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Plant-Derived Photoinitiator Free Resins as Alternatives to Petroleum-Based Photopolymers

In a paper entitled “Photoinitiator Free Resins Composed of Plant-Derived Monomers for the Optical µ-3D Printing of Thermosets,” a group of researchers discusses their investigation of acrylated epoxidized soybean oil (AESO) and mixtures of AESO and vanillin dimethacrylate (VDM) or vanillin diacrylate (VDA) as photosensitive resins for optical 3D printing without any photoinitiator and solvent. Natural oils like these, according to the researchers, are some of the best alternatives to petroleum-based resins.

UV/VIS curing tests were performed on pure AESO and two resin series: AESO/VDM and AESO/VDA. Chemical structure analysis was also performed, as well as Soxhlet extraction, differential scanning calorimetry, thermogravimetric analysis and mechanical testing. The researchers then experimented with the resins using direct laser writing 3D lithography.

“It is known that the acrylic group is more reactive than methacrylic,” the researchers state. “This explains the increase of the induction period and tgel value during the photocross-linking of the resin series AESO/VDM in comparison to AESO. Additionally, the slope of the G’ curve of AESO was steeper than that of the resin series AESO/VDM indicating the quicker formation of the polymer network [50]. High G’ values indicate better mechanical properties of polymers caused by the high density of cross-links. Thus, the higher G’ values of AESO indicate the higher density of cross-links in this polymer (pAESO).”

The researchers discovered through their experiments that AESO tends to form densely cross-linked polymers even without photoinitiators. AESO and AESO/VDM1, they add, can be “great candidates” as renewable materials for DLW 3D lithography.

“It is envisaged that the photostructuring without the photoinitiators is beneficial for the fields of biomedicine, micro-optics and nanophotonics,” they continue. “The avoidance of toxic photoinitiators increases the integrity of biodegradable cell-growth scaffolds and reduces the auto-fluorescence while performing microscopy in vitro or in vivo. The absorbing materials are detrimental for the use in micro-optics and nanophotonics due to their reduced optical resilience and induced signal losses. Moreover, the use of plant-derived materials in such technologies would benefit greatly due to their low toxicity, high biodegradability, and improved recycling options. Finally, it would reduce the dependency on limited and increasingly expensive fossil resources as well as greenhouse gas emission, which are the targets of the European Commission initiated ‘Europe 2020’ strategy.”

The researchers’ real-time photorheometry study “revealed the higher rate of photocross-linking of pure acrylated epoxidized soybean oil than that of its mixture with vanillin dimethacrylate or vanillin diacrylate without a photoinitiator and solvent.” The addition of vanillin dimethacrylate reduced the rate of photocross-linking the values of the glass transition temperature, thermal decomposition temperature and compressive modulus.

“The formation of more linear and/or branched macromolecules considered the vanillin dimethacrylate effect as a plasticizer for acrylated epoxidized soybean oil in photocross-linking without a photoinitiator,” the researchers conclude. “It was experimentally demonstrated that the homopolymer of acrylated epoxidized suitable materials for rapid 3D microstructuring by the direct laser writing lithography technique.”

Since photoinitiators can cause skin irritations and long term contact allergies in people working with them in liquid form, this may be a very good development for those who process DLP and stereolithography parts. Perhaps it would be safer in the final part as well. Any developments in 3D printing materials can now make all existing compatible materials safer and perhaps less expensive so these kinds of developments have to be applauded.

Authors of the paper include Migle Lebedevaite, Jolita Ostrauskaite, Edvinas Skliutas and Mangirdas Malinauskas.

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Fortify raises $2.5 million to advance composite 3D printing technology

Fortify, the Digital Composite Manufacturing (DCM) company and recent winner of the Formnext 2018 startup challenge, has raised $2.5 million in seed funding. Provided by five strategic investors, the money has been used to expand the Fortify team and create new potential partnership opportunities. To begin later this year, the company is also seeking a further […]

Preview: the 3D printed creepy crawlies of Prototyping in Tokyo, Japan House London

This week 3D Printing Industry was invited to Kensington High Street, one of the most affluent retail locations in London, for an exhibition preview featuring the cutting edge of additive manufacturing and robotics. Located in Japan House, a cultural centre, restaurant and store celebrating the best of the East Asian nation’s design, Prototyping in Tokyo showcases the […]

Researchers Test PLA CaC03 Composite Materials to Make 3D Printed Splints

In a paper entitled “Novel PLA-CaCO3 Composites in Additive Manufacturing of Upper Limb Casts and Orthotics—A Feasibility Study,” a group of researchers looks at 3D printing to treat upper limb injuries, which are, they say, “among the most common injuries worldwide.” While bone fractures are traditionally treated with plaster casts, new treatments have been used experimentally, including 3D printing to create a cast personalized to the patient’s needs.

The researchers tested three different materials’ potential for use in 3D printed casts; two of those materials were new. They used unique filaments from Hungarian company Filamania. These composite materials were compared to standard PLA polymers. The composites were made from PLA mixed with fine CaCO3 powder. First made by designer Carmen Brio a few years ago this type of material has interesting properties.

“The ‘PLA Modell’ (M): contained 20 m/m% of CaCO3 and ‘PLA Gypsum’ (G) 50 m/m% of CaCO3,” the researchers explain.

Mechanical tests were performed on the materials, including a Charpy Impact Test, a three-point bending test, tensile strength test and Shore D hardness test. The researchers then investigated the materials in terms of possible production for splints or casts. First they examined thermoforming, then 3D scanned a healthy volunteer’s hand to create a CAD model, which was then 3D printed.

The researchers found that 3D scanning and 3D printing was more costly and time-consuming than thermoforming; however, the 3D technology resulted in a better fit. The volunteer stated that the 3D printed cast provided more stability, which is critical for healing. While 3D printing is more expensive than traditional plaster cast methods, the researchers state, the costs are getting closer.

With the addition of CaCO3 to the PLA, the materials’ dynamic and static properties were altered significantly. Namely, they became more rigid and brittle. They were very easy to thermoform, however, as well as to 3D print, and they were easily obtained, making them good candidates for the production of casts and splints.

“The static tests and Shore D measurements indicate that the materials can be also used for medical modelling (for example: bone models for IO – intraousseous cannulation – trainers, teeth models for skills training, and individualized training of bone synthesis procedures),” the researchers conclude. “Our recent study– analysing the thermal behaviour of these materials – have shown that these materials are suitable for disinfection procedures also, which is an important feature in clinical applications. For long-term results, clinical, patient-related studies have to be carried out in the near future, along with detailed market research, focusing on IP (intellectual property) relations also.”

The researchers point out that one drawback of 3D printing is its typically slow speed; waiting in the emergency room for 19 hours for a cast to be ready is not an option. However, using a temporary cast until a better one can be 3D printed is a possibility, and the researchers anticipate that 3D printing speeds will soon evolve to an acceptable range. In terms of 3D scanning, while the researchers were able to use a healthy individual to create a model, most patients with fractures will need to have their opposite limb scanned to create a proper fit.

Authors of the paper include Péter Varga, Denes Lorinczy, Luca Tóth, Atilla Pentek, Miklos Nyitrai and Peter Maroti.

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Spinal Cord Implant Promotes Nerve Cell Growth

Researchers at University of California San Diego School of Medicine and Institute of Engineering in Medicine have developed a spinal cord implant that could potentially revolutionise the way we repair nerve tissue. The implant is a 2mm replica spinal cord with a scaffolding that contains neural stem cells. Researchers recently tested it, showing improvements in regeneration in rats. […]

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China National Space Administration to establish 3D printed houses on the moon

The China National Space Administration (CNSA) has announced plans to be the first country to establish a base on the moon, and it will be built using 3D printing technology. CNSA officials made the declaration yesterday in Beijing during a press conference for the State Council Information Office (SCIO). This conference was held following the […]

Inside the X1 25PRO mid-scale additive manufacturing platform from ExOne

The X1 25PRO™ is the latest metal binder jetting additive manufacturing system from Pennsylvania-headquartered industrial 3D printing systems and services provider ExOne (NASDAQ:XONE). With the fine, metal injection molding (MIM) powder-handling capabilities of the company’s INNOVENT+™ research 3D printer and larger, mid-scale 3D printed production, this machine is leading the charge for ExOne among burgeoning […]

New Polypropylene Powder with Superior Processing and Part Characteristics for Laser Sintering Process

AM Polymer Research GmbH presents its third series material, a polypropylene powder from the ROLASERIT® family. The developed ROLASERIT® PP01OF1 thus makes this important standard plastic available for laser sintering. The material has very good processing properties. The processing of the material has already been successfully demonstrated without problems on various common laser sintering systems, and is used by several service providers for part production. According to the company’s philosophy of selling only final-qualified materials, only short running-in times on the machines are necessary. Thus, the production of customer parts is possible within a few days. In particular, the material has no tendency to curling or distortion, which makes it easy to achieve robust processing conditions.

The components have good mechanical properties and, in contrast to many other new material developments for laser sintering, exhibit ductile component behavior with elongation at break of over 30%. The range of applications for manufactured components is therefore diverse and ranges from simple housings to function-integrated parts with film hinges. The material costs are significantly lower than those of conventional standard materials, so that the use of the material offers economic advantages for many component groups.

As early as 2013, an elastic TPU material called ROLASERIT® PB for laser sintering was launched on the market as the first material of AM Polymer Research. It is characterized by very good flow behavior and multiple 100% reusability. Processing is possible on all common laser sintering systems. Here no disturbing smoke development occurs, whereby a simple exposure of the hatch is sufficient. The components produced with the material show elongations at break of sometimes more than 500 % and even in z-direction more than 300 %, have very good surface properties and high edge sharpness with good detail resolution. In addition, the hardness that can be produced can be variably adjusted between 70 and 85 Shore A by means of process settings. The components can also be used directly without infiltration and can be easily colored.AM Polymer Research GmbH has thus developed three different thermoplastic powders for laser sintering or powder bed fusion and distributes them under the brand name ROLASERIT®.

A grey-black polyethylene material ROLASERIT® PEGR completes the material range. The material was developed as an entry material for simple, inexpensive prototypes and makes the mass plastic polyethylene available for the laser sintering process. Like the previously developed material, the powder has very good powder flowability. Processing is also simple. The parts exhibit characteristic PE strength values with easily manageable component ductility. Due to the component properties typical for PE with low component hardness, the components can be finished very well.

In addition to the commercialized products, other important standard thermoplastics such as PA6 or PBT are under development for laser sintering. The current state of development already shows promising properties of these future products. In order to be able to react even more flexible to development trends in the future, a production facility with three production lines for powder production and refinement as well as the AM Application Center with an expanded laboratory are currently being built at the Willich site. Within this framework, a powder spherical shaping line will also be set up by the end of 2018. With this system, the properties of the powders produced can be further improved. The machine can be used to refine materials on a several tenth of ton scale.AM Polymer Research GmbH, headquartered in Duisburg, is a spin-off from the University of Duisburg-Essen and was founded in 2014. The company specializes in the development, production and sale of laser sintering materials as well as the development of requirements-oriented materials in the field of additive manufacturing processes. The team of the company can look back on many years of experience in the field of additive manufacturing processes. The founders Dr.-Ing. Andreas Wegner and Prof. Dr.-Ing. habil. Gerd Witt has ten respectively twenty years of experience in laser sintering of plastics. In 2015, the company set up its own AM Application Center with laboratory in Krefeld. Timur Ünlü, a long-time expert in the field of powder production, joined the company in 2018.


	Contact

AM Polymer Research GmbH

Dr.-Ing. Andreas Wegner

Bismarckstraße 120

47057 Duisburg

Deutschland

Tel.: +49 203 306 4880

E-Mail: info@am-polymer-research.de

Homepage: http://www.am-polymer-research.de/

When Should 3D Printing Be Used in Sand Casting?

Complex casting with 3D printed mold (left) and traditional casting with traditional cores and molds (right)

Sand casting is a technology with a long history, but it’s being reinvented by additive manufacturing. 3D printed sand molds allow for highly geometrically complex castings, and in a paper entitled “Economies of Complexity of 3D Printed Sand Molds for Casting,” a group of researchers outlines the benefits of using additive manufacturing in sand casting:

the integration of structural elements such as periodic lattices in order to optimize weight versus strength
the structural inclusion of unique features such as embossed part numbers and/or other details of the production history
complex geometries that generate new casting applications not possible previously

In the paper, the researchers describe a complexity evaluation tool that scores CAD models to determine the most economical casting approach based on slicing and 2D geometry evaluation. The three potential outcomes include traditional sand casting; AM-enabled sand casting and a hybrid of the two with 3D printed cores in traditional casting flasks.

“Four algorithms were developed that all began by slicing each of the benchmark STL files and performing analysis per layer producing an average complexity across all layers,” the researchers explain. “This process was repeated for three orientations of each part and the results were averaged including: an unrotated case, a rotated case 90 degrees in X axis and rotated 90 degrees in Y axis. The rotations were completed in order to detect a complexity bias relative to orientation. For each orientation, the complexity numbers from all layers were individually calculated and then the total was divided by the number of layers for a mean value that was independent of the number of slices selected. By using more layers, the accuracy was expected to improve by improving the statistical sampling; however each additional layer meant an increase in the duration of computation.”

The complexity factor values for Algorithms AD are shown for each of the benchmark castings. E indicates exterior. I indicates interior.

Algorithm A was the simplest and summed the number of contours detected for each layer. Algorithm B was similar to A except that instead of incrementing the sum of contours, a ration was calculated and added to a running sum. Algorithm C summed the number of contours but also included a sum of concavity defects that were sufficiently concave. Algorithm D was an aggregate of the other algorithms: the contours, the ratio of perimeter over area and the number of concavity defects summed together.

16 structures were selected for casting, ranging in complexity from simple spheres to a gyroid matrix and a Voronoi tesselation chess piece. The different castings were run through the complexity software, and the resulting data was compared to complexity scores assigned by previous work in which the scores were generated manually and correlated well with the decision as to which casting process was most suitable.

Of the four algorithms, Algorithm D gave values that “provide a decision boundary that was in line with the intuition of the authors as well as obvious extreme cases (sphere as a case of simplicity or a gyroid matrix for a case that can only be cast with the help of 3D printing),” according to the researchers.

“This layerwise complexity factor was compared to a known complexity factor for conventional casting fabrication method and showed similar results but without requiring design knowledge of the traditional methods,” the researchers state. “The economics of complexity and quantity were shown for a traditional casting tooling method and then compared to three methods that involved additive manufacturing.”

The researchers presented four options:

Traditional manufacturing (TM): Traditional subtractive processes to make molds / cores.
3D Sand Printing (3DSP): Complete sand printing of both molds and cores.
3D Sand Printed Core (3DSPC): 3D sand printing of cores and conventional pattern making for the mold cope and drag.
FDM Patternmaking (FDMP): Conventional core making and 3D printing using fused deposition modeling of hard patterns for conventional mold making with the advantage of faster mold fabrication.

The most economical method depended on the complexity and quantity of the parts being made. For example, for an air brake, 3DSP was the most cost effective regardless of level of complexity. However, 3DSPC was the most cost effective for more complex objects or objects in quantities of 100 or higher. For castings of low complexity, FDMP was the best choice, while for quantities of 1,000 3DSPC was the most cost effective for the full range of complexities.

Authors of the paper include Ashley Martof, Ram Gullapalli, Jon Kelly, Allison Rea, Brandon Lamoncha, Jason M. Walker, Brett Conner and Eric MacDonald.

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FELIXprinters debuts Pro 3 desktop 3D printer – technical specifications and pricing

FELIXprinters, a Netherlands-based desktop 3D printer manufacturer, has released its latest additive manufacturing system, the Pro 3, designed to maximize productivity and efficiency. “The Pro 3 has been developed to integrate seamlessly into industrial workflows, whether that is in an office, a workshop, lab or factory environment,” said Guillaume Feliksdal, Founder and Director of FELIXprinters. […]