Some of the materials used in 3D printing are generally either not very, or even not degradable in the environment. Some developers and manufacturers though, are working to develop materials that are more eco-friendly, as well as delivering the mechanical properties designers look for. Here is an interview with Dr. Raymond Weitekamp, founder of the Berkeley-based 3D printing startup, polySpectra. We spoke about a new material being used to create engineering grade parts through 3D printing, and how it can help shrink the carbon footprint.

 

 

MPF: What is your new material, COR Alpha?

RW: COR is the acronym for a new family of photopolymers that we invented at polySpectra and it stands for, Cyclic Olefin Resin. COR Alpha is the first one of those materials. We also have a material called COR Black, which is similar, but black.

COR Alpha is sort of the more interesting one in terms of bringing new capabilities. The fundamental chemistry of what’s going on in our Cyclic Olefin Resins is based on a reaction called olefin metathesis. And the catalyst inside, the chemistry is based on something that my PhD advisor, Bob Grubbs, won the Nobel Prize for in 2005. I didn’t invent anything related to his Nobel Prize. What I invented, when I was a graduate student at Caltech working for him, was a version of what people call the Grubbs Catalyst. So [this material] is a version of this Nobel Prize winning catalyst that would only be activated when you shine light on it.

From a chemistry perspective, what this offers the field of stereolithography, photopolymerization, or resin printing, whatever you want to call it, is actually a completely new chemical mechanism and manifold for that type of printing. And so, this is in contrast with the two main mechanisms over the 40 years since Chuck Hull invented stereolithography in 1983, or a photo radical system, or a photo acid catalyst system. And this offers a third mechanism that has a number of benefits on the chemistry side. The main value proposition, in terms of how this would impact designers and engineers, is really around being able to access incredibly rugged materials that have very high working temperatures, very high toughness, very high chemical resistance and weatherability and durability.

COR Alpha was the very first one, and the first in a long product line that we have. From the outside, looking in, the printer looks just like any other printer. And at polySpectra, we don’t make the printer, we partner with the hardware partners. Chemically what’s going on, on the inside, is completely different than what’s happening in a traditional resin and that enables us to achieve properties that have been elusive for the field of stereolithography for the last 40 years.

MPF: What would you say are the best applications for this material, given its high heat ability, its high strength capability, those other factors?

RW: There are a number of things that we’re working on. I guess the thing that ties them all together is… the best applications tend to be ones with the harshest use requirements. So they are all some kind of industrial additive manufacturing application.

MPF: Like, automotive? Aerospace?

RW: Automotive, aerospace, and both the commercial aerospace, as well as defense aerospace, and also both actual outer space and lower earth orbit applications.

We’ve been qualifying, as well, commercial aero components. We’ve been doing a lot in electronics, and connectors, and enclosures for… some of those would end up in cars and airplanes, but consumer electronics devices as well. Robotics and automation have been another really important application area for us.

We’re not very useful for stuff where SLA printing is sort of already good enough. If you just want a nice prototype that is going to sit on a shelf, or you’re just going to kind of test something and then throw it away, and you don’t care about the properties. I would say we’re much more interested in, and the places that we can really help people, are in additive manufacturing, not necessarily 3D printing, if that makes sense.

I’d say direct end use components is most of where we’ve spent our effort, although there’s a big market in what people call rapid tooling, and actually, a very large fraction of the polySpectra customer base is using COR Alpha for some form of rapid tooling. So, making mold inserts, for example, for injection molding or blow molding, so rapid tooling is an important one as well. But I’m personally passionate about the direct production of end use parts where, in one step, you can make what you want, in the shape that you want it, with properties that will be durable enough to be safe for end use, consumer grade product, all kind of in one step.

 

MPF: One of the issues with a lot of photopolymers is that either they degrade or yellow over time. Do you stop that light interaction process?

RW: It is a tricky thing with photopolymers, and it’s tricky for everyone, regardless of the mechanism, in part, because you’re using light to cure them in the first place. So a lot of the things that you would do to, let’s say, with a thermoplastic where you’d fill it with black pigment and UV blockers, you can’t really attenuate all the light in a photopolymer, because you want to use the light to trigger the polymerization. So there are aspects of that degradation that are, I would say, universal, it doesn’t really matter which resin chemistry you’re doing. I would say that we are definitely better than the average resin in that regard. And part of it is that we’re starting from really amazing properties. So we start from very, very high tensile strength and ductal failure and really high working temperature and almost no moisture absorption, which can play a role in degradation. So, some of these degradation processes are catalyzed by light and oxygen and moisture. If you have really low moisture diffusion that can help.

I would say, we’re better than the average here in terms of the UV degradation. And then, actually, we’ve also come up with some really creative solutions where we’ve partnered with various coatings companies to just completely eliminate this entirely.

One of the more recent ones that’s exciting is with a company called Cerakote, and we did this fun partnership after meeting them at RAPID a little under a year ago, where we saw that they have this rugged coating. And they said, “Well, hey, we have the most rugged coating, you have the most rugged material, let’s combine these things together.”

We started with one of the product lines of theirs that was the best at UV mitigation. We coated it with this Black C Series Cerakote Spray Coating, and even though it’s a spray paint, it’s very thin. It doesn’t actually change the dimensions of the part much. And then we put it in a QUV chamber, which is like a hot and humid weathering chamber and nothing happened to it. And we ran it for, I think the first time point was a thousand hours, which was kind of their first initial checkpoint, and nothing happened to it. So, they just put it back in and it’s still been running. We’re just going to keep running until something bad happens. Maybe a coating might not be the best solution for every application, but that’s one where we’ve combined this sort of best-in-class coating system with a partner with our best-in-class thermo mechanical base material to unlock super durable components.

MPF: What kind of a carbon footprint does it have?

RW: So that’s a good question. I’ve spent a lot of time working at the intersection of sustainability and additive manufacturing. There are a number of different components to calculate the total life cycle energy of [the material]. One of the most important ones, when you’re thinking about 3D printing versus, let’s say, injection molding, would be the process energy.

And that is, what is the energy that is being used to set the shape of the material? In a molding press, that would be the energy of keeping the mold hot and bringing the heavy press together with pneumatic power and high heat. We mostly do DLP printers, so in that category of stereolithography, the energy would include the electricity draw of the printer. In the specific study that we did, where we were benchmarking this, (see references).

The process energy, to be fair, if you’re going to do molding versus printing, then you have to include whatever the post process might be. For COR Alpha, after you print the parts, we bake the parts in an oven for about two hours, to get to the high working temperature of COR Alpha where the glass transition of this material is about 170 C. That’s necessary by definition.

So the process energy for the COR Alpha would be the power draw of the printer, plus the oven, versus the injection molding press. What we measured, based on studying this, …., was that printing COR Alpha, the total process energy is between 50 and a hundred times lower than an injection molding press. Even with the oven, because …. once you get the oven up to temperature, it’s not a big deal.
Whereas, in the molding press, … they weigh a lot and they have to stay very hot and have pneumatic pistons to drive them. So, there’s really a lot of process energy there. So, basically, printing our stuff, in this case, the printer that we benchmarked, it was an Origin printer, which is now part of Stratasys. That was between one and 2% of an injection molding press, so 50 to a hundred times more energy efficient.

If you think about a typical injection mold part, I had the fun opportunity to explain this to Bill Gates once and I was showing him some Legos, which are ABS plastic, I said, “Okay, Bill, a third of the carbon footprint of this Lego brick came from that step where you had to mold it into the shape of the Lego. Right?” In terms of that perspective, you could save, …. you could basically eliminate a third of the total carbon footprint of this polymer product by switching from molding to printing.

Where it gets a little bit more complicated is now you have to start to think about what’s called the embodied energy of the material. So here’s where you say, “Okay, well, what’s the equivalent kilograms of CO2 emitted, per kilogram of plastic? Or polymer?

Something like polyethylene or polypropylene, which is milk jugs, plastic bags, things like that. Those are actually incredibly efficient. They have very low carbon footprint, because the ethylene and propylene are sort free when you’re on your way to drill for oil.

Compared to polyethylene or polypropylene, the total embodied energy of COR Alpha is quite higher… quite a bit higher, but compared to more engineering plastics, like ABS or Delrin or Peek, you’re talking 7, 8, 9, 10 kilograms of CO2 equivalents created in the process of making those polymers. … The bottom line, the sort of takeaway is, depending exactly on what polymer you’re comparing to, we can save between a third of the total embodied energy of that polymer component to two thirds. So between, let’s say, 30 and 65% depending on what you’re benchmarking to. And so that’s actually really huge. And just in the US, if this were widely adopted, that could be a few percent of all US energy, if you were starting to switch to something like our process versus injection molding.

And the even bigger carbon footprint opportunity in an initiative I’ve been working on that we call Massless, which is the mission to use digital manufacturing to reduce global energy usage by 25% by 2050. …. This idea of Massless and the Massless mission is, if you could build a part locally, or even if you could just do it on the same continent as the end user, that’s where you could start to save double digits of global energy usage.

Because the other thing that most people don’t appreciate is that the components in your iPhone flew halfway around the world, four or five times before it was fully assembled, then they went to the warehouse, then they went to you. So the environmental footprint of moving mass around the world is massive. And, in the US, about 30% of all US energy goes to transportation fuel, of just moving stuff around.

So that’s where people call this the virtual warehouse or distributed digital manufacturing. … It’s going to take the longest to get there, because it really involves a total behavioral change on the part of the whole supply chain of the earth. But the impact is insane. And the scale of the energy savings are really massive.

MPF: What happens when the product reaches the end of its life cycle? Is this material easily degradable?

RW: Right now, we’re mostly focused on use cases where you want the best way to optimize for the total embodied energy and carbon footprint is to make something last forever. There tends to be a trade-off between making something easily recyclable or biodegradable and also making it the strongest, toughest material of all time. We are… mostly focused on the durability aspect of it and saving energy on, let’s say, the front end of things, rather than through more of a circular approach, but we are working out a number of different end-of-life strategies with some of our partners and suppliers who have been making similar kinds of materials for years. We have a few collaborations, much more on the kind of R&D side of things where we’re thinking about ways that you might be able to recycle or give a second life to the material. But that is tricky.

We’re also not interested in doing anything that is consumable. …. I think there’s a lot of people who think, because a huge portion of the plastics that we have on the planet are thermoplastics and can be recycled, they think many plastics must be sustainable.” And that can be true, if it actually is being recycled. I certainly think that there are tons of amazing applications where we need a circular economy approach to things. And I’m friends with a lot of pioneers in that field. People have worked their whole careers in polymer recycling, like Mike Biddle, and it’s really important. At the same time, it doesn’t solve everything.

And there are also lots of kinds of polymers that are not easily recyclable because of the chemistry. … So it’s not black and white, “Oh, it’s recyclable. It must be eco.” “It’s not, it must be terrible.” There’s actually really a lot of nuance and it can be incredibly complex.

MPF: Let’s switch over a little bit to the design side of things. Given the characteristics of this material, are there any specific challenges in designing with it that a mechanical or an electrical engineer needs to ponder?

RW: I would say we’ve worked really hard to fit our design requirements within the realm of what would be normal design for DLP, in general. You might want a slightly different support strategy with our material than with a really brittle acrylate, where you might … more of a lattice type support structure, I would say. We’re definitely within the normal design roles of what people are used to in DLP, or this kind of like upside down SLA printing, which is a little bit more restrictive than a top down system, but then you kind of have different benefits on the materials that are available.
I would say the one thing that is a little bit challenging in terms of design is … if people want to do really super thin, super tall structures with our material because it hasn’t reached its full strength out of the printer; it gets its full strength in the oven. It’s not usually something that gets in the way of us engaging with customers who are familiar with DLP printing or SLA printing. But that might be one of the drawbacks versus standard acrylate ….

MPF: I think that’s just a consideration given the fact that the material gets its hardness once it’s been baked. So, that’s the factor you kind of have to keep in mind is, whatever you’re designing, recognize that there’s this additional step that’s going to finally deliver the strength that you are looking for.

RW: Exactly. We work really hard to build a process where it goes through both of those steps and maintains a really high accuracy. If you’re really thin, it makes it tricky to do that, because you’re so susceptible to any kind of deviation.

MPF: Does the materials shrink at all during baking, like metals do?

RW: No, actually. It was not planned on our part, but it turned out to be remarkably valuable when comparing to photo radical resins—we have almost no volumetric shrinkage in our process. Some of that just comes from the nature of the polymerization mechanism, which is called ring opening with metastasis polymerization.

One of the fundamental limiting factors to accuracy in stereolithography broadly, is the shrinkage of the photo polymer. … There is kind of a fundamental floor called random noise shrinkage. … As we started to get more involved in this space, we discovered that this really low shrinkage was enabling us to print parts with much better dimensional stability than a traditional acrylate resin.

We came up with a new product that we’re starting to roll out now called COR Cure for people who have a normal oven where we can protect the part and just bake it….

We’re definitely not in a form factor to have people print in their home or print in their office. It needs PPE and chemical safety protocols. It’s much more like a serious engineering resin. But again, most of the customers that we’re focused with are at the cutting edge of additive manufacturing and doing these things in their factories or kind of R&D centers. I guess I would say we’re trying to make it accessible. It’s not quite ready for people to print in their garage with, but we’re working towards that.
The three printers that we run on, that we’ve publicly announced are all the printers from Asiga, which are all DLP 385 Nanometer DLP systems. About a month ago, we announced with Stratasys for the Origin One at RAPID …. And then there’s one printer from EnvisionTEC, that’s now called ETEC, that we support called the E-One. There are more coming down the pipeline.

I’m really excited about with additive manufacturing is, I finally feel like this is a true ecosystem. … Now there’s really an open marketplace, there’s an open ecosystem. … People are jumping into different kind of niches that I just find so fun and invigorating. And, whether it’s a service bureau that prints parts and also specializes in a niche application area, or companies that have some software thing, … I feel like there’s a much more healthy ecosystem to this space now. … It’s more collaborative.

 

References:

The Future is Massless:  https://massless.dev/  

Why 3D Printing Is a Critical Part of the Battle Against Climate Change:  https://medium.com/polyspectra-wavefront/why-3d-printing-is-a-critical-part-of-the-battle-against-climate-change-726e493a3f58

DOE Awards $57.9 Million to Reduce Industrial Emissions and Manufacture Clean Energy Technologies:  https://www.energy.gov/eere/amo/articles/doe-awards-579-million-reduce-industrial-emissions-and-manufacture-clean-energy