3D Printing ProcessesMaterialsThermosets

Exclusive: a new era of polyurethane 3D printing

Chromatic 3D Materials is tuning chemistry instead of mechanics

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While covering the global additive manufacturing industry, we occasionally run into startup companies working on technologies that may seem marginal but have a huge potential. It’s not just about having a good idea, as much as about finding true manufacturing pain points—which is not nearly as easy as it sounds—and, more importantly, having the know-how to address them. Chromatic 3D Materials‘ work with extrusion of thermosets, polyurethanes in particular, is a perfect example. The ability to proficiently, and cost-effectively, 3D print one of the world’s most used materials will open an enormous opportunity. And one of the best parts of C3DM’s approach is that this opportunity could be exploited by every one of the many extrusion 3D printer manufacturers around the world.

The company’s approach is materials- and software-based, and hardware agnostic. Chromatic 3D Materials’ FlexTune™ 3D Printed Polyurethanes are a range of rubber elastomers that offer both high-performance and high flexibility, with almost endless potential applications, from automotive to consumer products. CEO Cora Leibig founded the company back in 2016, building on a 20-year career in the materials industry. At Dow Chemical she worked in corporate R&D and polyurethanes-specific R&D for a decade.

“For a new technology to launch in the materials world, you have to show that there are hundreds of millions of pounds of potential, Dr. Leibig explains, “and the reason for that is that the supply chain is so deep. There are so many steps you have to go through before you get to a final product”.

This is why she was initially drawn to 3D printing: “What interested me,” she explains, “is that you’re really taking material selection much closer to the end-users and this really changes the dynamics of what it takes to deliver innovative materials to the market. I think what 3D printing is going to bring to the world is innovative materials that we have not seen before and that have much higher functionality.”

Where are the thermosets?

Looking more closely at what materials were available for 3D printing, Cora Leibig noticed that the palette was really restricted for 3D printing. And— perhaps unsurprisingly— the biggest segment that was (and still is) missing is thermosets, a category that includes polyurethanes as well as silicones and epoxies.

This is due to the inherent characteristics of thermoset materials, which are at the same time very useful and also very difficult to 3D print. But difficult does not mean impossible. As in any manufacturing segment, it takes research. The biggest challenge for 3D printing polyurethanes, as for any thermoset application or process, is that the chemistry defines how it processes, more than the processing system’s mechanics.

In a thermoplastic filament printer, you have to tune the temperature of the printhead and the temperature of the bed. In thermosets, you have to tune the chemistry.

In a thermoplastic filament printer, you have to tune the temperature of the printhead and the temperature of the bed. In thermosets, you have to tune the chemistry. “In a thermoplastic filament printer, you have to tune the temperature of the printhead and the temperature of the bed,” Dr. Leibig explains. “In thermosets, you have to tune the chemistry. And it’s a little more complicated. At Chromatic 3D Materials we modify aspects such as the density of reaction types for the extruded materials, or how they mix together.”

The FlexTune™ range of polyurethane rubber elastomers are printed in the Shore A range of 40-90. These materials have been used for decades in non-3D printing applications that demand durability. They can be flexed, stretched, twisted, squeezed over and over. Examples of their use include heels and outsoles of shoes, rollerblade wheels and gaskets in hydraulic seals. The team at Chromatic 3D Materials found a way to 3D print using these high-performance polyurethane elastomers in a way that doesn’t sacrifice their strength and durability.

Chemistry vs. mechanics

The specific 3D printing process implemented by Chromatic can be described as a cross between ink jetting and extrusion. During the printing process, two liquid components are mixed in the printhead.  The act of mixing triggers a chemical reaction. By the time the liquid leaves the printhead and is deposited on the printing surface, the material is a partially-polymerized gel.  It solidifies to a stable tacky material within minutes. The entire process is carried out at room temperature.

In other words, whereas in thermoplastic extrusion, the material is melted and reformed, a thermoset material is actually being “created” during the extrusion process. This results in strong chemical bonds throughout the part, with more isotropic properties. “That means that in essence, that part that you’ve made is a single molecule,” Leibig explains. “The other advantage,” she continues, “is the way we design it: the material coming out of the tip is about ten thousand times lower in viscosity than a filament, which means you can print a lot faster.”

In essence, that part that you’ve printed is a single molecule

It’s much more of a chemistry challenge than a mechanical challenge, but this doesn’t mean that it’s insurmountable. And the advantage is that you can use all the tools that people have been using for thermoset chemistry for over 50 years and apply them to 3D printing. Leibig argues that the main reason why there has not been more progress is that it’s just that only a small number of people are researching thermoset 3D printing today.

One of these companies is Carbon, whose stereolithography-based digital light synthesis uses a mix of thermosets and photopolymers to trigger a photocuring process. Cora explains that Chromatics’ extrusion-based process offers much more versatility. “We’re just using the mixing to trigger the reaction. This allows us to go to a very flexible regime and also to incorporate additives, such as colorants,” she explains.

The Chromatic extrusion systems can be installed on any extrusion 3D printer, changing the thermal printhead with a thermoset one. Internally the team at Chromatic uses a standard, large format Juggerbot 3D printer. Chromatic provides the materials as well as the necessary software (more on this later). For many hardware manufacturers, the Chromatic 3D Materials system can represent a unique opportunity to significantly extend their market reach.

Looking for pain-point parts

Leveraging this versatility, Chromatic is focusing on applications such as seals and gaskets for industrial equipment, which are parts that have extremely high supply chain costs. A part that only requires a few cents worth of materials can end up costing tens of dollars because of logistics-related costs.

“When we look at the supply chain for seals and gaskets, there’s a lot of specialized equipment that might only need less than five hundred parts in a whole year. That’s for a given shape. For injection molding, this is just ridiculous economics,” Dr. Leibig explains. “So the logistics costs associated with these kinds of spare parts amounts to as much as 90% of the part’s cost and is mainly related to warehousing and distribution. Injection molders working on millions of parts a year don’t want to have to interrupt production to set up a five hundred part run.”

The logical deduction that Leibig and her team made is that these parts would be ideal for 3D printing if the materials could be good enough. “That’s really where we focus as a business – she reveals – and we’re finding a lot of success with small fleets, whether buses or trains or tractors or classic cars or even just machinery in factories.”

Because the FlexTune™ materials solidify during the build process, and don’t require heating to avoid deformation, part heights of 20 cm and above can be obtained. The main limit is that defects propagate during the build so Chromatic has developed an AI technology to compensate for any defects that arise, which means that about 50% of the R&D time is dedicated to software development.

In terms of speed, FlexTune™ materials can be printed about five times faster than in thermoplastic extrusion processes. “We do see opportunities to go even faster, as much as another five times faster, through equipment upgrades,” Leibig explains. “Another major feature is that our parts are one hundred percent solid, which gives us several advantages in parts where you have to seal to maintain pressure.”

Another major feature that Chromatic’s customers seem to appreciate is that the technology can be used to print on top of other parts. This means eventually using a five-axis robot, for example, to print on metal parts. “We see a lot of opportunity for metal parts that need integrated cushioning or sealing,” Leibig says.

Thermoset 3D printing services

Chromatic 3D materials operates today as a specialized service provider and consultancy. “Many of our customers don’t want to be involved in the printing process – Leibig explains. “Our business model involves targeting OEMs that maintain very large spare parts libraries. They’re trying to maintain physical libraries that include five hundred or more different elastomeric parts.”

For example Deutsche Bahn, the German rail service. With trains that have as many as 50 years of operation, many spare parts are no longer available. “We worked with them to look at their library and identify parts that could be 3D printed with our technology. Then we went through a program for qualifying the parts. Our ability to rapidly modify material chemistry enables us to easily meet any specific part requirements.

To date, Chromatic has built a library of 500 materials based on different chemistry variations. “In just about four weeks, we can usually develop a new printable material that can meet either thermal, mechanical strength or fuel resistance requirements. In that sense we also work as a consultancy service,” Cora explains.

Now the company is looking to expand the number of internal systems to service more clients with larger part batches. A key area for business development is to target spare parts suppliers, becoming a specialized thermoset 3D printing resource for small and medium size batches of hard to find parts. “Many times they don’t even have the CAD drawings for the part anymore and that’s why we believe it’s important that we maintain a chain of control around production, so that once they build what we call a ‘digital mold’ for their part in the library, we can guarantee a very short turnaround time.”

As demand grows, the ability to rapidly qualify parts for use is going to present a new challenge. Working with a company to qualify a new material for an application can take as much as six months but polyurethanes are already used in so many traditional manufacturing applications that in many cases they are already qualified by national and international organizations. That’s why the potential opportunity for 3D printing it is so significant.

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