Welcome to this month’s last edition of 3D Printing News Briefs! Today, in honor a new month starting tomorrow, we’re starting with stories about everything new. BEEVERYCREATIVE will soon launch a new 3D printer kit, while Fast Radius is opening a new headquarters and Thor3D welcomes a new CEO. Verashape is introducing the latest version of its SOFTSHAPER software, and Link3D launched a new additive manufacturing scheduling solution. Moving on from new things, Midwest Engineered Systems, an official KUKA partner, will be displaying its technology at IMTS 2018, and a company used its innovative laser cladding technology to restore a CNC spindle.

BEEVERYCREATIVE’s New 3D Printer Kit

Portuguese 3D printer manufacturer BEEVERYCREATIVE is getting ready to launch a new 3D printer DIY kit, and will present it publicly for the first time at the upcoming TCT Show 2018 in Birmingham. This is a big deal for the company, as it hasn’t introduced had a product launch for a new 3D printer since 2015; employees have been very busy working on the MELT project for the European Space Agency for the last two years, and are more than ready to introduce the new B2X300 3D printer kit.

BEEVERYCREATIVE conduct multiple studies before the launch, including market research on 3D printer user patterns and collecting quantitative and qualitative information from users about its helloBEEprusa 3D printer kits. The B2X300 is named for the company’s brand (B), its two extruders (2X), and its 300 x 200 x 300 mm print area (300), and was delivered to several beta testers this spring for testing and feedback. Aside from its build area, number of extruders, and the fact that it features auto bed leveling and trinamic drivers, we don’t know much about the 3D printer kit yet. But all will be revealed by mid-September.

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Fast Radius Opening New Headquarters and AM Factory

The Fast Radius team, L-R: John Nanry, chief product officer; Bill King, chief scientist; Lou Rassey, CEO; and Pat McCusker, COO [Image: Manuel Martinez, Chicago Business]

3D printing solutions provider Fast Radius is scaling up its manufacturing footprint, and recently opened its new headquarters in Chicago’s West Loop, which features an advanced, industrial-grade 3D printing facility. This facility is home to extensive HP MultiJet Fusion technology, as well as what the company calls the largest Carbon production facility in the Western Hemisphere. This was a well-thought out location: the building of the Chicago-based Digital Manufacturing and Design Innovation Institute (DMDII) was where the company’s new CEO Lou Rassey first collaborated with several other Fast Radius executives, including Chief Scientist Bill King, PhD, Chief Product Officer John Nanry, and Enterprise Solutions Leader John Ramirez. The rest of the company’s executive team includes Vice President of Sales and Marketing Brian Simms and COO Pat McCusker.

Rassey said, “It was important to the Fast Radius team that we were headquartered in Chicago, as we are passionate about being a part of the next great industrial manufacturing renaissance in this city, the Midwest, and ultimately, the world.

“Pat, John, Bill, John and Brian form the perfect core team to grow Fast Radius as we build out our technology platform and global footprint to bring manufacturing innovation to the world at scale.”

Thor3D Welcomes New CEO

Anna Zevelyov

This week, Moscow-headquartered 3D scanner manufacturer Thor3D announced that it has appointed its very first Chief Executive Officer. The new CEO, Anna Zevelyov, is a company co-founder and a 3D printing market veteran who had been serving as Thor3D’s Sales Director; her long-time lieutenant, Vadim Fomichev, will now be taking on this role. Under Zevelyov’s leadership, the company will be focusing on R&D, with plans to release at least one new 3D scanner each year.

“Some history…the company was, until now, ruled by committee. Although periodically, this “collective-wisdom” approach was beneficial, over time we realized that a strict hierarchy and one person at the helm is needed,” Zevelyov wrote in a statement. “The Board of Directors took 6 months to consider whether to nominate a CEO and if yes, who that might be. After much debate about how this could change the culture of the company, the decision was made this month. I was elected unanimously, which, naturally, boosts confidence, as I take on this new challenge.

“I am honored and optimistic. My first priority will be R&D (after all, Thor3D is, first and foremost, a technology company). My aim will be to significantly improve our current technology and to introduce a new 3D scanner at least once a year (expect to hear big news before the end of the year). Another priority will be organization of our intellectual property. I anticipate filing a number of international patents over the next year to formalize the innovative work that has been done in the company over the previous months.”

New SOFTSHAPER Software Version

Verashape, which manufactures the VSHAPER line of 3D printers, has just introduced the latest version of its SOFTSHAPER software. Thanks to a license granted to the company by Siemens PLM Software last year, SOFTSHAPER 2019 is based on Parasolid Communicator. There are many improvements and new features in this latest version of SOFTSHAPER, including a technological process tree, detailed reports, and the ability to group layers and print manually adjusted supports.

“A huge simplification that SOFTSHAPER 2019 provides us with is the ability to print supports with higher density,” explained Seweryn Nitek, a Software Engineer at Verashape. “The density is higher only in the area of contact with the model. In other areas, the density of supports is selected in relation to the required stiffness. This saves time for printing supports, which are then removed by the user.”

Midwest Engineered Systems Displaying KUKA Technology at IMTS 2018

Two years ago at IMTS 2016 in Chicago, KUKA Robotics showcased how its robots integrate with 3D technology thanks to partnerships with companies like Midwest Engineered Systems (MWES), a leader in complex systems integration. MWES provides services such as robotic welding, machine tending, material handling, and automated production lines, but has become well-known in the last few years for its work in laser wire additive manufacturing. This technology is able to create very large parts, while also saving up to 90% of the material normally machined away.

“We’ve actually come up with a way way to print with metal using wire. Really what that does is allows you to print larger parts and it allows you to print them faster,” said Scott Woida, the President of MWES, in a video.

The company’s additive manufacturing system uses the hot wire process to preheat wire before it enters the molten pool. At the upcoming IMTS 2018, you can check out the MWES technology for yourself at KUKA’s Booth N-236200.

VIDEO

Restoring CNC Spindle with Laser Cladding

A company called Synergy Additive Manufacturing LLC (SAM), which claims to be one of the only turnkey jobshops to offer metalworking services like final machining, heat treating, metal forming, 3D CAD design, and 3D printing, also developed a laser cladding process is a more cost-effective alternative to hard chrome coatings. The company offers a 24 hour turnaround on the dimensional restoration of rotating components, like motor shafts and CNC spindles, using this technology.

In a new video, SAM demonstrated how its laser cladding method can be used to restore a CNC spindle. The technology offers a good metallurgical bond, and there is no chipping away or peeling once the restoration is complete. You can see this for yourself in the video below:

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Laser powder bed fusion 3D printing requires a great deal of effort to make sure that quality parts are being produced – and there are a lot of things that can go wrong with metal prints, such as porosity and residual stress, which causes distortion and part failure. Therefore, it is important to optimize the machine parameters as much as possible. In a paper entitled “3-Dimensional heat transfer modeling for laser powder-bed fusion additive manufacturing with volumetric heat sources based on varied thermal conductivity and absorptivity,” eight 3D heat sources used for simulating laser powder bed fusion are compared, and new equations for varied thermal conductivity and laser absorptivity are proposed.

The schematic of the heat source models, (a) cylindrical shape; (b) semi-spherical shape; (c) semi-ellipsoidal shape; (d) conical shape, (e) radiation transfer method; (f) ray-tracing method; (g) linearly decaying method; (h) exponentially decaying method.

“The physical phenomena associated in a melt pool are highly complicated, mainly controlled by mass and heat transfer,” the researchers explain. “The heating and cooling rates are extremely high due to the fast-moving laser irradiation on the powder particles. In addition, the dynamic melt pool development beneath the powder-bed, phase change dynamics from liquid to vapor and plasma, and powder particles drawn by high-speed metal vapor flux and capillary effects exist in the melt pool. Therefore, fine-scale numerical models, which included several details, such as laser-ray tracing in randomly distributed particles and thermal fluid dynamics, have been built in order to simulate several complex melt pool behaviors. However, the computational cost for such simulations is extremely high.”

Therefore, the researchers propose effective simulation models with certain approximations and assumptions to predict the dimensions of melt pools, in order to reduce the computational time.

Experiments were carried out on an EOS M 290 machine. A 3D heat transfer finite element model for laser powder bed fusion was developed for accurately predicting melt pool dimensions and surface features.

Temperature-dependent thermal material properties (a) density of SS17-4PH; (b) thermal conductivity of SS17-4PH; (c) heat capacity of SS17-4PH; (d) material properties of mild carbon steel.

“Based on the literature review, eight heat source models are used for the numerical modeling of LPBF and can be categorized as 1) geometrically modified group (GMG); and, 2) absorptivity profile group (APG),” the researchers state. “Experiments were carried out to validate the simulation results. All the eight heat source models lead to over 40% shallower melt pools compared with the experiments.”

Stainless steel powder particles

To improve the model performance, a mathematical model with varied anisotropically enhanced thermal conductivity and varied absorptivity was proposed and applied to the heat transfer simulation with the exponentially decaying heat source.

The researchers came to two main conclusions:

“The expressions of varied anisotropically enhanced thermal conductivity and varied absorptivity were linear algebraic equations,” they state. “Good agreement between the simulation and the experimental results was derived. The averaged error of melt pool width and depth are 2.9% and 7.3%, respectively.

“The proposed heat transfer model has been further validated by the surface features, track stability and ripple angle. For the track stability, the predicted results are in good agreement with the experimental results. In addition, the simulated ripple angles are within the range of experimental results.”

They also concluded that the heat source expressions can be linear while causing the simulation results to be in better agreement with both experimental melt pool dimensions and track surface morphology.

Authors of the paper include Zhidong Zhang, Yuze Huang, Adhitan Rani Kasinathan, Shahriar Imani Shahabad, Usman Ali, Yahya Mahmoodkhani, and Ehsan Toyserkani.

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It seems safe to say that self-healing materials are extremely fascinating. The 3D printing world has shown them increasing interest lately, with potential applications including electronic devices and cartilage replacements. Last summer, a team of researchers at the University of Manitoba created a new method of designing conductive, 3D printable, self-healing hydrogel materials to make them mechanically stable, which involved both physical and chemical cross-linking.

Schematic of the injectable “A+B” hydrogels using double barrel syringe, which are cross-linked by covalent bonds during or after injection.

3D hydrogels are hydrophilic polymeric networks cross-linked by either chemical covalent bonds, physical interactions, or a combination of the two. Because of the crosslinks between polymer chains and their hydrophilic nature, hydrogels can actually swell up to a hundred times, or even a thousand, of their dried mass without needing to be dissolved in water.

While hydrogels used to be pre-prepared and implanted into target sites within the human body during surgical procedures, they can now be easily injected from a syringe through a fine needle, making the material perfect for biomedical applications.

According to a dissertation, titled “Injectable Composite Hydrogels Based on Metal-Ligand Assembly for Biomedical Applications,” by Liyang Shi with Uppsala University in Sweden, injectable hydrogels are very useful in developing minimally invasive surgical procedures, as they “avoid damage of surrounding tissues during implantation surgery” and can easily fill defects with complex shapes in situ. In addition, it’s not difficult to 3D print injectable hydrogels so they form more advanced, customized morphology hydrogels by automating their extrusion from a syringe and programming the movement in a CAD file.

The abstract of Shi’s dissertation reads, “This thesis presents new strategies to construct injectable hydrogels and their various biomedical applications, such as 3D printing, regenerative medicine and drug delivery. These hydrogels cross-linked by dynamic metal-ligand coordination bonds exhibit shear-thinning and selfhealing properties, resulting in the unlimited time window for injection. Compared with nondynamic networks based on chemically reactive liquid polymer precursors that forms covalent bond during and/or post-injection, our injectable hydrogels with dynamic cross-linkages can be injected from an already cross-linked hydrogel state.”

Overview of various HA-BP based hydrogels presented in this thesis and biomedical applications for which the hydrogels were utilized. Derivatives HA-BP (i), HA-BP(ii), and HA-BP(iii) represent three different types of attachment of BP moieties to HA backbone.

Shi used hyaluronic acid (HA) as the polymer, because it is both biocompatible and biodegradable. First, it was modified with bisphosphonate (BP) as chelating (heterocyclic ring-shaped chemical compound) ligand.

“In the first part of this thesis, I presented the different chemical approaches to synthesize BP-modified HA (HA-BP) derivatives as well as HA derivatives dually modified with BP and acrylamide (Am) groups (Am-HA-BP). The structures of HA-BP derivatives were confirmed by NMR characterizations, e.g. by the peak at 2.18 ppm for methylene protons adjacent to the bridging carbon of BP in 1H-NMR spectrum and phosphorus peak at 18.27 ppm in 31P-NMR spectrum, respectively,” Shi continued. “In the next part, the hydrogels were constructed by simple mixing of HA-BP or Am-HA-BP solution with Ca2+ ions (Paper I), Ag+ ions (Paper II), calcium phosphonate coated silk microfibers (CaP@mSF) (Paper III), and magnesium silicate (MgSiO3) nanoparticles (Paper IV).”

The hydrogel precursors consisting of the polymer chain containing UV cross-linkable groups are ejected out from syringe at liquids which is followed by polymerization cross-linked in defect area using light.

The hydrogels created during the experiment “exhibited dynamic features” like shear-thinning and self-healing properties. Shi applied four types of hydrogels based in HA-BP to different biomedical applications, including 3D printing, wound healing, bone regeneration, and controlled delivery of anti-cancer drugs.

“Additionally, reversible coordination hydrogels were demonstrated to be further covalently cross-linked by UV light to form a secondary cross-linkage, allowing an increase of the strength and modulus of the hydrogels,” Shi wrote.” In the last part of this thesis, biomedical applications of these hydrogels were presented.”

Shi used a homemade 3D printer to extrude Am-HA-BP•Ca2+ hydrogel, before using UV radiation to create a 3D tube-like construct with multiple layers. Using a rat model with full-thickness skin defects, HA-BP•Ag+hydrogel was able to increase the wound healing process, along with the thickness of the rat’s new epidermal layer.

In addition, double cross-linked Am-HA-BP•CaP@mSF hydrogel was able to induce new bone to form, without having to add any biological factors or cells. Finally, the hydrogel loaded with anti-cancer drugs was prepared by mixing HA-BP solution with drug-loaded MgSiO3 nanoparticles; the released particles from this combination “were shown to be taken up by cancer cells to induce a toxic response.”

Preparation process and injectable properties of HA-BP•CaP@mSF hydrogel. The hydrogel is formed by addition HA-BP polymer binder to CaP@mSF dispersion, and cross-linking by the coordination bonds of BP groups on HA backbones and CaP on the microfibers. For visualization, alcian blue as a dye was dissolved in the hydrogel.

“In summary, this thesis presents metal-ligand coordination chemical strategies to build injectable hydrogels with dynamic cross-linking resulting in time-independent injection behavior. These hydrogels open new possibilities for use in biomedical areas,” Shi concluded.

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[Image: Alexander Raths/iStockphotos]

3D printing is a field ripe for research and exploration. Studies have been done on all things related to the technology, from

to

and everything in between. There is an overwhelming number of studies out there, but where are they all coming from? A new study entitled “

” is a study of studies, looking at where 3D printing studies are largely coming from, and who is conducting them.

The researchers used scientometrics, or the study of measuring and analyzing science, technology and innovation.

“Defined as developing ‘the quantitative methods of the research on the development of science as an informational process’, scientometrics include practices of measuring research quality and impact, understanding the process of scientific citations, mapping scientific fields and the use of indicators in research policy and management contexts,” the researchers explain. “As scientometrics can study many aspects of the dynamics of science and technology, the researches introduced tools and applications for science mapping and visualization of bibliometric networks, concepts, current state of the field and future research direction.”

They collected their data from the Web of Science database, looking at a period of 35 years, which is about how long 3D printing has been around. 11,529 bibliographic records were obtained and analyzed using VOS Viewer, a software tool for constructing and visualizing bibliographic networks.

“These networks may for instance include journals, researchers, or individual publications, and they can be constructed based on citation, bibliographic coupling, co-citation, or co-authorship relations,” the researchers add. “VOS Viewer also offers text mining functionality that can be used to construct and visualize co-occurrence networks of important terms extracted from a body of scientific literature.”

Perhaps unsurprisingly, the number of studies being conducted on 3D printing has increased progressively each year. The highest number of publications was in 2017, followed by 2016, 2015, and 2014 respectively. The lowest number of publications was one, from 1983, and consisted of the very first study on 3D printing: a paper entitled “3D – Profile Detection of Etched Patterns Using a Laser Scanner (3D – Scan Detection) for
Automatic Inspection of Printed-Circuit Boards.” If you’ve ever tried wading through the mass of studies surrounding 3D printing and wondered where it all began, there you have it.

Not only is the number of studies growing each year, it’s growing significantly. The number of studies doubled -and then some – for the first time in 2014, to 1,083 from 2013’s 483. Two years later, the number doubled once again, going from 1,860 in 2015 to 3,016 in 2016.

The United States was shown to be the world leader in the publication of 3D printing studies. However, the academic institution with the highest scientific impact is Nanyang Technological University in Singapore. The most productive author in the field so far is C.K. Chua. The highest scientific impact came from a 2010 paper entitled “Additive Manufacturing Technologies: Rapid Prototyping to Direct Digital Manufacturing.”

The major source of publication in 3D printing comes from conference proceedings papers. You can see the conference proceedings with the highest scientific impact below:

In terms of bioprinting papers, the United States was the leader again, followed by China and Germany.

“It is proven that academic productivity is a function of multidimensional combination of the academic researcher’s work: the scientific work, education and external relationships,” the researchers conclude. “Science mapping is a spatial representation of how disciplines, fields, specialties, documents and authors are related to each other. By using scientometrics, researchers can identify new and relevant challenges in their field of research.”

Authors of the paper include Raluca Marinescu and Anişor Nedelcu.

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Plastic is the least expensive, most used 3D printing material out there – as an example, right now on my desk, I have seven little animal figurines, and one tiny Pacman ghost, all 3D printed out of plastic. Of the plastics, ABS and PLA are the two most popular, and PLA (polylactic acid) is more rigid, easier to color, and considered to be more environmentally friendly than ABS. It’s a polymer from renewable resources, with excellent mechanical properties and fluidity, and its low toxicity makes it a good choice for applications in the medical field.

But, while PLA is good for 3D printing very detailed items, it’s also easier to break these items, though the material is less prone to breakage during extrusion-based 3D printing.

A collaborative team of researchers from the Shandong University of Technology, the Shandong Research Center of Engineering and Technology for Clean Energy, and Anhui Aile Door and Window System Engineering Co., Ltd. were interested in looking at the defects in PLA properties, like high brittleness, poor thermal stability, and low glass transition temperature, that limit its use in further applications. The researchers also wanted to see if they could modify PLA to make it better.

Graphical abstract

The team recently published a paper, titled “Effects of Lubricant and Toughening Agent on the Fluidity and Toughness of Poplar Powder-Reinforced Polylactic Acid 3D Printing Materials,” that presents and discusses the effects of wood flour, lubricant, and flexibilizer on the fluidity and impact strength of PLA 3D printing materials.

The abstract reads, “Three dimensional (3D) printing materials were manufactured with polylactic acid (PLA) and poplar powder using the twin screw extruder and 3D printing consumables extruder. Lubricant (TPW604) and toughening agent polyolefin elastomer (POE) were utilized to improve the fluidity and toughness of the materials. 3D printing materials were tested by infrared spectroscopy, X-ray diffraction, melt flow rate, rheology behavior, impact and scanning electron microscope. The results show that the poplar powder could decrease impact strength of PLA, the same as TPW604. Unlike poplar powder, TPW604 can improve the fluidity of 3D printing materials. And POE can fill the voids formed by poplar powder in PLA, enhance interface compatibility between poplar powder and PLA, and effectively improve the fluidity and impact strength of 3D printing materials.”

Filamentary 3D printing materials samples and 3D printing plate.

Materials for FDM 3D printing need to meet environmental requirements (i.e. be safe, non-irritating, and non-toxic), be suitable for melting temperature, and have low shrinkage and high mechanical strength.

In the past, other researchers have tried to reinforce and modify PLA materials by mixing them with materials like plastic polycaprolactone (PCL), hydroxyapatite, polyethylene glycol (PEG), and modified cellulose nanocrystals. But due to its low cost and rich source, fiber reinforcement is the most common way of modifying PLA.

Other researchers have added coconut shell powder to PLA, filled it with wood flour, and mixed it with wood flour, though results from the wood flour showed that it had a negative effect on the PLA’s rheology. So fiber can also negatively impact PLA, by increasing its viscosity and reducing its melt index, among other issues.

“As a kind of wood-plastic composite (WPC), wood/PLA composite has the disadvantages of WPC,” the researchers wrote. “The wood fiber could effectively improve the mechanical strength of PLA. Wood flour can not only be uniformly dispersed in PLA matrix, but also be effectively encapsulated by PLA macromolecule. But wood fiber would limit the movement of PLA macromolecular chains, which could result in a significant decrease in the crystallization capacity. The impact toughness of wood/PLA composites is poor and brittle fracture would occur when subjected to external force, which is similar to pure PLA.”

The researchers decided to give it a go anyway, and reinforced PLA with wood flour – more specifically, poplar powder – to make a new 3D printing material, and attempted to change the material’s fluidity and toughness by adding lubricant and a flexibilizer. The materials were fabricated with a 3D printing consumables extruder at 180 °C.

“Following are the main conclusions which can be drawn from the research: the addition of poplar powder was bad for the fluidity and toughness of PLA because of the agglomeration,” the researchers concluded. “Although the lubricant improved the fluidity, it reduced the impact strength of 3D printing materials. In addition, the effect of the toughening agent was up to the expectations. The POE not only could improve the fluidity and toughness of 3D printing materials, but also the higher the content, the better the property in a certain range because of the effect of POE on wood flour. As consideration, 3D printing materials prepared in this study not only could be applicable to 3D printing, but also be environmentally, friendly and promising in the field of printing.”

So while things did not go as well as the researchers might have hoped, their work can offer a theoretical basis for developing new 3D printing materials, in addition to providing “theoretical guidance for the scientific determination of application fields.”

Co-authors of the paper are Qingfa Zhang, Hongzhen Cai, Andong Zhang, Xiaona Lin, Weiming Yi, and Jibing Zhang.

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3D bioprinting isn’t just about the quest to print working organs, although that is the goal of many in the field. But it also has many more immediate applications, such as, for example, better wound dressings. In a thesis entitled “Design of a 3D printed nanocellulose based moisturizer for wound dressing applications,” a student named Cristian Ghibaudo discusses using 3D bioprinting to create better wound treatments. Ghibaudo points to a project called the Onskin project, for which the aim is to develop novel wound dressings based on microfibrillar cellulose, or MFC, and sustainable materials.

The concept was developed in four modules: the moisturizing module (M1), the absorbent module (M2), the barrier module (M3) and the support module (M4). The paper focuses on the moisturizing module, which has several requirements:

• The wound must be kept moist
• Wound exudate must be removed
• It must be mechanically stable under moderate compression and shear forces
• It must retain its shape to prevent maceration
• It must be 3D printable
• It must be skin friendly
• It must be sterile
• It should be able to be applied without causing any pain to the patient
• It should be available on demand
• It must allow for the daily tasks of the patient

Ghibaudo discusses the use of bioprinted nanocellulose hydrogels, with or without living cells included.

“A further improvement would be use MFC functionalized with cells, growth factors, antimicrobials and use this material as bioink for tailor-made wound dressings,” he adds. “Even printed electronics and biosensors could be integrated into the wound dressing construct, for a intelligent and personalized wound management.”

After the development and characterization of materials was completed, several wound dressing prototypes were 3D printed. Two types of prototypes were produced: flat and concave.

“For the printing it was used the BioX printer supplied from CELLINK, Figure 49, and it was used CELLINK start as support ink for the concave structure, Figure 50,” Ghibaudo states. ” A conical nozzle of 0.41mm was used for the concave structure while a conical nozzle of 0,25 mm was used for the flat structure, to have a better resolution. The time printing was around 7 hours for the convex structure while only 30 min for the slat structure.”

The concave prototype had several disadvantages, one being that it took seven hours to print. The 0.41mm nozzle created a low printing resolution, though a higher resolution would have required an even longer printing time. In addition, the channels in the prototype needed to be designed from the STL file; they could not be created automatically from the printing process.

The flat prototype, on the other hand, had good mechanical properties and high resolution, plus it printed in only 30 minutes. Thus, the flat prototype was selected as the best choice for the final model. Both prototypes were designed to cover an inner elbow wound, and the flat dressing showed itself to be flexible enough to cover the uneven surface.

“In the end, it is shown in this work the hydrogel MFC/alginate based characterization with rheological and mechanical test,” Ghibaudo explains. “The MFC1 and MFC8 properties were evaluated and compared with different amount of alginate in the compositions. The material chosen for this application is a combination of microfibrillated cellulose, enzymatic or carboxylmethylated, and alginate with a ratio 80:20.”

Once the best design was settled on, it was found that 3D printed wound dressings can be highly effective; both the material and the structure of the dressing met the requirements listed above.

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[Images: Cristian Ghibaudo]

There’s still time to save on Trends & Innovations in Dentistry, our three-day online event starting September 25. If you sign up by tomorrow, September 1, you’ll receive 23 percent savings.

Sign up for Trends & Innovations in Dentistry with an early bird discount through tomorrow, September 1

Learn the latest dentistry innovations in this conference-style online event with live guest speaker sessions, product demos and audience Q&A sessions, plus ongoing discussions broken out into various industry categories.

Speakers include industry thought leaders, like Samuel Wainwright, Dental Product Manager at Formlabs.

Samuel Wainwright, Dental Product Manager at Formlabs and class speaker

Check out the full speaker roster here.

All sessions are recorded and archived so you can watch any time. When you sign up at our early bird rate, you’ll also get immediate access to archival video recordings from related courses so you can start learning right away!

Want to learn about how 3D printing is making an impact across industries? You can also sign up for our other fall classes, 3D Printing in Metal and 3D Printing with Polymers, starting September 18 and October 16, respectively.

Optical images of SLA 3D printed complex-shaped parts. (a) Hollow glass; (b) gear wheel and (c) the spiral piece.

Stereolithography, also referred to as SLA and SL, was the first 3D printing method invented, and while for a long time it was only considered to be a prototyping solution, we’re long past those days. This versatile technology can produce accurate, high-resolution parts with smooth surfaces, diverse build sizes, consistent properties throughout, and can also access a wide range of material properties. All of these features explain why SLA is so often used now for applications in tooling and patterns, such as injection molding, investment casting, and thermoforming.

A group of researchers from Zhejiang University in China recently published a paper, titled “A cross-linking strategy with moderated pre-polymerization of resin for stereolithography,” with the Royal Society of Chemistry. The study explains how the team worked to improve stereolithography, by providing parts, 3D printed with SLA technology, with better mechanical properties.

The abstract reads, “Here, we demonstrate a cross-linking strategy used in the coating field to attain long chains for resin pre-polymerization to obtain final resin parts which can expand the application of SLA. Isophorone diisocyanate (IPDI), 2-hydroxyethyl methacrylate (HEMA) and polyethylene glycol (PEG)-based prepolymer have long chains, making it easier for them to form dense structures. However, the prepolymer has high viscosity and can solidify in the absence of a laser. Thus, three kinds of adjuvants were added to dilute the prepolymer to make the slurry suitable for 3D-printing. Slurries were cured with different laser powers and scanning speeds. Diluents are found to affect the curing properties differently. With the diluent 2-hydroxyethyl acrylate added into the prepolymer, shrinkage of printed parts is lower than 1.3%. With the diluent ethylene glycol monophenyl ether, the density range of printed parts is between 1.187 g cm⁻³ and 1.195 g cm⁻³, which is higher than that of commercial PVC and PET. The three resins vary in density and hardness within a small range when the scanning speeds change. A relatively flat surface, high density and hardness can be obtained when the laser power is at 195.5–350 mW. Resin with this cross-linking strategy can expand the underutilized stereolithography’s application from prototyping to actual parts by producing more functional components with excellent performance.”

The slurry synthesis and stereolithography process of the whole process.

The researchers explained that SLA is not often used for final parts production, which is why there’s “a need to continuously improve existing processes and materials.” They aimed to do so with a cross-linking strategy popular in coating technology.

SEM images of an unpolished resin sample (type 3, 1000 mW, 100 mm s−1). (a) The front surface of the resin sample; (b) and (c) the side surface of the resin sample.

“In the fabrication of polymer coating, one of the strategies is to allow isocyanates to react with hydroxyl compounds to get radiation curable coating slurries,” the researchers explained. “The polyurethane resin, made of, e.g., IPDI, has excellent higher surface energy, photo-stability and chemical resistance and it is commonly used in paints, coatings, printing stamps and adhesion agents. HEMA is one of poly-acrylate derivates among acrylate-based resin, and acrylate-based monomers are used widely because of their low cytotoxicity and high heat resistance, while acrylate-based resin is prone to have a slower curing rate. Multifunctional monomers are applied to introduce more crosslinking sites, accelerate the curing rate and enhance the mechanical properties of the cured resin.”

They used HEMA, IDPI, and PEG to make the pre-polymer, and added diluents agents to modify the resin’s viscosity, because the pre-polymerization slurry was too sticky to use for SLA.

The researchers explained, “Viscosity is an important parameter to ensure good quality of SLA-printed parts. When the scarper forms a new layer, it is necessary to wait until the resin surface becomes completely flat in order to have accurate thickness control. Low-viscosity slurries are usually preferred as they allow better resin flow to replenish each layer during printing and also make handling easy (refilling and cleaning the resin tank more convenient).”

Photograph of a cubic resin sample with a size of 10 mm × 10 mm × 10 mm

After adjusting the software to match the slurries’ viscosity, the team 3D printed several 10 x 10 x 10 mm sample squares. After adjusting the laser power and scanner speed as well, they discovered that the three kinds of slurry had different typing ranges.

The researchers were able to show that that the crosslinking strategy of polyurethane-acrylate polymer could be applied for pre-polymerization in the resin slurry’s 3D printing synthesis. They also demonstrated that resin characteristics can be tailored for use in different applications by using variations of diluents.

“With 2-hydroxyethyl acrylate as diluents, the slurry can be used in high precision manufacturing, and the shrinkage of final parts is smaller than 1.3%. With ethylene glycol monophenyl ether as diluents, the density of final parts is larger than that of PVC and PET, which is comparable to the density of PC. The individual samples are uniform in the interior, and the front and side after polishing have similar surface quality and hardness. The laser scans with low power and high speed resulting in incomplete curing, while low speed and high power may cause over-polymerization,” the researchers concluded. “Together, our results provide important technique information for exploring polymer-based stereolithography in manufacturing of more complex functional parts.”

Co-authors of the paper include Rongping Ni, Bin Qian, Chang Liu, Xiaofeng Liu, and Jianrong Qiu.

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It’s an unfortunate fact that a lot of things can go wrong when 3D printing. Many people who are unfamiliar with the technology think that it’s like magic: you just press a button and out pops a finished, perfect part. But with every 3D printing technology comes its own problems, and there are plenty in FDM/FFF technology. Poor adhesion, warping, nozzle clogging, and spectacular meltdowns that seem to happen for no apparent reason – they’re all part of the 3D printing adventure.

One of the biggest issues that causes prints to fail or come out imperfectly is moisture. Many polymer filaments are hydrophilic, which means that they like moisture and will happily absorb it from the air surrounding them – that’s why spools of filament commonly come in airtight containers with little desiccant bags in there with them. This is particularly true for materials like PLA and nylon, which are more hydrophilic than others. So what happens when filament absorbs moisture?

3D printing filaments are made from polymers, which are in turn made up of multiple monomers joined together. Those polymer chains can break down, however, or depolymerize, and one way that this can happen is a process called hydrolysis, which is when a water molecule breaks a polymer chain. So when a supply of filament gets wet and is then extruded, the water inside it vaporizes, causing air bubbles and voids – you’ll know this has happened if you start hearing snapping and crackling noises while printing.

This can weaken material and cause poor inter-layer adhesion, as well as poor surface finish. It’s just not a good thing, but unfortunately it’s all too easy for filament to draw in water from the atmosphere and get messed up. On the bright side, the damage is not irreversible, if you dry the filament out before you extrude it. For this purpose, there are filament-drying products, and one of the newest is the Apium Filament Dryer from German company Apium.

Apium is focused on industrial 3D printing solutions, a leader in PEEK and other high performance polymers. The Apium Filament Dryer was developed in partnership with Singapore’s Purpose AM Systems and promises less oozing, stringy filament caused by moisture absorption, as well as better interlayer adhesion and mechanical properties.

“Through our partnership with Purpose AM, we are launching Apium Filament Dryers and provide our end-users with the complete solution for processing high performance polymers,” said Pinar Karakas, Head of Marketing and Quality Management at Apium. “We offer the unique AM solution with our advanced customer support established by our Service Center experts and forerunner technologies.”

The Apium Filament Dryer has thermally insulated walls, which reduces heat loss, and offers front loading which enables easy filament interchange. It has a rotary desiccant system for the dehumidification of incoming air, as well as a set of HEPA and active carbon filters. It is compatible with all Apium P Series 3D printers and Apium filaments, as well as several other open-system 3D printers.

Apium is ready to ship the filament dryers upon order and offers a 12-month warranty.

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Phantoms are models of organs that can be created to test things like proper medication dosage, for example. In a paper entitled “Recent advances on the development of phantoms using 3D printing for imaging with CT, MRI, PET, SPECT, and ultrasound,” a research team discusses the 3D printing of phantoms.

“Printing technology, capable of producing three‐dimensional (3D) objects, has evolved in recent years and provides potential for developing reproducible and sophisticated physical phantoms,” the researchers state. “3D printing technology can help rapidly develop relatively low cost phantoms with appropriate complexities, which are useful in imaging or dosimetry measurements. The need for more realistic phantoms is emerging since imaging systems are now capable of acquiring multimodal and multiparametric data.”

Three questions are posed by the researchers:

• Is the resolution of 3D printers sufficient for existing imaging technologies?
• Can materials of 3D printed phantoms produce realistic images representing various tissues and organs as taken by different imaging modalities such as computer tomography (CT), positron emission tomography (PET), single‐photon emission computed tomography (SPECT), magnetic resonance imaging (MRI), ultrasound (US), and mammography?
• How feasible or easy is it to print radioactive or nonradioactive solutions during the printing process?

The researchers review several published cases of 3D printed phantoms of multiple parts of the body. The resolution of the 3D printers used is, according to them, sufficient for 3D printing phantoms.

“However, better coverage of materials would have been helpful to develop realistic phantoms, achieving sizes of tissues and organs comparable to those of humans and animals,” they add. “The materials of the printers are yet to demonstrate the extent of what is required for tissues or organs so that they can be used in multimodality hybrid imaging. In addition, there have been only limited discussions or investigations on how the radioactive solutions may affect the properties of the 3D‐printed materials.”

There is a lot of potential for growth in this area, the researchers continue, but companies that develop the 3D printers and materials should consider a wider range of material properties useful in medical imaging. They also propose the development of a 3D printer specifically designed for 3D printing phantoms.

Sub‐resolution sandwich phantom with radioactive paper sheets between each slab

“3D‐printed phantoms will be pivotal in the evolution of the medical imaging field, as they give the opportunity to test and improve several aspects of the scanners’ hardware and software,” the researchers conclude. “At the moment, it is feasible to use some specific phantoms for two or three imaging modalities, however, the technology requires further improvement for use with multimodality systems.”

The paper is an extremely detailed look at the many 3D printers and materials used to 3D print phantoms, and it also suggests looking more toward the bioprinting of phantoms for better biological realism. Soft, moving 3D printed phantoms are discussed, as well as phantoms containing fluids and radiotracers. 50 studies are discussed in total, and overall the researchers conclude that 3D printing is an effective method of producing phantoms – and that it has a lot more potential to do so in the future.

Authors of the paper are Valeria Filippou and Charalampos Tsoumpas.

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