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Strengths of Three Materials Combine to Form Composite 3D Printed Components

In a paper entitled “On the 3D printing of recycled ABS, PLA and HIPS thermoplastics for structural applications,” a group of researchers discusses multi-material 3D printing for structural applications. The materials they use are recycled ABS, PLA and HIPS to create composite parts. The point was to combine the materials so that the final component benefited from the respective strengths of each material.

“ABS is amorphous in nature and having high impact resistance,” the researchers state. “Low thermal conductivity, heat resistance and toughness, bio-degradability and bio-compatibilities are the key advantages of PLA, whereas HIPS is a low strength structural polymer which have better machinability and fabrication characteristics with low cost.”

The researchers 3D printed the sample components, which had four layers of each material. Testing was then performed on the components, including MFI characterization, differential scanning calorimetric (DSC) analysis, tensile testing, Lee’s disc thermal conductivity measurement, flexural testing and pull out testing. ABS, PLA and HIPS were found, through DSC testing, to be compatible with each other, all of them having similar ranges of integral heat value.

“As the practical application requires the requirement for maximum strength with minimum elongation, HIPS was having most desired elongation and PLA was having most desired tensile strength values,” the researchers continue. “After 3D printing of multi-material component, it was observed that tensile strength and elongation values of all multi-material printed components were observed intermediate to the HIPS and ABS which shows the usefulness of present study.”

Several conclusions were made from the study, as stated by the researchers:

In tensile testing, the Young’s modulus of multi-material component (325 MPa) was observed higher at experiment number 3, than single thermoplastic (Young’s modulus of PLA 47.9 MPa, ABS of 175 MPa and for HIPS 112.5 MPa).
Pull out testing revealed the fact that elongation and strength properties of 3D printing can be controlled through multi-material printing at predicted input processing setting. It was noted that break elongation of multi-material components was observed smaller as compared to ABS and PLA. At the same time, break load and break strength has been observed greater than HIPS in case of pull out tests.
3D printing of multi-material components at predicted settings resulted in the observation that flexural strength was attained higher than HIPS (2.01 MPa) material as 2.96 MPa but lower than PLA (9.07 MPA) and ABS (7.04 MPa).
It was noted that PLA was having thermal conductivity of 0.2225 W/m.K, ABS of 0.1722W/m.K and HIPS of 0.3232W/m.K. For structural applications, it requires the thermal conductivity to be desired minimum. Multi-material printing of these materials resulted in thermal conductivity of 0.2732W/m.K (dt/dT = 0.814 K/s) which was lesser than HIPS material shows the utility of multi-material 3D printing.

Overall, the three materials were compatible with each other, and their strengths worked together to create composite components that were superior to single-material components. With the growing sophistication of 3D printers, and the greater accessibility of printers with multimaterial capabilities, it is becoming easier to 3D print composite components like these for functional applications that benefit from the best characteristics of ABS, PLA and HIPS.

Authors of the paper include Ranvijay Kumar, Rupinder Singh and Ilenia Farina.

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3D Printed PLA and PCL Composite Biodegradable Stents Show Promise

PCL (white) and PLA (black) stents

Biodegradable stents have shown great potential in reducing complications in patients, but they require further study, according to the authors of a paper entitled “3D-Printed PCL/PLA Composite Stents: Towards a New Solution to Cardiovascular Problems.” The researchers outline five main requirements that a biodegradable stent must meet:

Their manufacturing process should be precise
Degradation should have minimal toxicity
The rate of degradation should match the recovery rate of vascular tissue
They should induce rapid endothelialization to restore the functions of vascular tissue but should at the same time reduce the risk of restenosis
Their mechanical behavior should comply with medical requirements, particularly the flexibility required to facilitate placement but also sufficient radial rigidity to support the vessel

Although the first three requirements have been thoroughly studied, according to the researchers, the last two have been overlooked. A possible way of addressing these issues would be to create composite stents using materials that have different mechanical, biological or medical properties, such as PLA or PCL. Fabricating stents with these materials using laser cutting, however – the traditional method of manufacturing stents – would not be possible. The researchers, therefore, decided to produce them using 3D printing.

They 3D printed the stents using a tubular 3D printer. The stents were then seeded with cells and left for three days, and then tests were performed to assess the morphological features, cell proliferation, cell adhesion, degradation rate and radial behavior.

“The results prove the materials’ biological compatibility and encourage us to believe that PCL/PLA composite stents would comply with the fourth requirement, i.e., rapid endothelization without risk of restenosis,” the researchers state. “PCL’s better cell proliferation may be useful to increase the proliferation of endothelial vessel cells in the external wall of the stents, while an internal PLA wall may help to reduce the proliferation of cells that produce restenosis. However, further studies with other kinds of cells or substances need to be performed to confirm this. The results here show low cell proliferation because of the small amount of material that the stents have. Additional studies that use longer culture times may be beneficial to obtain better proliferation results.”

The researchers’ initial hypothesis was confirmed: the smaller the cell area of the stent, the better the cell proliferation rate. The cell shape of the stent, however, did not show any significant influence. Because of their different molecular weights, PCL showed better cell proliferation than PLA. PLA showed a much faster degradation rate, which limits its use for biodegradable stents. Radial behavior results show that composite PLA/PCL stents could be used to improve each material’s separate limitations, with PCL offering elasticity in the expansion stem and PLA providing rigidity in the recoil step.

Overall, 3D printing proved itself to be a promising method for producing stents. Both PCL and PLA showed themselves to be biocompatible, and the composite stents showed the most promise, with medium levels of degradation rates and mechanical modulus.

“Based on the results presented here, we believe that polymer composite stents manufactured with 3D-printing processes could be a highly effective solution to the current problems that stents made of polymers have,” the researchers conclude. However, FDA rules currently limit the use of 3D-printed stents in real clinical applications and, although PCL and PLA are FDA-approved materials, there are still open challenges to be met before approval for 3D-printed implantable medical devices can be obtained.”

Authors of the paper include Antonio J. Guerra, Paula Cano, Marc Rabionet, Teresa Puig and Joaquim Ciurana.

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The Effect of Temperature on 3D Printed PLA Clay Nanocomposites

In a paper entitled “3D Printing of PLA/clay Nanocomposites: Influence of Printing Temperature on Printed Samples Properties,” a group of researchers investigate the possibility of using a layered silicate-reinforced PLA in 3D printing applications. In particular, they examine the influence of printing temperature in 3D printing clay/PLA nanocomposites.

“For this reason, two PLA grades (4032D and 2003D, D-isomer content 1.5 and 4, respectively) were melt-compounded by a twin screw extruder with a layered silicate (Cloisite 30B) at 4 wt %,” the researchers explain. “Then, PLA and PLA/clay feedstock filaments (diameter 1.75 mm) were produced using a single screw extruder.”

The researchers 3D printed dog-bone-shaped and prismatic specimens using FDM 3D printing at three different temperatures, which were progressively increased from the melting temperature (185–200–215 °C for PLA 4032D and 165–180–195 °C for PLA 2003D). The PLA and PLA/clay specimens were characterized using thermogravimetric analysis (TGA) dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and tensile tests.

The morphology of the 3D printed specimens was also investigated using optical microscopy and contact angle measurements. DMA on the PLA/clay filaments showed an increase in storage modulus both at ambient temperature and above the glass transition temperatures compared to regular PLA filaments. The presence of nanoclay also increased thermal stability, demonstrated by TGA, and acted as a nucleating agent, which was observed by the DSC measurements.

“Finally, for 3D printed samples, when increasing printing temperature, a different behavior was observed for the two PLA grades and their nanocomposites,” the researchers state. “In particular, 3D printed nanocomposite samples exhibited higher elastic modulus than neat PLA specimens, but for PLA 4032D+C30B, elastic modulus increased at increasing printing temperature while for PLA 2003D+C30B slightly decreased. Such different behavior can be explained considering the different polymer macromolecular structure and the different nanocomposite morphology (exfoliated in PLA 4032D matrix and intercalated in PLA 2003D matrix).”

One of the reasons the researchers give for conducting the study is that PLA, while a popular 3D printing material, has several issues including low thermal stability, crystallization ability, and drawability. A possibility for overcoming these drawbacks is to reinforce PLA with nanofillers such as layered silicates, carbon nanotubes, and so on. The use of filler at the nanoscale allows for improvement of both the materials’ properties and processability. Few scientific studies have looked at the printability of PLA/clay nanocomposites, however.

In addition to the increase of the elastic modulus with the increase of the printing temperature, the researchers found that the properties of the 3D printed specimens were strongly affected by the different polymer matrices and the resulting nanocomposite morphologies. The different macromolecular architecture of the two matrixes affected the polymer’s ability to orient or not. The printing temperature also had an effect on the 3D printed specimen transparency – the higher the printing temperature, the higher the transparency.

“This study demonstrated that printing temperature should be chosen considering not only melting temperature, but also polymer architecture and/or nanocomposite morphology in the case of nanocomposite systems,” the researchers conclude. “Therefore, potential applications could be found in both considering the improvement in mechanical properties, if the correct temperature is used, and physical/aesthetical properties such as different degree of transparency.”

Authors of the paper include Bartolomeo Coppola, Nicola Cappetti, Luciano Di Maio, Paola Scarfato and Loredana Incarnato.

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Print Your Mind 3D Launches 3D Printer Filament Recycling Challenge for High School Students

In response to the ever-growing problem of 3D printing filament waste, Calgary-based professional desktop 3D printer provider and social enterprise Print Your Mind 3D, which works to always practice business in a socially responsible way, is tasking high school students in Alberta with crowdsourcing viable solutions to turn this wasted plastic into useful products and tools. This is the focus of the company’s latest challenge for its Enviromakers initiative, which aims to build a community of makers, designers, and engineers to work together to create solutions, using 3D printing, for real-world problems.

“From functional prints for everyday use, to medical and even aerospace engineering applications 3D printing is changing the way we design, prototype and create. As this usage continues to rise, sustainable measures and practices are becoming a larger and larger priority. While 3D printing provides a much cheaper and somewhat environmentally friendly option, as anyone with a 3D printer knows, filament waste tends to build up fairly quickly. This waste comes in the form of support material, failed print, and obsolete projects,” the background for the PLA Recycling Challenge reads.

“This competition aims to utilize 3D printed waste filament as an opportunity to educate students about the importance of sustainable development, technology and practices. Furthermore, we challenge students to propose creative and innovative ways to recycle or reuse waste filament in their local community.”

The challenge is open to any Alberta student in grades 10-12, though it’s recommended to have a teacher help champion a team. Participants must propose and develop a plan for either converting waste PLA material, or reusing it, in order to make a new tool or product. The plan has to include everything that would needed to execute the idea, in addition to a clearly articulated description of how it will be used and what makes it different. Students can create an entirely new idea, or build and improve upon previous applications.

The deadline for initial proposal submission is November 15th, after which a panel of recycling industry experts will select the top ten teams to go on as finalists. The finalists will get to build working prototypes and showcase them at a live event in June.

In order to make it to the final level, teams should include a viable plan for the final product, which includes the following:

Project description that identifies the problem and how the proposal will address it
Technical approach that describes how the solution works and will be built and implemented
Budget estimate and list of materials and equipment needed to build the solution
Expected timeline for how long it will take to develop the initial project iteration
Breakdown of economic viability, including how much it costs to produce the solution

In addition, because PLA has several limitations, such as needing special precautions so it is food-safe, participants should clearly explain how they will address these challenges.

The teams will be judged on criteria such as feasibility, impact, novelty, how they address material limitations, and overall presentation. In addition, while there is technically no challenge budget for teams, proposals will be judged, at least in part, on their resourcefulness.

“The best solutions may not be the ones that require the most expensive equipment,” Print Your Mind 3D warns in the Frequently Asked Questions section of the challenge.

The grand prize will be a new Ultimaker 2+ 3D printer, which will come with the Ultimaker app, swappable 0.25, 0.4, 0.6 and 0.8 mm nozzles, a 0.75 kg spool of silver PLA filament, Cura print preparation software, a calibration card for build plate leveling, a 12-month warranty, and lifetime support from Print Your Mind 3D, in addition to items like a USB cable and glue stick. Additional prizes will be announced in the coming weeks.

To register a high school team for the new Print Your Mind 3D PLA Recycling Challenge, visit the challenge website.

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Filaments.ca releases fully food safe PLA for 3D printers

Filaments.ca, a prominent Canadian webstore for 3D printer materials, has released a new fully food safe filament range unlocking the potential of kitchen-friendly 3D printing projects. True Food Safe PLA (True FS PLA) is now available to order exclusively from the site (filaments.ca), and can be used to 3D print cups, cutlery, cookie cutters, utensils, […]

Comparing FDM 3D Printed Parts with Carbon Nanotubes, Continuous Carbon Fiber and Short Carbon Fiber

Fused deposition modeling, or FDM, 3D printing has several advantages – thermoplastics can be used, which are easy to handle and are strong and durable enough to be used for producing both prototypes and practical parts. Additionally, FDM 3D printers use a simple mechanism to melt and extrude resin that doesn’t need expensive parts, like lasers, which makes the machines less expensive. But, the technology does not always provide enough strength for mechanical parts.

That’s why additional materials with good mechanical properties, such as carbon nanotubes (CNT) and fiber reinforced composites, are often added to improve strength; depending on the length, carbon fiber can also be divided up into both short and continuous fiber. A group of researchers from Doshisha University and Kyoraku Co., Ltd., both in Japan, recently published a study, titled “Comparison of strength of 3D printing objects using short fiber and continuous long fiber,” that compared the usefulness and strength of objects 3D printed with short carbon fiber, continuous carbon fiber, and multi-wall carbon nanotube (MWCNT).

The abstract reads, “In this research, composite materials were used to improve the strength of FDM 3D printed objects. The nanocomposites made from polylactic acid as matrix and multi-wall carbon nanotube as filler, short carbon fiber reinforced composite and continuous carbon fiber reinforced composite were prepared, and tensile test was carried out. As a result, the continuous fiber reinforced material exhibited tensile strength of about 7 times and elastic modulus about 5 times that of the other two materials. The strength was greatly improved by using the continuous fiber. The fracture surface after the test was observed using a scanning electron microscope. The result of observation shows that adhesion between the laminated layers and the relationship between the fiber and the matrix are bad, and improving these are necessary to increase strength. Comparing those materials, it is possible to improve the strength in some degree by using short fiber while maintaining ease of printing. On the other hand, by using continuous fiber it can be achieved significant strength improvement while printing was complicated.”

The fracture surface of PLA/MWCNT

To make their PLA/MWCNT nanocomposite, the researchers used polylactic material as a matrix, with MWCNT as a filler, and formed the material into a 1.75 mm filament. They used commercial ONYX, carbon fiber, and NYLON materials from Markforged to 3D print tensile test pieces from continuous carbon fiber reinforced thermoplastic (continuous CFRTP) and short carbon fiber reinforced thermoplastic (short CFRTP).

“The specimen shape is different due to the limitation by the performance of the 3D printer,” the researchers wrote in the paper. “For PLA/MWCNT, smaller one was chosen to avoid warp and print quickly. The PLA/MWCNT has three outer walls and fills inside alternately at 45 degrees and -45 degrees.”

For the continuous CFRTP, carbon fibers oriented in the load direction were 3D printed in the center, while the outside was covered with either neat resin or short fiber reinforced composite; this last was used to 3D print the short CFRTP in the same manner as the PLA composite had been fabricate.

The researchers completed a tensile test on the pieces, and used a scanning electron microscope to observe images of the specimen’s fracture surface. They also looked at their stress and strain.

“In PLA/MWCNT, the stress increased almost linearly until fracture,” the paper explained. “The breaking strain was about 1 ~ 2%, and no stress reduction was occurred. Compared with neat PLA, the elastic modulus was not greatly improved but the tensile strength was improved and increased by 48% when 1wt% of MWCNT is added. In that case, the tensile strength was 53 MPa and the Young’s modulus was 3 GPa. Until 1 wt%, the tensile strength was improved as more CNT is added, but strength was decreased when 3wt% was added. It is because the aggregation of MWCNT. The aggregations are considered to act as internal defects of the material.”

Aggregates and voids

When more MWCNT was added, the number of aggregates increased. The researchers found that the relationship between the fiber and the matrix, along with adhesion between the laminated layers, was not good – when these are improved, the strength will increase. Significant strength improvements can be achieved by using continuous fiber, but the 3D printing process is complicated, and it’s necessary to use modified equipment, such as a special nozzle. But short fiber is easier to print, and still offers some degree of improved strength.

“The short CFRTP and PLA/MWCNT are inferior in mechanical properties compared to the continuous. But they can be printed with conventional 3D printers without special modifying,” the researchers explained. “Especially the nanocomposites demonstrate its effect by adding a small amount. The mass concentration of fiber was 35.7 wt% for continuous CFRTP and 14.3 wt% for short CFRTP, but MWCNT was 3wt% or less. Generally, the smaller the amount of reinforcement, the more easy to print. In fact the PLA/MWCNT nanocomposite can be printed with commercially available 3D printer without special modified in this study. Continuous fiber and short fiber material should each have merits and demerits and should be used properly.”

The broken specimen (continuous CFRTP)

Co-authors of the paper are T. Isobe, T. Tanaka, T. Nomura, and R. Yuasa.

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Review: Amazon Basics 3D printer filament PLA and PETG

Recently, leading online marketplace Amazon sparked the 3D printing rumor-mill with the launch of its own brand Basics FFF/FDM filament. To investigate the new materials range ourselves, 3D Printing Industry ordered two spools of the filament. In this review the print quality of Amazon Basics Black PLA and Red PETG are examined using standard parameters […]

Amazon now selling own-brand 3D printer filament

Leading eCommerce platform Amazon has launched its own brand of 3D printer filaments available for global sale and delivery. While current wait time for the products is listed as 1 – 3 months, the move is interesting as the filaments are available in the AmazonBasics range – putting them in line with common household essentials such […]

Student Creates CUDA, the 3D Printed Underwater Jet Pack

About 71% of the Earth’s surface is covered with water and while technology for traveling on dry land has developed that allows people of moderate income to cover a fair amount of ground relatively quickly, underwater exploration of a comparable sort has remained out of reach for all but a few. In terms of individual exploration, the ‘luxury seatoy’ SEABOB underwater scooter has infiltrated the dreams of those interested in underwater transport — but with a price tag of about $17,000 it will remain a dream for most. In response to the inaccessibility of this kind of technology, one young man decided he was going to work to create a more price-friendly alternative.

This innovative young man, Archie O’Brien, worked with 3D Hubs to create his underwater enhanced transportation device, which he has named the CUDA. O’Brien’s creation won him first place in the recently announced 2018 3D Hubs Student Grant program in the Product Design category.

The CUDA is a jet propulsion-driven backpack which the user wears allowing a hands-free jet pack experience underwater. The initial idea was to miniaturize a jet ski and utilize that, but it didn’t quite fit in the backpack configuration. After a careful reading of “Numerical Analysis of a Waterjet Propulsion System” by Norbert Willem Herman Bulten, O’Brien was convinced that despite the difficulties involved, he could come up with something that would be better suited to the backpack configuration.

With dreams of gliding effortlessly through the clear waters off of Iceland or as a member of a pod of dolphins, he set out to experiment and research and experiment again. In order to be able to quickly create and rapidly iterate while developing the jet pack, O’Brien utilized 3D printing and CNC technologies. This also allowed him to control for costs as it was part of his primary objective to create something that could be significantly more affordable than anything else on the market. As such, he used FDM technology and PLA, two of the most widely accessible and economically viable methods for fabricating. In addition, SLS was used to create the impeller, using carbon fiber infused powder which gave extreme stiffness needed for such parts.

The key test was determining how the 45 3D printed parts would hold up underwater. To prepare them to operate in such extreme conditions, all the 3D printed parts were first coated with a thin layer of epoxy resin that was then slow-dried, and silicone seals were added to all of the access doors in order to keep water from leaking in and shorting out the battery and other electronics.

But, of course, the proof of the pudding is in the eating, and so there was nothing else to do but throw the thing on and get in the water, which O’Brien has done with gusto, testing the CUDA out in both pools and open water. In addition, parts have been left in water for months to see if they can withstand prolonged exposure, and so far it has all been up to snuff. The CUDA itself requires only 10 minutes to assemble – though I’m assuming that’s for someone with experience if my history of IKEA assembly finish times are any indicator. Once assembly is complete, the backpack is designed to work intuitively, with its harness holding it at 90 degrees in relation to your shoulders and speed controlled by a handheld trigger.

The CUDA is currently patent pending with hopes for the first commercially available models to hit the market in 2019.

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[Source/Images: 3D Hubs]

Introducing CUDA: the 3D printed underwater jetpack

Archie O’Brien is a design student at Loughborough University. For his final project, in collaboration with service bureau 3D Hubs, O’Brien has applied 3D printing to the creation of a novel, patent-pending jetpack for underwater exploration. Look out Aquaman… How it’s made O’Brien’s smooth underwater jetpack is called CUDA, and was created in response to heavy and […]