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3DPrint.com Review of the Creality CR-6 SE

I received a pre-production version of the Creality CR-6 SE 3D printer for review a few weeks ago. I’m pleasantly surprised with this solid printer which is currently on Kickstarter for $339 and will be $429 later. It’s a step up from earlier Creality offerings, is relatively easy to use, and dependable. It’s a value for money machine that is an improved version of an Ender with some better components. Safety features, an improved extruder, and a better feeder make this a better printer, suited for beginners and everyday use.

Specs

235 by 235 by 250mm build volume.
Auto-leveling
Filament end detection
Touch screen
Mini USB/SD Card
Carborundum glass bed

Unboxing

Unboxing the CR-6 was easy and the most difficult thing was the manual. I also didn’t know about the handy little tool drawer beforehand but actually that is quite handy once I managed to find it. The toolset is alright with the little pliers being very handy indeed. I had the printer set up and printing within 15 minutes of unpacking it. One of the only parts where you have to pay attention is in placing the Z stage correctly, so just take some time to make sure that this is perpendicular and that it is placed absolutely level. The other part where you have to pay attention is when placing the main plug on the front of the printer the right way.

Software

I had to update the firmware and the Creality software worked well for the printer. I also tried just regular Cura with a modified Ender profile and this worked well also. I did some prints with Slic3r and this was fine as well. The Creality software is relatively easy to use and easy for beginners as well. There were some issues with saving to the SD cards with my own SD cards not working and certain file names being too long or having exotic characters and not working either. The workarounds were to format my SD cards and to shorten the file names.

Touchscreen

I had some issues with the touchscreen crashing but this was due to me having a preproduction version and was fixed. Other than that, the touchscreen works well and is super simple to use every day. Menus that you need are very accessible. Part of me wanted more accessible tuning options but that would make it more complex to understand.

Leveling & Filament End Detection

Bed leveling worked like a dream on the printer and was super easy. Filament end detection and pausing prints worked as well. I also ripped out filament and the software paused the print and let me feed new filament back in again. These features are all very handy and work well.

Carborundum glass build plate

This part really threw me. The first week I totally completely loved the build plate which is a coated glass plate that works like a dream for PLA. I tried several PLA variants and they all worked well. After intensive use however, there were some adhesion issues especially with prints that had little initial surface area. I found it more difficult to clean this plate compared to regular glass also. I had real issues with the adhesion of ASA, ABS and PETG variant materials on the build plate. I’d recommend another build surface if you’d like to vary your materials. If you don’t damage the plate it works wonderfully with PLA though, so do be careful when removing prints.

Chassis

The aluminum extruded profile chassis of the printer with the power supply in it makes for a solid base and reduces vibrations and misprints when compared to other similar printers. On the whole, components are more well made than we expect in this price category. Machining and finishing was, on the whole, better than comparable printers as well.

General operation

It’s a simple system to use and general maintenance stuff such as belt tensioning, leveling, and printing is straightforward. Compared to similarly priced systems it is quiet and just pumps out print after print in PLA. You can hear the fans work but little else. After my testing, I started making dozens of ear savers for friends and acquaintances and it just kept on working well. For PLA it’s a dream at this price point. Feeding in filament was easy as was removing it. I found that for me it worked better with an external spool holder.

Prints

Prints for PLA were good with the default settings and default operation working well. The printer was reliable and gave a good surface finish straight out of the box. Small tweaks improved this so that one could reliably make PLA prints that looked good.

Opinion

This is a surprisingly solid 3D printer for the price. For entry-level systems this is a step forward in ease of use, components, the chassis, and in general operation. All of the leveling and day to day operation features work well. Both the feeder and nozzle are significant steps up from previous Creality designs. For PLA it works well but with the standard build platform, ABS and other materials are just not possible. Also, I’m not sold on the longevity of the coating on the platform either. This can be remedied through a BuildTak or other build plate though. All in all this is a good printer that offers a lot of value for money for the price.

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Is This the Best Way to Manually Post-Process an FDM 3D Printed Part?

Researchers Jinjin Liu, Hai Gu, Bin Li, Lu Zhu, Jie Jiang, and Jie Zhang from the Nantong Institute of Technology and Jiangsu Key Laboratory of 3D Printing Equipment and Application published a paper, titled “Research on Artificial Post-Treatment Technology of FDM Forming Parts,’ about using manual post-processing on 3D printed parts made with FDM technology, which has a low molding accuracy that can cause stair-stepping.

“Due to the “step effect”, the printed parts have rough surface, obvious stripes, poor surface quality, and cannot meet the customer’s or specified requirements, so post-processing is very important. This paper mainly studies and summarizes the manual post-processing technology of FDM printed parts, and provides the specific implementation method of post-processing, providing reference for the post-processing of FDM formed parts and other forming processes,” the researchers wrote.

Figure 2. The vase model.

In order to “further improve the surface quality and strength” of 3D printed models, post-processing is often necessary. Some of the more common methods of post-processing FDM formed parts include:

Chemical treatment with organic solvent
Heat treatment
Mechanical treatment with a sander or grinder
Surface coating treatment

In this paper, the researchers focused on a manual post-treatment process, which requires several items to work properly, such as a spray pen air pump with air storage tank, a coloring pen and tool set, gloves, a mask, water-diluted solvent in a solvent bottle, quick dry small fill soil, 80 to 3000 mesh sandpaper, a cleaning agent, a file, and others.

The team fabricated a post-treatment vase model as an example, using PLA material and an Einstart 3D printer. Once the vase was printed, they removed the plate with the model on it from the printer.

Figure 4. Model finished printing. Figure 5. Demolition of support.

“…the model is smoothly removed from the bottom plate with a shovel, and then to check whether there is strain concentration model, relatively weak parts with small first stripping knife to spin out the model and the support, and then has a long nose pliers clamping a direction support, applying a constant force, the location of the tiny support can use the file to remove,” they wrote.

To clean up a rough surface, the researchers noted that you can use low mesh sandpaper to sand and polish it. The model and the low mesh sandpaper should be immersed in water and sanded along the model’s texture, as this can both extend the sandpaper’s life and smooth out the model’s surface.

Then, they moved on to a technique called quick dry small fill, which involves the addition of a small amount of filling material to gaps in the model; then, the fill is evenly daubed with a hard scraper.

Figure 7. Apply small patch of soil evenly. Figure 8. Polished to make it smooth.

“Then wait for 30 seconds, after filling soil has hardened, using 1200 mesh to 1500 mesh sandpaper in, as shown in figure 8, If there are still tiny grooves and repeat the above steps,” the researchers wrote. “To be in addition to the groove after no large-area fill soil, feel smooth, can proceed to the next step.”

The next step is spray can water fill soil spraying. First, the model’s surface should be washed with water, and then the spray pot is used to fill the soil, before the model is wiped with a non-woven cloth and sprayed at “the ventilated position,” keeping the nozzle at about 20 cm and uniformly spraying the model one to three times, quickly.

“Generally, choose gray spray pot water to fill the soil, because gray is a neutral color,” the team explained.

Figure 10. High mesh sandpaper grinding.

Once the water is sprayed and the soil is filled, air drying takes place. Then, 2000-3000 high-mesh sandpaper is applied for “slight grinding” along one direction, before moving on to the coloring phase.

The 3D printed, polished and processed model should first be washed and dried before pigments are applied. A spray gun can be used to add either a base color or one that covers a large area of the model; you’ll need a 1:2 ratio of diluent to pigment for spraying, and you should be able to adjust the amount of air injection while you’re spraying.

“Brushes of different thicknesses and sizes can be used to paint the details,” the team wrote. “It is accessible to use 00000 pens to paint the detailed parts of the figures, or use different widths of the cover tape to cover and then spray the spray gun to paint.”

Once the paint and spray paint have dried completely, you can uniformly spray protective paint on the model; the research team used B603 water-based extinction for their 3D printed vase.

The team shared a few more notes on making the post-treatment process run smoothly, such as the importance of using software to reduce the amount of unnecessary support structures, coating the print plate with a thin layer of glue to prevent deformation, and observing the model while it’s being printed.

Figure 13. The vase is finished after processing.

“Secondly, in the manual post-processing should look to the protection work, grinding water mill is the best way to model processing, be patient, 80-2500 mesh, use each mesh sandpaper required time from long to short, low mesh sandpaper grinding along the texture of the model, high mesh sandpaper grinding should be turned around,” the researchers concluded. “When mixing colors, you should understand in advance the relationship between light and shade, brightness and purity of various colors, warm and cold color selection, etc.”

They noted that “the degree of difficulty” for post-processing methods, and the methods themselves, can vary with different 3D printing technologies – what works for FDM may not necessarily work for SLA, and so on.

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McGill University Researchers: Can We Use PLA for Desktop Bioprinting?

Bioprinting has proven to be useful for bone regeneration, as researchers learn to create more stable structures that mimic human tissue. In ‘Three-Dimensional Printed Polylactic Acid Scaffolds Promote Bonelike Matrix Deposition in Vitro,’ authors Rayan Fairag, Derek H. Rosenzweig, Jose L. Ramirez-Garcialuna, Michael H. Weber, and Lisbet Haglund explore the uses of desktop bioprinting with PLA.

Even in conventional medicine today, surgeons find difficulty in repairing bones that have undergone trauma, whether due to an accident, tumor, or other serious issue. Grafting can still be challenging to complete, and then problematic later in terms of pain, infection, and the need for multiple procedures. Materials such as calcium phosphate bone cement (a synthetic graft) have become more popular for repairing bone defects, but there are also limitations due to lack of mechanical strength. While poly-cements have been used also, they can cause stress around the ‘target area,’ and lead to secondary fracture, which defeats the purpose of healing altogether.

Here, the researchers have investigated the use of tissue engineering for bone repair in growing cells, scaffolds, and using numerous bioactive factors. 3D printing has been successful in fabricating scaffolds using different polymers like PLA.

“The ideal material for scaffold development should fulfill specific criteria,” state the researchers. “The material must be biocompatible and must be capable of being generated with an interconnected network to mimic the natural tissue architecture.”

Cell sustainability is the greatest challenge, along with creating stable structures. The researchers sought to create scaffolds that would allow for complete cell sustainability, along with the best environment for encouraging tissue to form. They must also allow for the following:

Fabrication in different, complex shapes
Resistance to inflammation and toxicity
Strong mechanical properties
Appropriate porosity
Affordability

In previous studies, the researchers were aware that PLA 3D printed from the desktop was suitable for both chondrocyte and nucleus pulposus tissue engineering applications. Here, they tested PLA scaffolds with pore sizes of 500, 750, and 1000 μm, fabricating accurate structures with good porosity; in fact, all scaffolds reflected pores in line with the initial designs, leaving the authors to conclude that this ‘suggested accuracy’ with desktop 3D printer—in this case, the Flashforge Creator Pro.

Pore size results were as follows:

Small pore scaffolds – 585.61 μm ± 26.40
Medium pore scaffolds – 769.94 μm ± 12.98
Large pore scaffolds – 1028.85 μm ± 57.54, p < 0.0001

“The scaffold fabrication and replication process manifests high accuracy and precision as evidenced by μCT analysis, which proves the value of low-cost printing in tissue engineering applications,” stated the researchers.

The authors reported the following for mechanical properties:

“Significant differences in stiffness were observed between the three sizes (p < 0.05, p < 0.0001) in which Young’s modulus for the small pore size was 206.7 MPa ± 0.17 SD, medium size scaffold was 137.5 MPa ± 6.98 SD, and 116.4 MPa ± 5.97 SD for the large size PLA scaffold.”

Mechanical properties of 3D-printed scaffolds. (A) Young’s modulus representing 5−10% compressive stress/strain curves of printed PLA scaffolds. For each set, (n = 3), error bars represent ±SD and (* = P value < 0.05), (# = P value < 0.0001). (B) Stress/strain curves of 500, 750, and 1000 μm showing the amount of deformation, elastic (proportionality) limit, and plastic region. For each set, (n = 3).

“The failure point of each scaffold was determined from the stress/strain curves in which the small-size failure point was around 21.63 MPa, around 11.86 MPa for the medium size, and around 8.53 MPa for the large-pore scaffold. Our results demonstrated an overall higher compressive modulus with smaller pores because of the addition of bulk material (smallest pore size has the highest amount of material and is the stiffest).”

The use of PLA was successful, indicating both accuracy and reproducibility, and the scaffolds presented properties like native bone. The authors stated that the data reflected structures stable enough for an environment recruiting host stem cells and repairing bone.

Morphological characterization of 3D printed scaffolds. (A) Representative images of the 3D models with dimensions and printing process. (B) Quantification of scaffold weight, (n = 6), error bars represent ±SD (** = P value < 0.005), (# = P value < 0.0001), with a representative image of printed scaffolds (Canon EOS 350d Camera). (C) Pore size was calculated by scanning electron microscopy, and porosity was determined by μ-CT. For each set, (n = 3), error bars represent ±SD and (* = P value < 0.05), (** = P value < 0.005), (# = P value < 0.0001).

“In vivo studies will be necessary to determine potential adverse effects, bone repair, and scaffold resorption rates,” stated the researchers. “It comes without surprise that 3D printing has been strongly adopted by orthopedic surgery clinical practice, medical education, patient education, and orthopedic-related basic science.

“Whereas 3D printing has been used for some time to generate patient models of defects for presurgical planning, there is a growing shift in using this technology in actual bone or tissue repair. One major focus in orthopedic and reconstructive surgery is to use 3D printed constructs for filling bone defects, substituting current standard therapies as an innovative approach for bone repair. Several studies have shown applicability and clinical relevance of using different types of 3D-printed polymers as a graft substitute.”

From 3D printing in hospitals to bioprinting in outer space and bringing forth materials which may eventually yield fabricated human organs, researchers are driven to create what used to be considered impossible, with a wide range of innovations already in use around the world. Find out more about desktop bioprinting here. What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.

SEM of acellular and cell-seeded scaffolds. Representative SEM images of acellular, osteoblasts, MSC−OST seeded scaffolds at 80×,450×,1500×, and 22 000× magnifications and scale bars represent 1 mm, 200, 50, and 5 μm with the rectangular marker indicating the region of the scan (n = 3).

[Source / Images: ‘3D-Printed Polylactic Acid (PLA) Scaffolds Promote Bone-like Matrix Deposition In-vitro’]

Researchers Investigate Tensile Properties of 3D Printed PLA Specimens: Is 80% Infill Best?

Comparison between 3D printed products from both recycled and virgin PLA.

Plastic is still one of the most popular, least expensive 3D printing materials, and polylactic acid, better known as PLA, is at the top of the bunch, due to its high strength, biocompatibility, and biodegradable nature. A lot of studies have been completed regarding PLA 3D printing filament, and a team of researchers from the Universiti Malaysia Pahang (UMP) recently published a paper, titled “Preliminary investigations of polylactic acid (PLA) properties,” that details their investigation of the tensile property of a PLA specimen 3D printed using FDM technology, along with figuring out the optimum combination of 3D printing parameters to achieve maximum mechanical properties.

The abstract reads, “This research work aims to investigate the tensile property of Polylactic Acid (PLA) and to determine optimum printing parameter combinations with the aim of acquiring maximum response using low-cost fused filament printer. Two parameters chosen to be varied in this research are raster angle and infill density, with the value of 20°, 40°, 60° and 20%, 50%, 80% respectively. Tensile specimens with a combination of these two parameters were printed according to ASTM D638 type 1 standard. Three mechanical properties were analysed, namely ultimate tensile strength, elastic modulus and yield strength. It was found that the tensile property increases with the infill density. Meanwhile, both high and low raster angle have shown the considerably high mechanical properties. The optimum parameters combination is 40° raster angle, and 80% infill density. Its optimum mechanical property is 32.938 MPa for ultimate tensile strength, 807.489 MPa for elastic modulus and 26.082 MPa for yield strength.”

Applications for FDM 3D printing include more load-bearing parts for specific requirements, and many of these demand a “certain level of mechanical property information” to be set as a benchmark in order to assess a 3D printed PLA part’s strength.

This strength typically relies on some specific 3D printing parameters, including layer height, infill density, and raster angle, which refers to the direction of the beads of material in regards to loading of a part or component. In the experiment, several parameters were kept constant in order to “avoid mislead of result obtained.”

“The design of the experiment includes the parameter and its value selected to be investigated,” the researchers wrote. “Two chosen parameters are raster angle and infill density, with a value of 40°, 60°, 80° and 20%, 50%, 80% respectively. Layer height is kept constant at 0.1 mm throughout this whole experiment. The total number of parameter combinations are 9. Since the sample size is 5, the total number of specimens printed are 45 specimens.”

While the layer height remained 0.1 mm for each of the nine parameter combinations, the raster angle was split up into three groups: three at 40°, three at 60°, and three at 80°. The three infill densities tested were 20%, 50%, and 80%. The team used a Rainstorm Desktop 2D Multicolor Printing Printer Reprap Prusa i3, with 0.4 mm nozzle, to manufacture the tensile test specimen out of 1.75 mm PLA, which was designed using SOLIDWORKS and sliced with Repetier Host software.

Average stress strain curve for all 9 parameter combinations.

The team completed tensile testing, with a maximum load of 50 kN, on all nine of the 3D printed, 3.2 mm thick PLA specimens at a speed of 5 mm/min, according to ASTM D638 standard. The ultimate tensile strength, yield strength, and elastic modulus were extracted from multiple regions and points: proportional limit, elastic limit, yield point, ultimate stress point, and fracture point.

“Ultimate tensile strength (UTS) is the maximum stress that a material can withstand without undergoing plastic deformation while being stretched or pulled,” the researchers explained. “Elastic modulus is the ratio of the force exerted upon a substance to the resultant deformation it experiences, or also known as stiffness. Meanwhile, yield strength is the stress required to produce a small specified amount of plastic deformation.”

The team discovered that when the infill increased, so too did all the property values, which means it’s possible to choose the right infill percentage in order to achieve economic material use.

“Upon analysis of all obtained data, the best-suited parameter combination that results in optimum mechanical property have been identified, which is 3rd parameter combination of 40° raster angle and 80% infill density,” the researchers noted. “It has resulted in the ultimate tensile strength of 32.938 MPa, elastic modulus of 807.489 MPa and yield strength of 26.082 MPa. The 9th combination was not chosen as the optimum parameter condition due to its lower yield strength comparatively. Selection of optimum parameter combination was made based on the criteria of possible maximum mechanical property.”

(a) Fabricated PLA tensile specimen, (b) working mechanism of FDM

The researchers did not investigate the effect of infill density or raster angle on the specimen’s UTS, yield strength, or elastic modulus for this paper.

“The tensile properties of PLA 3D printed specimens were successfully extracted from the plotted stress-strain graphs upon tensile tests. From the obtained experimental data, the optimum parameter combination with the maximum mechanical property was determined. However, these research results are not adequate for 3D printer user to explore the options they have based on their specific need,” the researchers concluded. “Therefore, this scope of research must be extended by including more ranges of parameter values to be investigated.”

Co-authors of the paper are S. R. Subramaniam, M. Samykano, S. K. Selvamani, W. K. Ngui, K. Kadirgama, K. Sudhakar, and M. S. Idris.

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Comparing the Operational Characteristics of Plastic 3D Printed Spur Gears

Back to back gear test rig used in performed experimental research.

Spur gears, which can achieve high transmission ratio and energy efficiency, are comment elements used in the transmission of motion and high intensity power for mechanical power drives, i.e. belt drives, chain drives, and cylindrical gear drives. These power transmission elements are exposed to non-conforming operating conditions in terms of load and speed, and are also applicable at high speeds. Spur gears play a big role in mechanical engineering, and are often tested in back to back gear test rigs in order to gain data regarding the gear teeth flanks’ surface load capacity.

A group of researchers from the University of Belgrade in Serbia and the Slovak University of Technology in Bratislava published a paper, titled “The Influence of Material on the Operational Characteristics of Spur Gears Manufactured by the 3D Printing Technology,” on their efforts to test plastic 3D printed spur gears on a back to back gear test rig, in order to increase the use of the technology in manufacturing these gears.

3D printing direction of the 3D printed spur gear.

“In this paper the influence of the material type on the operational characteristics of spur gears manufactured by the 3D printing technology is analyzed, after the experimental testing performed on a back to back gear test rig, in the predefined laboratory conditions,” the researchers wrote.

“For the purposes of this paper, two types of polymeric materials were analyzed. The initial load in the form of a torque that was exposed to the spur gears was held constant, while the number of revolutions per minute of spur gears was varied. The plastic gears tested in this experiment operated in unlubricated working conditions.”

The researchers performed a comparative analysis, using commercially available PLA and ABS materials, on their impact on the 3D printed spur gears’ operating performance. The most common bulk failures in spur gears made of metal are teeth fractures and surface degradation like pitting and scuffing, but the researchers weren’t quite sure if this would be the case for their 3D printed plastic gears.

“With metallic spur gears, the load in the form of torque increases at the appropriate levels while simultaneously controlling the process of surface destruction of the gear teeth flanks,” the researchers explained.

“For the purposes of this experiment, the load in the form of a torque is fixed, that is, the initial moment of constant intensity has value 20 Nm. The torque of this intensity is insufficient to cause premature surface and volume destruction of spur gear teeth. The initially captured torque is “lost” during the wear process. The idea of this experiment was to estimate the wearing intensity for the initially captured load for two different spur gear materials.”

Worn off teeth flank surfaces of the tested PLA gears.

While back to back gear testing typically includes a constant number of revolutions of the electric motor, the frequency regulator was connected to the electric motor for this testing in order to have the ability to change the rotation. The researchers adopted a rotational speed change of 200 rpm, which was changed every ten minutes during the experiment, meaning they reached the maximum 1400 rpm after an hour of testing.

Indicators most commonly used for spur gear operational analysis include temperatures, noise and vibration levels, and the quantity and shape of wear products, and the researchers chose vibration (RMS acceleration) and temperature as the main indicators for their 3D printed ones. A thermal imaging camera was used to record the meshing temperature field of the 3D printed spur gears, while an SKF Microlog Analyzer GX collected information on the vibrations.

“Knowing the number of teeth of the tested spur gears, as well as their number of revolutions, a change in the amplitude of the vibration level is observed over time, by distinguishing the peak resulting from the meshing of the plastic spur gears,” the researchers explained.

In the first five minutes of the experiment under 200 rpm, there was hardly any vibration observed; additionally, in the first ten minutes under 200 rpm, the temperature of the PLA gears was about 20% higher than that of the ABS gears. Eventually, the 3D printed ABS spur gears endured roughly 30 minutes of work before experiencing failure in their teeth at 600 rpm, while the 3D printed PLA spur gears lasted for 90 minutes at 1400 rpm with no visible fractures, but showing “evident teeth contact surface destruction.”

Failure at the teeth roots of the tested ABS gears.

“In the interval from 5 to 15 minutes, vibrations behaviour of ABS and PLA plastic gear pairs is inverse comparing to their thermal behaviour,” the researchers wrote. “The vibrations of ABS plastic gears is higher (RMS=0,18 ms-2) than the ones made of PLA plastic (RMS=0,06 ms-2). Increasing the rotational speed from 300 up the 400 rpm, the vibration of both gear pairs significantly rises (up to RMS=0,72 ms-2). After 400 to 500 and 600 rpm, the vibration levels are declining. After 30 minutes of testing with 600 rpm, just before tooth of ABS gear pair fractured, the level of RMS accelerations was 0,3 ms-2. The vibration level of PLA plastic gear pair vary with an increase of rpm and oscillate around 0,25 ms-2. At the end of experiment (on 1400 rpm) the vibration values of PLA plastic gear pair is increasing to 0,5 ms-2, probably due to gear tooth contact surface destruction.”

Based on their findings, the researchers were able to conclude that the 3D printed PLA spur gears had better operational characteristics than the ABS ones.

Co-authors of the paper are Aleksandar Dimić, Žarko Mišković, Radivoje Mitrović, Mileta Ristivojević, Zoran Stamenić, Ján Danko, Jozef Bucha, and Tomáš Milesich.

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Researchers Study Effects of Layer Thickness on 3D Printed PLA Samples

(a) Layer thickness and perimeter raster, (b) illustration of 3D printing orientations

A group of researchers from the National Institute of Aeronautics and Space (LAPAN) in Indonesia worked on the mechanical characterization (flexural properties) of biodegradable PLA materials produced by extrusion-based 3D printing methods (FDM, Fused Deposition Modeling, FFF). Plenty of research has been done on various 3D printing parameters, and this research team chose to focus on the effect of various layer thicknesses of 3D printed PLA on flexural properties in their new paper, titled “Effect of layer thickness of flexural properties of PLA (PolyLactid Acid) by 3D printing.”

The abstract reads, “The study begins from manufacture the solid 3D model based on the ASTM standards for flexural properties test of the material using Three-point bending method. Three-point bending test was conducted with Tensilon Universal Testing Machine – AND RTF-2410 with a 100kN load cell, specimen shape and size according to standard size ASTM D 790. The result shown that the layer thickness had an effect on flexural strengths of PLA samples. The maximum flexural strengths from Lt = 0.4 to 0.5mm were significantly increase. Moreover, it is worth nothing that ductility decreased as layer thickness increased. According to test result that the maximum flexural strength occurred at 0.5 mm layer thickness with 59.6 MPa and the minimum flexural strength occurred at 0.1 mm layer thickness with 43.6 MPa. The higher layer thickness tended to promote higher strength. The thicker layer is the stronger layer bond in holding the load bending. In this study the thicker layer have tendend to shown a 90-degree delamination fracture and the thinner layer have tendend to shown a 45-degree delamination fracture according to the direction of printing is ± 45°.”

The team quoted other researchers in noting that while “layer thickness has been studied extensively, it should be further analyzed” because of the disparity of the results regarding features like tensile strength and flexural strength.

“The objectives of this research is to know the influence of layer thickness {0.1, 0.2, 0.3, 0.4, 0.5} mm on flexurel properties of PolyLactid Acid (PLA) 3D printing,” the researchers wrote.

The researchers set out to analyze the flexural performance of samples 3D printed out of commercial 1.75 mm PLA filament on a desktop FDM50-5050 3D printer by ZBOT.CC. Three-point bending tests were conducted to determine the 3D printed samples’ flexural response in terms of strength and stiffness.

“In this study, a solid sample was filled with a raster perimeter analyzed, in which the tool path was offset from the perimeter with a distance equivalent to the nozzle size,” the researchers explained.

The results show that the PLA materials’ flexural strength was in fact significantly affected by the layer thickness of the 3D printed samples.

Three-point bending test

“Layer thickness is directly related to the number of layers needed to print a part and hence to printing time,” the researchers wrote.

“Each specimen has the same thickness of 4mm, but the layer thickness of the specimen is different from {0.1, 0.2, 0.3, 0.4 and 0.5}mm to get a thickness of 4mm. The load maximum received by the specimen is different for each specimen so that the value of the flexural strength is also different. The effect of layer thickness on the flexurel properties was different for each sample. In this case, higher layer thickness tended to promote higher strength. These results were in accordance with previous works with PLA.”

Fracture characteristics of PLA samples with different layer thickness: (a) 0.1mm, (b) 0.2mm, (c) 0.3mm, (d) 0.4mm, (e) 0.5mm.

Their results showed that, in terms of upright orientation, flexural and tensile strengths both increased as the layer thickness increased, and that the higher the layer thickness, the higher the strength.

“The thicker layer is the stronger layer bond in holding the load bending,” the researchers concluded. “In this study the thicker layer have tendend to shown a 90-degree delamination fracture and the thinner layer have tendend to shown a 45- degree delamination fracture according to the direction of printing is ± 45°.”

In the future, the researchers plan to study the effects of build orientation, feed rate, and tool patch on the mechanical properties of 3D printed parts.

Co-authors of the paper are A. Nugroho, R. Ardiansyah, L. Rusita and I. L. Larasati.

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Researchers Demonstrate Wideband Metamaterial Absorber Made of 3D Printed Conductive Plastic

Architecture of the wideband MA

There’s been a lot of research into 3D printing metamaterials over the years – due to their unique properties, they’ve been used to make everything from headphones and heart valve models to door locks and acoustic holograms, and maybe someday even our very own invisibility cloaks. But ten years ago, the metamaterial absorber (MA), a type of metamaterial with compact size and thin configuration meant to efficiently absorb electromagnetic radiation, was presented for the first time. Since that time, there have been numerous other MAs, including dual-, triple-, and multiband varieties and the wideband MA.

Because of its high absorption, wideband MAs are highly sought after for applications in sensing, nondestructive detection, and imaging. There are a few ways to increase the absorption bandwidth for wideband MAs, but it’s still tough to manufacture them.

Unit cell of the MA: (a) perspective; (b) layout

A collaborative team of researchers from China’s Hefei University of Technology, the Beijing University of Chemical Technology, and Space Star Technology Co. Ltd. recently published a paper, titled “Wideband Metamaterial Absorbers Based on Conductive Plastic with Additive Manufacturing Technology,” that explains their development of a wideband MA based on 3D printed conductive plastic.

They believe that their new method is the first ever demonstration of a 3D printed wideband MA.

The abstract reads, “This paper proposes a wideband and polarization-insensitive metamaterial absorber (MA) based on tractable conductive plastic, which is compatible with an additive manufacturing technology. We provide the design, fabrication, and measurement result of the proposed absorber and investigate its absorption principle. The performance characteristics of the structure are demonstrated numerically and experimentally. The simulation results indicate that the absorption of this absorber is greater than 90% in the frequency range of 16.3−54.3 GHz, corresponding to the relative absorption bandwidth of 108%, where a high absorption rate is achieved. Most importantly, this additive manufactured structure provides a new way for the design and fabrication of wideband MAs.”

3D printing offers low cost, high efficiency, and convenience, but when it comes to making wideband MAs with the technology, it does lack an appropriately stable and tractable high-resistive film, as the typical materials used for this don’t work with 3D printing. But, the team thought that the absorption bandwidth of the MA could be increased by using highly conductive plastic.

Photographs of the fabrication process: (a) 3D printing PLA material layer; (b) fabricated sample

“The proposed structure provides new opportunities for the design and fabrication of wideband MAs,” the researchers wrote.

The team’s proposed wideband MA is made of a patterned conductive plastic layer embedded in a layer of PLA, the bottom of which is covered with a copper ground film.

“First, a PLA layer with grooves is 3D printed,” the researchers wrote. “Next, the patterned conductive plastics were placed in these grooves, and then the PLA is continually printed above the patterned plastics to seal them. Finally, copper is pasted on the bottom surface of the PLA layer.”

Once they verified that the MA would work, they tested its absorption spectrum, which is greater than 90% from 16.3 to 54.3 GHz. The absorber has a thin thickness and high absorptivity, along with polarization insensitivity. The researchers used numerical simulations of the absorber to demonstrate its mechanism, efficiency, and the surface loss for both the copper ground layer and conductive plastic layer, the latter of which “contributes most power absorption of the absorber for both resonant modes.”

The researchers explained, “Hence, the conductive plastic layer plays an important role in the wideband absorption.”

Measurement setup.

The design was verified in a free space experiment, and the researchers used two horn antennas, connected to a network analyzer, measured the sample’s performance charactertistics in the 18−40 GHz frequency range. This showed that their MA design achieved “a good agreement between the simulated and measured results.”

The research team showed that they could save money and simplify things by 3D printing an effective, high-performance wideband MA based on conductive plastic. Their design strategy also made the 3D printed structure insensitive to wave polarization.

“This study is expected to reveal the potential applications of additive manufacturing technology in the realization of wideband electromagnetic wave absorbers,” the researchers concluded.

Co-authors of the paper are Yujiao Lu, Baihong Chi, Dayong Liu, Sheng Gao, Peng Gao, Yao Huang, Jun Yang, Zhiping Yin, and Guangsheng Deng.

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Comparing 3D Printed Parts Made with Virgin and Recycled PLA

While 3D printing continues to grow in leaps and bounds, it still creates a lot of waste, due to removed support structures, disposable prototypes, failed prints, and multiple iterations. Luckily, PLA is biodegradable, and the waste can be easily managed in multiple ways, such as combustion, composting, and dumping it in landfills. However, the best method is recycling: in terms of its environmental impact, it’s 16 times better than combustion and 50 times better than composting, and its carbon footprint is 3,000 times less than that of some plastics based in petroleum, like ABS.

Over the years, many 3D printing companies have started to offer 3D printing filament that’s made from recycled consumer waste, and even recycled filament itself. There are also filament extruders available for people who want to recycle their used material at home. Researchers Isabelle Anderson recently published a paper, titled “Mechanical Properties of Specimens 3D Printed with Virgin and Recycled Polylactic Acid,” about her work evaluating the various properties of 3D printed test specimens made with virgin PLA filament, and comparing them to specimens fabricated with PLA filament made from recycling the original 3D printed specimens.

Testing tensile specimens on the Instron 3369.

The abstract reads, “With the 26% annual growth rate of additive manufacturing, especially in the area of 3D polymer printing, the amount of waste is increasing at a rapid rate. Limited research in the area of recycling has been produced, yet there are several recycling machines being developed for home use. Despite this work there is no published mechanical data on components produced with filament recycled from 3D printed parts. There is very limited data on mechanical properties of any 3D printed materials. This article compares the properties of parts 3D printed with virgin polylactic acid (PLA) to those printed with recycled PLA. Using commercially available PLA and an entry level 3D printer, tensile and shear specimens were produced and then tested for tensile yield strength, modulus of elasticity, shear yield strength, and hardness. The specimens were then ground up and re-extruded into filament, and a second set of specimens were produced and tested using this recycled PLA filament. Mechanical testing showed that 3D printing with recycled PLA is a viable option. With the recycled filament, tensile strength decreased 10.9%, shear strength increased 6.8%, and hardness decreased 2.4%. The tensile modulus of elasticity was statistically unchanged. Although the average mechanical properties before and after recycling were similar, there was more variability in the results of the recycled filament. Additionally, when printing with the recycled filament there was some nozzle clogging, while none occurred with the virgin filament. Overall, the mechanical properties of specimens 3D printed from recycled PLA filament were similar to virgin properties, encouraging further development in the area of recycling 3D printed filament.”

Distributive recycling at businesses and homes, when compared to centralized recycling, can reduce greenhouse gases, and could potentially save more than 100 million MJ of energy each year. However, there isn’t a lot of data about the mechanical properties of virgin 3D printed plastics, and even less about recycled 3D printed plastics.

Anderson chose to evaluate PLA in her study because it’s fairly easy to recycle into filament, and 3D printed all of the specimens on a Flashforge Creator.

“Initial test specimens were produced using virgin PLA filament with a nominal diameter of 1.75 mm. Tensile specimens were fabricated according to American Society of Testing Materials (ASTM) standard D638-14 Type IV,” Anderson wrote in the paper. “The shear specimens were fabricated as square plates with dimensions of 51.2 × 51.2 × 3.9 mm.”

ASTM D638-14 type IV tensile test specimen.

Tensile and shear testing were both conducted on an Instron 3369 Testing Machine, while a handheld Shore D digital durometer was used to test hardness four times from the middle of the shear specimens. After the specimens made with virgin PLA filament were tested, Anderson sent them to Filabot, where they were then ground and re-extruded into 1.75 mm 3D printing filament.

“When the re-extruded filament was received the second set of tensile and shear specimens were produced using the same equipment, software, and method as used on the first set. These specimens were then tested with the same equipment and methods described above,” Anderson wrote.

The results showed that the properties of the specimens 3D printed with virgin PLA were similar to those of the recycled filament, which is “encouraging for the advancement of recycling technology in the area of 3D printing.”

“Although there were some minor difficulties working with the recycled filament, it produced specimens with very usable properties,” Anderson wrote in the paper. “These data are some of the first with large sample sizes, of 25–32, showing tensile, shear, and hardness values for 3D printed PLA, in both a virgin and a recycled format. This verifies that, using an entry level 3D printer, components can be produced with filament recycled from previously 3D printed parts with consistent mechanical properties that are only slightly less than the original parts.”

ASTM shear testing fixture D732-10.

The two types of specimens even looked similar, displaying consistent surface finish and diameter. However, there were some differences between the recycled and virgin PLA, including the fact that the average mechanical properties of the 3D printed recycled specimens were 2-11% lower than those of the prints made with virgin PLA. Additionally, the average shear strength of the recycled material was 6.8% higher than that of the virgin PLA. But there are several possible reasons for these discrepancies, such as a different Poisson’s ratio.

“This project produces valuable baseline data on 3D printed PLA and validates the recycling process with similar data using recycled PLA,” Anderson concluded. “The data produced demonstrates that recycling 3D printed scrap materials into usable filament can yield parts with similar properties to parts produced with virgin filament. This creates the potential to save significant amounts of raw materials, cost, energy, and CO₂ emissions in the production of 3D printed components.”

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UPC Researchers Develop New Method of Designing Porous Scaffolds for FDM 3D Printing

Trabecular structure with thin walls.

From manufacturing customized prosthetics and implants to surgical planning and bioprinting organs and tissues, 3D printing has many medical applications. In terms of bone tissue engineering and 3D bioprinting, 3D printed scaffolds are used as templates to help with tissue formation and initial cell attachment, as well as to fix prostheses through osseointegration. We’ve seen scaffolds made with all sorts of materials, like a compound in turmeric, sugar, and plastic, but the best are those with good porosity that can simulate tissue.

It’s not always easy to fabricate porous structures with specific pore sizes using FDM technology. A trio of researchers from the Polytechnic University of Catalonia (UPC) in Barcelona published a paper, titled “3D Printing of Porous Scaffolds with Controlled Porosity and Pore Size Values,” explaining how they developed a new method of designing porous scaffolds for FDM 3D printing.

The abstract reads, “The present paper provides a methodology to design porous structures to be printed. First, a model is defined with some theoretical parallel planes, which are bounded within a geometrical figure, for example a disk. Each plane has randomly distributed points on it. Then, the points are joined with lines. Finally, the lines are given a certain volume and the structure is obtained. The porosity of the structure depends on three geometrical variables: the distance between parallel layers, the number of columns on each layer and the radius of the columns. In order to obtain mathematical models to relate the variables with three responses, the porosity, the mean of pore diameter and the variance of pore diameter of the structures, design of experiments with three-level factorial analysis was used. Finally, multiobjective optimization was carried out by means of the desirability function method. In order to favour fixation of the structures by osseointegration, porosity range between 0.5 and 0.75, mean of pore size between 0.1 and 0.3 mm, and variance of pore size between 0.000 and 0.010 mm² were selected. Results showed that the optimal solution consists of a structure with a height between layers of 0.72 mm, 3.65 points per mm² and a radius of 0.15 mm. It was observed that, given fixed height and radius values, the three responses decrease with the number of points per surface unit. The increase of the radius of the columns implies the decrease of the porosity and of the mean of pore size. The decrease of the height between layers leads to a sharper decrease of both the porosity and the mean of pore size. In order to compare calculated and experimental values, scaffolds were printed in polylactic acid (PLA) with FDM technology. Porosity and pore size were measured with X-ray tomography. Average value of measured porosity was 0.594, while calculated porosity was 0.537. Average value of measured mean of pore size was 0.372 mm, while calculated value was 0.434 mm. Average value of variance of pore size was 0.048 mm², higher than the calculated one of 0.008 mm². In addition, both round and elongated pores were observed in the printed structures. The current methodology allows designing structures with different requirements for porosity and pore size. In addition, it can be applied to other responses. It will be very useful in medical applications such as the simulation of body tissues or the manufacture of prostheses.”

Cross-section of specimen 1: (a) 3D view, and (b) 2D view.

In order to design 3D printed porous scaffolds that can simulate tissues, they need mechanical strength, which helps with protection and support; permeability, which can direct the transport of nutrients; and surface area and interconnectivity, both of which relate to good cell growth. Other researchers have tried to achieve the necessary porosity in scaffolds by using hierarchical design and topology optimization. But the UPC team went a different way.

“Unlike other methods that are based on truss structures, the present model allows obtaining irregular porous structures from random location of columns in the space, which leave voids among them. Specifically, the structure was modelled with parallel planes joined by columns, with a certain number of columns on each plane,” the researchers wrote.

They applied their model to a disc shape and defined three different variables:

Distance between parallel planes
Number of base points for columns on each plane
Radius of each column

Then, the team used dimensional analysis to lower the number of process variables to just two, and so defined their requirements “for a specific application case: the use of a porous structure in external layers of hemispherical hip prostheses.”

Printed porous structure (rescaling of the designed scaffold by scaling factor of five).

To compare the results of their experiment with computationally calculated results, the researchers used a dual-extruder Sigma 3D printer from BCN3D to fabricate three sample scaffolds out of PLA, then measured their pore size and total porosity. The researchers found that the measured results were not dissimilar to the calculated results.

“In future work, other requirements for structures, related to either mechanical strength or mass transport, will be addressed. In addition, improvement of the FDM printing process is required in order to obtain more accurate and smooth parts,” the researchers concluded.

Co-authors of the paper are Irene Buj-Corral, Ali Bagheri, and Oriol Petit-Rojo.

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Is 0.14mm the Best Layer Thickness for my FDM 3D Prints?

FDM

According to research, the most commonly-used extrusion 3D printing method is fused deposition modeling, or FDM, which is used often for 3D printing larger, stronger parts; it’s also a popular desktop 3D printing method. The technology melts filaments like ABS and PLA into liquid using the heater’s extrusion head; then, the molten materials are then extruded. The semi-fluid material solidifies within 1/10 of second into layers to build a 3D printed part.

A 3D printed object has to be able to support the weight of its own layers, and if you’re looking to make your prints more efficient, you can lower their height. Junhui Wu, with the Jiangxi Water Resource Institute’s Department of Electrical and Mechanical Engineering, wrote and published a paper, titled “Study on optimization of 3D printing parameters,” that discusses how “the influence of the parameters on the printing efficiency is derived from the analysis of the printing parameters” of an FDM 3D printer using PLA material.

The abstract reads, “With the development of 3D printing technology, the application of 3D printing has become more and more widespread, and the 3D printing efficiency problem that ensued has caused more and more researches. This paper will use the melt deposition type (FDM) forming printer. The printing consumables PLA and cylinder model were used as objects to study the effect of slice height on printing time, consumables, and dimensional accuracy and related parameters were optimized. The results showed that when the layer height was 0.14mm, the shortest printing time can be obtained on the premise of ensuring the quality of printing.”

Figure 1-1: 3D printing equipment; Figure 1-2: Testing model

A Raise3D N2 Plus 3D printer was used for this research, set with a nozzle temperature of 210°, a fill rate of 10%, and a starting print layer thickness of 2 mm; the diameter of the model is 10 mm, with a height of 15 mm.

The thickness was increased little by little for tests, and the print time was recorded with a stopwatch. Analysis of the data shows that the print speed was slower when the layer heights were smaller; on the flip side, print speed increases but the model becomes rough when the layer is thicker.

Next, the paper looks at the relationship between 3D printing supplies and layer height.

The paper reads, “According to the printing consumables required to set different floor height tests, the slicing software is used to measure the consumables of the printed products according to different floor heights.”

The results of this experiment show that when the floor height increases, so too do the consumables; however, they “have little effect.”

The last experiment the paper describes is the effect of layer height on the dimensional accuracy of the print size. This accuracy was tested at different layer heights; then, the workpiece’s dimensional error was measured from the X, Y, and Z directions with a digital caliper. The experiment showed that a print’s dimensional accuracy is higher when the layer heights are smaller. Additionally, the rate of dimensional accuracy would increase when the height did.

Figure 3-1: Layer height, printing time, consumables, and accuracy

The figure above illustrates the relationship between layer height and consumables, accuracy, and the total print time. The results of these experiments show that a layer height of 0.14 mm allows users to achieve the shortest FDM 3D printing time “under the premise of ensuring the print quality.”

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