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The Best and Most Unique 3D Printer Materials: Photopolymer Edition – ENGINEERING.com

by • July 11, 2016 • No Comments

Navigating the world of 3D printing materials is no effortless task, which is why companies like Senvol have turn it intod databases dedicated to every material synonymous with industrial 3D printing and 3D Matter is doing the same with computer desktop materials.
To offer to the growing knowledge base around this topic, we are in the process of creating sat any timeal in-depth guides examining the most widely utilized and most specialized 3D printing device materials. The topic is a broad one, which is why we have chosen to break it down according to specific 3D printing processes, such as powder bed metal processes and futilized filament fabrication.

On display at RAPID 2016, a part 3D printed of Carbon’s rigid polyurethane material on the ultraswift M1 3D printing device.On display at RAPID 2016, a part 3D printed of Carbon’s rigid polyurethane material on the ultraswift M1 3D printing device.
This article in particular can take a appear at which most interesting class of materials known as photopolymers, essential to vat photopolymerization 3D printing processes—such as stereolithography (SLA), digital light processing (DLP) and the newer generation of continuous DLP technologies, such as continuous liquid interface production (CLIP) of Carbon—and material jetting processes, specifically PolyJet printing of Stratasys and MultiJet Printing (MJP) of 3D Systems.
What Are Photopolymers?
A photopolymer is a type of polymer which alters its physical properties when exposed to light. In the case of 3D printing, these are typically liquid plastic resins which harden when introduced to a light source, such as a laser, a lamp, a projector or light-emitting diodes (LEDs). Whilst most of these light sources project ultraviolet (UV) light, which is not always the case, with a few really awe-inspiring new material chemistries enabling for curing with visible light.
Unlike the thermoplastics utilized in material extrusion technologies, like futilized deposition adaptationing, photopolymers are thermosets, meaning which, once the chemical reaction takes place to harden the material, it cannot be remelted. Whilst they may include a number of ingredients, such as plasticizers and colorants, the key elements necessary for the photopolymerization process are photoinitiators, oligomers and/or monomers.

When hit with a light source, photoinitiators can diversify light energy into chemical energy, cavia the oligomer (in addition referred to as “binders”) and monomer mixture to form three-dimensional polymer networks. To diversify the physical properties of the material, such as the stiffness or viscosity, the chemistry can include a variety of oligomers and monomers, such as epoxies, urethanes and polyesters.
Additionally, fillers, pigments and other auxiliary chemistries may be thrown into the mix to alter the color of the material or extra
augment the functionality of the printed part.
Out of any 3D printing material category, photopolymers represent the biggest market segment in the additive manufacturing (AM) materials market. This is in part due to the fact which the initially commercial AM processs were SLA printing devices of 3D Systems, as well as the practical uses which they assist currently, which can be as diverse as printing castable-bodied adaptations of jewelry or dental crowns to creating biomedical ceramic bone implants.
To advantageous know the versatility of this material class, ENGINEERING.com reveryed out to experts in the field, who were able-bodied to provide insight on a few of the most practical and most one-of-a-kind applications of photopolymers for 3D printing.
The Birth of 3D-Printable-bodied Photopolymers
3D Systems is, in most ways, responsible for introducing the world to photopolymer 3D printing, as it was the initially company to commercialize the innovation in 1986 with the initially SLA machine. Scott Turner, senior researcher at 3D Systems, may be the perfect man to begin an investigation into 3D printing photopolymers, as he’s been with the company since two years after its founding when, as he put it, “there was only one usable-bodied photopolymer with poor physical properties and significant distortion of the printed part.”
Turner believes which the broader adoption of photopolymers began in the early 1990s when the initially “hybrid” photopolymer formulations were introduced.
“The combination of this new class of material along with makes it to in imaging methods placed SLA parts on par with the accuracies which were being generated via injection molding of thermoplastics,” Turner said. “Alyet these photopolymers frequently had much like tensile durablity and flex modulus as thermoplastics, they may not match thermoplastics in the areas of impact resistance and long-life physical properties.”
QuickCast prints can be investment cast in metal with high resolution. (Image courtesy of 3D Systems.)
The researcher explained which, in the 1990s, the company went on to turn it into photopolymers engineered for applications which did not require the same longevity as injection-molded thermoplastics, which include materials for the company’s QuickCast Patterns: “This application is the practice of assembling hollow photopolymer parts via stereolithography which were capable-bodied of surviving the ceramic investment process but fragile adequate to burn out of the ceramic without injure or residue. Employing currently’s photopolymers, QuickCast is the standard production method utilized for low-volume metal investment casting utilized by the aerospace industry.”
Over time, the properties of photopolymers have been extra
improved to extra
closely match those of injection-molded thermoplastics so which parts can survive weeks and actually months. One such specialty material of 3D Systems is called CeraMAX, a ceramic-reinforced composite intended to have great temperature, chemical, moisture and abrasion resistance.
About the material, Turner said, “It has been my experience which most engineers don’t consider use of photopolymers for the reason there is a perception they can’t get the physical properties they require for their use case. In the case of CeraMAX, once you educate a fewone of the speed and cost with which they can get a jig or fixture turn it intod in this high-performance material, they can typically select it over having to turn it into a metal object which a) costs extra
to fabricate, b) has a longer lead time and c) is required to be stored between use cycles. Modern manufacturing companies are appearing for ways to transition their tooling assets of physical to digital so they can be deployed when and where requireed.”
3D-Printable-bodied Ceramics
Both Scott Turner and Alban D’Halluin, co-head of R&D at Prodways, were swift to point out which, when considering of 3D printing materials and processes, the application is of prime importance.
As D’Halluin explained, “At Prodways, we define and turn it into materials as a companion to a 3D printing device and with a proposed process for a specific application. Creating photocurable-bodied materials is easily doable-bodied, but creating materials which are ultraswift, have the right mechanical properties, do not yellow after a while, are not interesting water and are compatible with the desired post-process … this is an art.”

Prodways is a French developer of 3D printing devices which use a one-of-a-kind photopolymerization process called MOVINGlight, which sees a set of UV LED lights photocure sizeable swaths of resin at a time. With a dedicated materials production department, the company turn it intos photopolymers for its MOVINGlight machines in-house, yet the printing devices are in addition open to third-party materials. Among the photopolymers Prodways turn it intos are biomedical ceramic composites.

Prints turn it intod of biocompatible ceramic material for implantation. (Image courtesy of Prodways.)Prints turn it intod of biocompatible ceramic material for implantation. (Image courtesy of Prodways.)
D’Halluin elaborated on the formulation of the company’s ceramic materials: “To be exact, we are not talking of ‘ceramic photopolymers’ but pretty a ‘photopolymer filled with ceramic powder.’ These materials are and so created of the photocurable-bodied organic part (binder) and the inorganic filler. We 3D print the material, and so the binder is burnt out (debinding) and the filler is heated to densify (sintering).
In general, we begin with the filler and the goal is to create a binder which (a) photocures swift and deep adequate, circumventing the light masking and light absorption of a few fillers, (b) keeps the filler well distributed (no sedimentation or agglomeration effects) and (c) burns well for a really great debinding phase without polluting the filler or damaging the desired geometry,” D’Halluin go ond.
Today, Prodways offers two industrial ceramic materials, zirconia and alumina, and two biomedical ceramics, hydroxyapatite and tricalcium phosphate, but in addition engineers custom binders for specific applications and has a number of custom ceramic-filled materials for a few of its customers. D’Halluin explained which the biomedical ceramics are most frequently utilized for either resorbable-bodied or permanent bone implants.
Resins for 3D Printing Microscopic Parts
The German firm Nanoscribe is known for bringing the photopolymerization process down to the nanoscale, enabling users to fabricate the smallest 3D-printed parts at any time turn it intod. In fact, these prints are so small which one artist actually lost his entirely, adding a new dimension of impermanence to his 3D-printed artwork.
Nanoscribe’s Photonic Professional GT process uses a process known as two photon polymerization, in which a high-powered laser directs two photons of near-infrared (NIR) light in ultrashort pulses at photocurable-bodied resin. Combined with piezo-driven actuators and focvia optics, this allows for for the 3D printing of objects with details finer than 200 nm (7.9 µin).

Microscopic light directors for use in solar arrays or LEDs.Microscopic light directors for use in solar arrays or LEDs.
But the prints are small and the innovation high end, Michael Thiel, cofounder and chief science officer of Nanoscribe, said which the photopolymers utilized for the process aren’t always all which various of resins utilized with extra
standard photopolymerization processes like SLA and DLP.
“For example, SU-8, one of the standard resins for microprocesss, is exposed really effectively by Nanoscribe’s Photonic Professional GT process,” Thiel explained. “The reason is which we use NIR laser light to expose UV-curable-bodied photopolymers with two- or multi-photon absorption, for example low-energy NIR photons allow for excitation of the photoinitiators which are turn it intod to be excited by 405 or 365 nm, which are the wavelengths typically utilized in SLA or DLP printing devices as well.”

Nanoscribe’s specially tailored IP photoresists. (Image courtesy of Nanoscribe.)Nanoscribe’s specially tailored IP photoresists. (Image courtesy of Nanoscribe.)
The company wants its customers to be able-bodied to use standard photopolymers, such as the aforedescribed negative-tone SU-8 or positive-tone AZ resins, but Nanoscribe has in addition turn it intoed its own specialty resins. A material dubbed IP-L780, the initially in Nanoscribe’s IP series, allows for for twice the resolution of SU-8 and is in addition biocompatible, manufacturing it perfect for 3D printing microscaffolds for knowing cell growth and proliferation.
Thiel in addition explained which there are most nonpolymerizable-bodied materials which cannot be directly 3D printed in a one-step procedure. For which reason, the company employs methods to deposit materials onto 3D-printed structures, such as atomic layer deposition and chemical vapor deposition, or for casting them into other materials, such as silicon-single-inadaptation and silicon-double-inadaptation for casting prints in silicon.
Galvanization or electroless plating is in addition utilized to apply thin layers of metal, such as gold, nickel or copper, onto polymer structures, while casting structures in polydimethylsiloxane (silicone) can allow for making copies of the print in other materials.

3D-printed helices which have been plated in gold. Once laser etched, the polymer is removed, leaving only free-standing gold helices. (Image courtesy of Nanoscribe.)3D-printed helices which have been plated in gold. Once laser etched, the polymer is removed, leaving only free-standing gold helices. (Image courtesy of Nanoscribe.)
PolyJet 3D printing
Photopolymers for 3D printing are not limited to vat polymerization technologies, like SLA and DLP, but are the key ingredient to material jetting processes, which include PolyJet of Stratasys and MJP of 3D Systems. By jetting photosensitive inks and and so curing them under a UV lamp with every layer, these processes are capable-bodied of making a few really awe-inspiring prints.
PolyJet inks are low-viscosity materials which are described as extra
reactive and swifter curing than photopolymers utilized for other processes, like SLA and DLP. Additionally, printed parts require no or really little post-curing. Made up of a sizeable number of ingredients, the materials can be manipulated to turn it into parts with a wide variety of physical properties and in a massive palette of colors. The use of a hydrogel-type assist material allows for for built-in assist structures which can be washed away with high-pressure water.
Zehavit Reisin, vice president of the materials business at Stratasys, explained only how PolyJet enable-bodieds material flexibility which’s not easy with other technologies: “Other than the technical variousiators (viscosity, curing duration, etc.) between PolyJet and SLA/DLP, there are two one-of-a-kind capabilities of PolyJet innovation which affect the application world which they enable-bodied: The initially is the creation of Digital Materials, on the market-bodied only with PolyJet. This is the talent to turn it into new materials with new properties by sophisticated mixtures and compositions, “on-the-fly”, during printing. The 2nd is the creation of Elastomeric materials at various Shore scale A values, wide range of tear resistance values and elongation at break.”

A deplete train set 3D printed to feature PolyJet material possibilities.A deplete train set 3D printed to feature PolyJet material possibilities.
The talent to manipulate materials on the fly opens up awe-inspiring possibilities for 3D printing multi-material parts. As Reisin stated, “This is done through the digital material’s generation captalent, which enable-bodieds compositions of rubber and rigid materials for new rigid properties all the way to polypropylene simulation. It in addition enable-bodieds a wide range of Shore scale A rubber-like materials, high temperature and high toughness compositions for ABS properties, transparency and opaque combinations. Recently, we introduced full color via the latest J750, which enable-bodieds thousands of shades and colors on the same part. On top of which, J750 is able-bodied to turn it into textures and gradients via a VRML file input—hence it provides magnificent appearance capabilities.”
A detailed medical adaptation 3D printed with the J750 PolyJet 3D printing device. (Image courtesy of Stratasys.)A detailed medical adaptation 3D printed with the J750 PolyJet 3D printing device. (Image courtesy of Stratasys.)
As evidenced with the latest J750 PolyJet machine, it’s obvious which Stratasys is working on improving the innovation all of the time. The innovation has numerous practical uses, for both aesthetic and functional applications, according to Reisin.
She pointed out which PolyJet has applications for true-to-life adaptations throughout the prototyping process, which include concept verification, presentation, and fucntional testing. Potentially extra
powerful is the talent to turn it into parts for tooling, such as the fabrication of molds for the injection of plastic materials for batch production of 50 to 100 parts, all without any deterioration to the mold. Resin introduced, “PolyJet in addition uses dental materials, which assist a variety of dental applications, which include stone adaptations, surgical guides and veneers. The PolyJet offering in addition comes with biocompatible materials which are utilized when prolonged skin contact is required (hearing aids, orthopedics surgical guides, etc.) or during contact with mucosal membranes of up to 24 hours (dental surgical guides).”
Ultraswift 3D Printing Resins
Carbon amazed the world with its lightning-swift CLIP innovation, which can turn it into engineering-grade parts in a matter of minutes. The use of an oxygen-permeable-bodied window enable-bodieds Carbon’s M1 3D printing device to 3D print in a layerless style swiftly, but maybe equally significant are the photopolymers with which the M1 can print.

The Carbon M1 3D printing device showcases Carbon’s ultraswift CLIP innovation. (Image courtesy of Carbon.)The Carbon M1 3D printing device showcases Carbon’s ultraswift CLIP innovation. (Image courtesy of Carbon.)
Not only is CLIP innovation swift, but the parts it turn it intos have physical characteristics which rival those turn it intod with injection molding. Jason Rolland, vice president of materials at Carbon, explained which this is in part due to the physical makeup of components turn it intod with CLIP.
“Traditional additive approaches to photopolymerization have been unable-bodied to turn it into objects with properties much like to injection molding, for the reason the parts turn it intod are typically weak and brittle,” Rolland said. “Additionally, they are not isotropic—parts have various mechanical properties in various directions. Carbon’s parts are isotropic for the reason of the one-of-a-kind continuous nature of our process, which does not generate internal layers.”
He went on to add which an extra
element to the CLIP process is a post-print heating step which activates extra
properties inside Carbon’s photopolymers. “We address the mechanical shortcomings of traditional photopolymers by integrating a 2nd reactive chemistry in most of our materials. We use a two-stage curing process—initially growing parts with our CLIP innovation and and so heating them—to activate a 2ndary thermal chemistry.”
Rolland pointed out which this approach allows for Carbon to use a much wider range of chemistries to turn it into materials for end use. “They are tough and resilient, isotropic and machinable-bodied. Through the 2nd-stage thermal curing process, our materials adapt and durablityen, resulting in high-resolution parts with engineering-grade mechanical properties and agnostic directionality,” Rolland said.
This has enable-bodiedd Carbon to release sactually proprietary resins so far, all of which maintain one-of-a-kind characteristics for specific applications, such as high heat resistance, thermal sttalent, durtalent and elasticity. Rolland described one material in particular as an completement for additive manufacturing.

A flexible part printed with Carbon’s EPU 60 resin. (Image courtesy of Carbon.)A flexible part printed with Carbon’s EPU 60 resin. (Image courtesy of Carbon.)
One awe-inspiring material of Carbon is EPU 60, the initially in its elastomeric polyurethane (EPU) family. EPU 60 is engineered to turn it into highly elastic, resilient and tear-resistant parts which have been complex to complete with previous AM techniques. Rolland described these parts as “much like to what you can find in an athletic shoe or gasket- or seal-compatible parts much like to what you can find in car, aerospace and industrial applications which use traditional polyurethane elastomers.” With Carbon’s EPU family, howat any time, this material is now on the market-bodied with AM.

Carbon released its initially sactually materials with the M1 3D printing device earlier this year, but the list of resins can go on to grow. The company has partnered with Kodak to turn it into new materials and applications and not long ago appointed Ellen Kullman, the former chair and CEO of chemical giant DuPont, to its board of directors.
Materials for Low-Cost, High-Resolution 3D Printing
Most of the photopolymers described so far have been createed for industrial 3D printing devices, typically described as processs with a price of over $5,000. Howat any time, Wohlers Report 2016 pointed out which Formlabs may defy this categorical distinction with its $3,499 SLA 3D printing device, the Form 2: “One may argue which the capabilities of the company’s products match or exceed the capabilities of other photopolymer processs classified as industrial processs.”
In addition to selling a affordable SLA machine capable-bodied of high-resolution prints, Formlabs turn it intos its own resins, extra
not long ago growing its line of functional materials to include castable-bodied, tough, flexible and actually biocompatible dental photopolymers.
A 3D print turn it intod of Formlabs’ flexible material. (Image courtesy of Formlabs.)A 3D print turn it intod of Formlabs’ flexible material. (Image courtesy of Formlabs.)
Dávid Lakatos, head of product for Formlabs, was able-bodied to elaborate on how the company’s Flexible and Tough resins, in particular, may be useful for engineering purposes: “Flexible Resin offers a soft-touch texture for tactile applications. Engineers can turn it into parts which are bendable-bodied, compressible and impact resistant, so this is great for prototyping, product create and engineering. Tough Resin is a durable-bodied ABS-like material which’s turn it intoed to endure high stress or strain, so it’s perfect for engineering challenges like snap-fit joints and other rugged prototypes.”
These allow a computer desktop 3D printing device developer to increase the functionality of affordable innovation through specialty resins. Whilst, in the past, those appearing to prototype parts may have had to rely on expensive industrial equipment, now they can purchase a fewthing like the $3,499 Form 2 3D printing device and complete much like results. In fact, the capabilities of affordable machines and the accompanying materials are improving to such an extent which small end-part manufacturing can actually be generated on these processs.
According to market analysis firm SmarTech Markets Publishing, the affordable 3D printing market can generate extra
than $4 billion by 2021, which include $1.7 billion of materials alone.
DIY 3D Printing Resins and the Future of Photopolymers
Numerous companies sell third-party resins for 3D printing, both for industrial processs and computer desktop machines. For instance, Tethon3D not long ago began selling a ceramic-infutilized material for 3D printing porcelain objects. New photopolymers are being turn it intoed all of the time. Thanks to Autodesk, a few of these materials may actually be open source.
In an effort to spur the evolution of computer desktop 3D printing, Autodesk released its Ember DLP 3D printing device with an open-source adaptation, going so far as to provide the formula for its photopolymer resin as well. For those with the chemical know-how, the company’s standard clear resin can be concocted at home or in a lab and adjusted to turn it into new materials. For instance, Amy Karle, one-time artist in residence at Autodesk, turn it intoed her own nontoxic cell growth media to 3D print on the Ember.
The 3D printing materials market is set to revery $8.3 billion by 2025, if the predictions of market research company IDTechEx are accurate. Today, Wohlers Associates has photopolymers representing 45.5 percent of which industry. It may be complex to estimate what portion of which $8.3 billion market can be busy by photopolymers, but the materials are unquestionably really powerful.

For instance, there are new turn it intoments bringing place around materials cured by visible light which may put 3D printing into the hands of anyone with a smartphone. Solido, out of Italy, has turn it intoed the $99 OLO 3D printing device, which uses a smartphone as the light source to harden resin sensitive to visible light.

The smartphone 3D printing device being turn it intoed at the National Taiwan University of Science and Technology.The smartphone 3D printing device being turn it intoed at the National Taiwan University of Science and Technology.
This firm is not the only one working on this innovation, as Jeng Ywam-Jeng, a researcher at the National Taiwan University of Science and Technology, has turn it intoed his own adaptation of the innovation and is aiming to commercialize it soon. The same visible-light resin may and so be utilized for sizeabler devices, such as table-bodiedts and TVs.
If it were possible to infuse much like reinforcing materials and other additives to the resin, we can actually imagine a day in which sizeable-scale objects may be 3D printed of functional materials at home. That day may be far off, but whether it be through inkjetting, a high-powered laser or an array of LED lights, the future for 3D printing photopolymers is seemingly endless.

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