Explained: Desktop Metal's FreeFoam 3D printing and DuraChain resins

3D printing news
2022
07/05
20:56
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In the corner of a mammothbooth at RAPID + TCT, amiddisplays of over 300 3D printed parts from metal jewellery to light fixtures made from recycled wood, Desktop Metal quietly introduced FreeFoam, a new 3D printing technology that enables the production of expandable foam products.

This latest material developmentis the product of the company's recently launched DuraChain family of photopolymers,developed by Adaptive 3D, which was brought into the Desktop Metal familyduring a succession of major acquisitions throughoutlast year. These resins are said to provide 'breakthrough elastic and tough material properties' for digital light processing (DLP) printing, specifically ETEC's Xtreme 8K machine,and open up newadditive manufacturing (AM) applications in industries such as automotive and consumer goods.

On the show floor in Detroit, TCT spoke to Walter Voit, President and CEO of Adaptive 3D to find out more.

LG: Talk to meabout FreeFoam.


WV: FreeFoam is a new class of materials that ispart of our DuraChain family of resins. It represents a class of printable photopolymers that have properties that the world hasn't seen before. What drives them is a technique that we pioneered with a lot of DARPA funding back in the early days, and this was still in academia, called Photo PIPS, which stands for Photo Polymerization-Induced Phase Separation.


In most printable resinsyou print apart, it hardens, and it has a certain set of properties. To give it more properties, you have to put it in an oven and do other things to it. In this Photo PIPSprocess, as the resin is curing, it drives a change in miscibility in some of the cured parts and the uncured parts. It drives a force that has this homogenous material, that's kind of in one phase, start to separate in two phases. And so we get the resulting properties that look like a thermoplastic polyurethane or a thermoplastic elastomer but we get that out of a one part material that can all activate during printing. These two phases in these DuraChain resins separate to -70°C and then up above 100°C and we get very nice elastomeric performance across an almost 200°Ctemperature range. That lets us solve a lot of interesting problems as an industry that haven't been solved by traditional elastomers, let alone printed parts.

LG: So what were some of those problems that you were seeing in the industry?


WV: One of the automotive specs that's needed is survivability. In Alaska or Fargo, the temperatures can get down to negative 40°C and so a lot of automotive parts will get unbridled at that temperature, they'll squeak, they'll make noise, they'll fail unexpectedly. Having our low Tgphase down to -70 gives us a really nice buffer for ultra good elastomeric performance at low temperatures. Moreover, having this high Tgphase upat 120 to 125°C gives us thermal stability to meet most of the applications in cars, oil wells and planes, consumer products and medical devices. There's some specific under the hood applications and some space applications where we need even higher temperatures and we're not quite there yet.

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FreeFoam 3D printed car seat before and after heat treatment





FreeFoam iskind of the next evolution of these DuraChain resins and not only do we get all the properties of these phase separated materials, but we can print them sall, and then in a 60 second process in an oven, we can volumetrically expand them 2x to 7x. These all are working on the Xtreme 8Kwhich is the world's largest top down DLP printerby ETEC and what's really neat is the ETECprinter used to cost us, let's say 30 cents on the dollar for a part. so you look at the cost of the 8K, you look at the size of parts you want to make. Let's say we're making automotive seat cushions. We look at the number of parts you can make per year, and then you depreciate that over five years or three years or seven years, depending on what kind of business you are. There's been a cost per part that's associated with a tool and in most of the 3Dindustry, that cost per part based on the tool ranges from 30%maybe up to 70%. If we look at injection moulding, blow moulding, some of the world's great thermoplastic processing technologies, the cost per part that comes from the tool is pennies on the dollar,maybe two to 15 cents, or15%.What FreeFoamallows us to do is get into these margin regimes, where we can cost effectively make parts that before were only limited to injection moulding and we can print small parts in our more expensive tool, and then rapidly thermally process them and in an inexpensive oven to get these properties

LG: And from what I can see, you can really pack them in, and these are some very large final parts ...


WV: Absolutely. It gives us this ability to do ultra high throughput of printing small parts. But then moreover, for shipping, let's say we're making car seat cushions over in Asia, and we want to ship them down to Mexico for assembly, you'll pay a lot per space in a container, a lot more per volume than per weight. It's just how the global shipping industry works. We can take some of these FreeFoam specimens, even before foaming, we can heat them up and compress them and store them in a temporary shape. So we could be shipping something the size of a college textbook, and it could go through an oven and blow up into something the size of a king size mattress. So if we look at gummed up supply chains, ships being stuck in harbours not delivering goods, the ability to deliver a greater volume of goods more effectively, and then dopoint of use foaming, because that's a very simple process, there's no chemicals, it's basically running it through a pizza oven.

LG: You've spoken about the car seat example and I can see someapplication exampleshere in footwear. Can you share any other application areasthese DuraChain resins fit into?


WV: The DuraChain materials broadly address problems in several different market segments, transportation and automotive, consumer products, heavy industry, and then several others. For footwear and for wearables, Elastic Tough Tubber (ETR) 90, which is part of the DuraChain family, has passed the specs for biocompatibility.

We work with customers and do a lot of application specific testing. So whereas a lot of the 3Dprinting world will test the quasi static properties of materials - so you compress them once and see when they break or pull them once and see when they break - We beat up these elastomers over hundreds of thousandsof cycles and then study creep, fatigue, wear, compression, fixity, and then engineer the parts subject to the

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Inside 3D printed FreeFoam car seat cushion





loadtensors that our partners need so that we can use mass in the most efficient ways. A lot of 3D printing uses simple tessellated lattices, you take a Body-Centred Cubic (BCC) structure, and then you tessellate that across your part, and it's pretty good, and it's pretty strong. But it's pretty good and strong against forces in all directions - most end products are used in a very specific way. An automotive seat, if you think about how you get in a car, that outer lip takes a lot of force because when you get in a car, you sit down on it, you twist the feet around and so that outer lip needs to really be strengthened. But if the other part of the foam had to be hardened against the same forces, you'd be wasting a lot of mass. And so we're able to work with with some of the world's greatest companies that know exactly how consumers engage with our products and we can help them build their products subject to those needs, that uses much less material than conventional technologies. That leads to a lower cost of goods, that leads to a greener cleaner, more sustainable ecosystem and ultimately better margins for us. We can sell less material to solve a greater problem, and there's margin within the whole supply chain. All of the service providers that make that happen can benefit.

LG: Adaptive3D is now part of Desktop Metal. How is thathelping to accelerate this technology?


WV: DM has been an incredible fit, there's a great cultural fit. They spun out of the material science department at MIT, we came out of the material science department at UT Dallas and then I had my PhD from Georgia Tech where the company actually started. But we have this kind of material centric view of the world, that you can use science to come up with a better solution. And I think there are a lot of companies that need to make money and need to make money immediately and today, and are taking the best they can and really pushing hard the marketing and the prototyping. I think where DM has really built a culture and a team that is world's best is by going and identifying the marquee technologies that lead to area wide manufacturing, that will dominate by the end of the decade. We've had a very patient investor base, and a very great group of technologists that are helping make those technologies a realityso while we do a lot today to service prototyping and small scale processing, we have our eyes on the prize of fundamentally transforming how the world delivers goods and services to customers and a lot of what we're investing indoingis getting us closer to that by leaps and bounds every quarter. So it's really exciting to be a part of that ecosystem as an entrepreneur.

LG: This last question is a bit buzzwordy but the way you speak about the transformative process of FreeFoam, it'ssimilar to how I've heard other people define '4D printing'. Would you ever use that terminology for this?


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FreeFoam close up showing variable lattice densities





WV: I will defer that to our marketing team!But I will leave you with a quote from a good friend from a big shoe company who will remain unnamed but they don't like to say parts are 3Dprinted.They want to have a product that delivers superior performance to athletes and they brand it with the best athletes in the world, and are almost agnostic to that technology. In some sense, there is a lot of buzz and hype riding behind 3Dprinting but our goal is to really deliver value to our end customers by solving hard problems in more elegant technical ways. And FreeFoam does that in the scalable polymer chemistry route, a lot like the P50 does on high throughput metal printing, and Forust does that in wood printing, and the S Max Flex does that in big sand casting. So in each of those cases, we found the key problems in the market that have limited technology from achieving mass adoption, and spent a lot of money and a lot of time and a lot of PhDs, beating their heads against walls, coming up with a way to solve that. So it's really exciting to be a part of that process and that journey.


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