effective marketing campaign. However, I do believe that there are some real opportunities in shoes within the current economic paradigm as it relates to slippers, institutional shoes, specialized footwear and as a differentiator for certain low-volume, low-fashion-risk models. Eventually, when material costs are reduced significantly and truly automated 3D printing production is established, it will be possible to reduce costs in line with shoe manufacturers’ expectations. Conversely, someone could disrupt the existing shoe market by reducing their fashion risk and having better niche designs that are more timely, in line with the havoc that Zara´s Inditex has wrought on the fashion market. Now, these are all Hail Mary types of developments that could occur if the stars align. But, the gulf between the wishful thinking in footwear is confusing the future potential of the category.


BIOMIMICRY: 3D PRINTED SOFT SEAT (2014): a closer look at the material. Image courtesy of Dezeen.

Now, under the partial clouds of shoe disinformation, we can see the emergence of a peculiar element: the lattice. Lattices are extremely useful if you want to save weight on a non structural component somewhere. And we’re going to be surrounded by lattices in AM for—like—ever. They are the most obvious way to obtain cushioning while saving on material cost and print time in vat photopolymerization and powder bed fusion. Their super cool, distinctly 3D printed look means that designers, C-level types, and marketeers love them. There are plenty of amazing things that lattices can do, but they are very problematic and overused in a lot of applications.

The most positive thing I can say about lattices is that they’re the Prius of polymer additive in consumer applications so far. By now, you can see what is happening: the people tied to making lattices are making the lattices that marketeers love because their processes are in part tied to and identified with these structures. You will not believe just how lattice-centric the sketch of the future department is at the moment. It is difficult to predict the performance of a lattice under stress and repeated forces. After many and variable cycles of load, powder bed fusion and vat polymerization part performance degrades. Doubtlessly these issues will be ameliorated over time, but there is a better way.

No One in the Cell´s Corner

Material extrusion is a very cost effective 3D printing process, but since no one is really trying to develop the technology or performing any breakthrough application development in any significant way, no one is fighting for material extrusion in cushioning. Lattices abound, but cell shapes are ignored.

There have been few totally breakthrough moments in additive for me, but one such moment was when I saw the post from Steve Wood (aka “Gyrobot”) on variable density insoles in 2014. To me then, the shoe case could make sense if the right conditions could be met. With variable density insoles the squishiness, rebound and softness of a sole could be change at many individual points through varying the infill. With material extrusion you can print TPU, silicone or PP and then vary the thickness and pattern of infill to conform to a particular walking style, therapeutic need, back issue or tread. Through this innovation you can 3D print a unique at every point insole that can conform to your walking style or mend it. You can then get an insole that is uniquely comfortable that cannot be made with conventional manufacturing techniques.

Now, it will be a bit ugly, but you can use Dye Mansion or AMT technology to make it look better through vapor smoothing. You’d have to automate a 3D print farm of desktop machines to print these soles as well. It will, however, eventually be significantly less expensive than a 3D printed component made with other processes. Well in line with what could be profitable for high-end applications and insoles. You could ensure that soldiers experience less fatigue, that FedEx staff smile more easily towards the end of a long day, or that the employees at McDonalds perform their jobs more comfortably. In short, you could optimize walking performance in a way not shown yet. You could make it tougher at the part where your toe meets the sole, squishier in another area, and demonstrate less lateral motion in other parts, while being firmer towards the back, and having more cross motion in another part. In effect, you could make a completely unique sole to make the wearer more comfortable. If we look at all the firms that failed in shoe 3D printing none of them deployed this and many were tied to far too expensive components that did nothing for the user. Variable density insoles could change all that.

But…wait it gets better

But, we can do so much more. We can encapsulate air in each pocket. We can make the shape, amount and pressure of that air different. We can therefore go far beyond the performance and comfort advantages in air inside shoes seen so far. We can also customize air cushions just for you. We can also customize the infill pattern, the infill wall thickness, the infill fill, the geometry of the infill inside the infill pattern and we can do this at every millimeter. We can add different materials as infill and different for infill walls also. So we can create a unique material that goes far beyond what can be done with conventional manufacturing. And this could change the calculus of shoes and insoles. Now, we’d all have to get scanned and spend like a half an hour doing exercises on pads and cameras. That change in consumer behavior will be difficult. But, if you turn this into an event or desirable thing then it could move the needle for a certain segment in the shoe market. But, I think that selling to the police force, factories and other institutions would be much easier since you can sell them on lower fatigue and better performance.

Other Cushions

It would probably be far easier to look to other examples outside of footwear however. Now in some cases lattices, if their long term performance can be guaranteed could be better than cells. Lattices could let air pass through which is why applications such as bike seats and backpack cushions could be a win for them over material extrusion. Famously in helmets, we can design structures that can absorb fast impacts and slow heavy ones optimally through 3D Printing. Some of this may also be a win to powder bed of vat photopolymerization’s ability make these structures well. But for others the wider material selection and lower cost will probably make them a win for material extrusion. If humans are not lying down, they’re walking or standing and if they’re not doing that they’re sitting. In all of these cases we can improve the contact of the human with the world or with one thing in particular. In aircraft seats or prosthetics, we can change industries by designing unique materials that could give optimal long term comfort. Mattresses, office seats, wheelchair seats and others could be mass customized. Or they could be radically redesigned and updated.

In some cases radical form factor changes could impact industries by making another two rows of airline seats possible or by making cars roomier while keeping their volume. In other cases long term comfort will make the difference. Software tools could be used to radically redesign all the cushioning surfaces we can come in contact with. We can make much compact travel pillows that fold in on themselves and are more comfortable. We can make better industrial gloves, bike gloves and military gloves as well. We can make your sleep, walk to the office, car journey, sit down meeting better too. Wherever you are in long term or uncomfortable contact with the world we can make it better for you. And one of the best methods for that is to 3D print differing infill patterns, infill materials and structures, infill wall thicknesses at every point according to the optimal at that one point using Material Extrusion.

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