The State of Resin 3D Printing: David Walker, Co-Founder Azul 3D & Northwestern University researcher

Recently, 3D Printing Industry launched our spotlight on resin 3D printing survey to better understand how this fundamental additive manufacturing technology is used.

We’re also speaking to experts about how vat photopolymerization has matured over the years and the future opportunities for resin 3D printing, whether via advanced materials development or underdeveloped commercial opportunities.

David Walker is the Co-Founder of Azul 3D and also a Northwestern University researcher. At Northwestern Walker conducts research in the areas of nano-scale printing/lithography tools and disruptive large-scale additive manufacturing capabilities. He is also a board member with RadTech, a non-profit association for UV+EB photopolymer chemistry.

Our survey is still open, please follow the link to tell us about your experience with resin 3D printing. We’re not collecting emails (unless you want to provide one), so feel free to tell us about the reality of working with resin.

A LAKE printer factory. Photo via Azul 3D.
A factory of Azul 3D LAKE 3D printers. Image via Azul 3D.

3DPI: How have you seen resin-based 3D printing develop in recent years?

David Walker: I think there has been a major refocusing on ultimate material properties. Carbon is primarily responsible for giving the industry a kick in the caboose back in 2016 and 2017 on this front. They started to property-shame key market leaders with their innovative approaches and two-part resins. And while many end-users have found the two-part resins a bit of a hassle to use, they have spurred on a great amount of innovation in the field. UV-curable resins are no longer just considered brittle glasses. Resin-based 3D printing used to be considered the worst with regards to material properties in the plastics space – now it’s considered the best and most versatile platform…it’s infinitely tunable. 

The other big trend has been suppliers increasing the viscosity of their resins using high-molecular-weight polymers to get a boost in material properties quickly. This was fine to address the immediate market need, but it really didn’t require a lot of detailed chemical understanding or insight to achieve. The big challenge in the field today is that these higher viscosity materials ultimately become problematic and rate-limiting to printer operation speeds. At present, development in the field is striving to keep these great material properties but to develop one-part resins that are low viscosity to get the job done quickly.

3DPI: What do you consider the next technology hurdles for photopolymer-based 3D printing to overcome?

David Walker: Like I said above, getting great material properties of lower viscosities is a big challenge. The other big things going on pertain to what I would consider ‘secondary’ properties. Everyone looks at tensile and elongation… but if you sacrificed on a secondary property such as water adsorption, then your cheap tough-resin might actually be useless to an end consumer. No one wants a plastic part that swells 5-10% when it’s in a humid environment. Now a good resin is achieving high marks on both the classical ‘primary’ mechanical properties, but it also has to address all the other ‘secondary’ properties that a customer might not consider or declare to you up front. 

Lastly there seems to be challenges with supply chain sourcing and consistency. There doesn’t seem to be a great or universally agreed upon method for testing resins. So printer-to-printer and resin bottle to resin bottle there are variations and as a result the end user can get very wildly different material outcomes. Right now the field is very much based around ‘tuning a machine in with a resin’ because both the machine and the resin are changing over time. The consistency problem will be big for end-user adoption.

3DPI: What applications of vat photopolymerization do you see as under-developed by the market, and why?

David Walker: Right now there seems to be a lot of interest in getting material properties that can increase the total addressable market; everyone is searching for new customers wanting to adopt AM at scale and find the best use-cases. For example, right now there’s been a big push where every company is announcing their work on a UL flame-resistant resin. If a company hasn’t pushed a press release yet, it’s probably being worked on in the back of house. 

This is an important property for many commercial end-users where regulations tightly dictate the flamability ratings of the plastics used. This isn’t just aerospace or defense contracting either – it’s in a lot of consumer-focused goods. Just think of how many times you see that little UL logo hiding in a day!

3DPI: Where are opportunities for materials development in regards to vat photopolymerization technology?

David Walker: Tear resistance in elastomers with good rebound. Many of the classic polymer-physics tricks used in molded parts can’t be used in 3D printing because of the requirements on fluid flow. Filled resins can certainly enhance these properties, but they are tricky to print with. Just like the Tethon resins – when they work they are amazing…but when there is an issue they are a thick, slurry mess. 

This is the inherent challenge in loading a resin with particles of any nature – ceramic or otherwise. On the tough/durable front – there is a lack of a good high-temp and high-elongation plastic with good impact properties. People have struggled to get really high heat-deflection temperatures – which are important if you are ever shipping a part in the back of a semi trailer or on a container ship – without making major sacrifices in overall toughness.

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Featured image shows Sisma Resin 3D printing. Photo by Michael Petch.