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Ireland: Characterizing Mechanisms of Metallic 3D Printing Powder Recycling

In order to cut down on material waste, and save money, laboratories will often reuse leftover metal AM powder. A trio of researchers from the I-Form Advanced Manufacturing Research Centre in Ireland published a paper, “X-ray Tomography, AFM and Nanoindentation Measurements for Recyclability Analysis of 316L Powders in 3D Printing Process,” focusing on better understanding and characterizing the mechanisms of metallic powder recycling, and evaluating ” the extent of porosity in the powder particles,” in order to optimize how many times recycled powder can actually be reused in the powder bed fusion process.

Many “risk-tolerant applications,” like in the aviation and biomedical industries, will not use recycled powder, because any part abnormalities that can be traced back to the material can be unsafe and expensive. Parts 3D printed out of recycled powder need to have mechanical properties, like hardness and effective modulus, that are comparable to those of fresh powder parts.

“In order to reuse the recycled powders in the secondary manufacturing cycles, a thorough characterization is essential to monitor the surface quality and microstructure variation of the powders affected by the laser heat within the 3D printer. Most powders are at risk of surface oxidation, clustering and porosity formation during the AM process and it’s environment [1,2],” they explained. “Our latest analysis confirms the oxidation and the population of porous particles increase in recycled powders as the major risky changes in stainless steel 316L powder [3,4].”

A common practice before reusing recycled powders is sieving, but this doesn’t lower the porosity or surface oxidation of the particles. Additionally, “the subsequent use of recycled powder” can change the final part’s mechanical strength, and not for the better.

“Here, we report our latest effort to measure the distribution of porosity formed in the recycled powders using the X-ray computing technique and correlate those analyses to the mechanical properties of the powders (hardness and effective modulus) obtained through AFM roughness measurements and nanoindentation technique,” the researchers wrote.

They used stainless steel 316L powder, and printed nine 5 x 5 x 5 mm test cubes on an EOSINT M 280 SLM 3D printer. They removed the recycled powder from the powder bed with a vacuum, and then sieved it before use; after the prints were complete, they collected sample powders again and labeled them as recycled powders.

“Both virgin and recycled powders were analyzed by number of techniques including XCT and Nanoindentation. XCT was performed by X-ray computed tomography (XCT) measurements were performed with a Xradia 500 Versa X-ray microscope with 80 KV, 7 W accelerating voltage and 2 µm threshold for 3D scan,” they wrote.

“To measure the roughness of the virgin and recycled powder particles, we performed Atomic Force Microscopy (AFM) and confocal microscopy using the Bruker Dimension ICON AFM. The average roughness was calculated using the Gwyddion software to remove the noise and applying the Median Filter on the images as a non-linear digital filtering technique.”

The researchers also ran nanoindentation on multiple powder particles, under a force of 250 µN for no more than ten seconds, in order to determine “the impact of porosity on the hardness and effective modulus of the recycled powders,” and used an optical microscope to identify pore areas on the powder.

XCT imaging of powder. (a) 3D rendered image of 900 recorded CT images, (b) region of interest, (c) internal pores in particles indicated in a 2D slice, (d) identified pores inside particles after image processing.

The XCT images were analyzed, and “a region of interest” was chosen, seen above, from which pore size and interior particle distribution were extracted.

AFM image on a particle showing the boundary of mold and steel and the area where surface roughness was measured.

Software was used to process the AFM topography images of both the virgin and recycled powders, and the team applied nanoindentation on different locations of the particles, with a force of 250 µm.

(a) powder particles placed on hardening mold for nanoindentation, and (b) an indent applied on a particle surface.

They determined that the reused powder particles had about 10% more porosity than the virgin powder, and the average roughness of the powder particle surfaces was 4.29 nm for the virgin powder and 5.49 nm for the recycled; this means that 3D printing “may increase the surface roughness of the recycled particles.” Nanoindentation measurements show that the recycled powder has an average hardness of 207 GPa, and an average effective modulus of 9.60 GPa, compared to an average of 236 GPa and 9.87 GPa for the virgin powder, “which can be correlated to porosities created beneath the surface.”

Pore size distribution in virgin and recycled powders extracted from image processing on XCT measurements.

“The pore size in recycled powders has a wider distribution compared to virgin counterpart. The main population of pore size is around 1-5 µm in virgin powder which slightly reduces to bigger size but for a smaller population. There are also bigger pores in recycled powder but with a smaller population,” they noted. “On the other hand, looking at higher pore population in virgin powder (around 10 µm size), we believe that the out-diffusion of metallic elements to the surface occurs during laser irradiation.”

Surface roughness plots from AFM measurements on powder particles. Average roughness calculated by Gwyiddion software.

The recycled powder hardness, which is smaller than in the virgin powder, “could be attributed to higher pore density in recycled particles,” since porosity causes the powder to be “more vulnerable to the applied force resulted in smaller hardness.”

While change in grain size of the powder particles can lead to reduced mechanical properties, the team’s AFM and SEM results did not show much grain redistribution in the recycled powder. But, their nanoindentation and XCT results did find that higher powder porosity can decrease both the hardness and modulus of the particles, which “will damage the mechanical properties of the manufactured parts.”

Hardness and effective modulus of fresh and virgin particles by nanoindentation.

“We have previously presented our achievement on surface and size analysis using SEM and XPS analysis. Here, we focused on pore distribution in both powders and correlated that to surface roughness, hardness and effective modulus obtained from nanoindentation analysis of the powder particles,” the researchers concluded. “The results indicate that pores population is about 10% more in recycled powders affected by the laser heat and oxygen inclusion/trap in the powder, which in turn, increases the surface roughness but reduces the hardness and modulus of the recycled powders. The pores are filled with gases (such as Argon or Oxygen) since these gases are not able to skip the melt and have a lower solubility in the melt throughout the solidification process.”

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Investigating Properties of Virgin, Sieved, and Waste 316L Metallic Powder for SLM 3D Printing

We often see metal 3D printing used to make steel parts, so plenty of research is being done regarding the material properties. Researchers from VSB – Technical University of Ostrava in the Czech Republic published a paper, “Research of 316L Metallic Powder for Use in SLM 3D Printing,” about investigating Renishaw’s AISI 316L powder for use in Selective Laser Melting (SLM) technology.

“Understanding the SLM process is extremely challenging, not only because of the large number of thermal, mechanical and chemical phenomena that take place here, but also in terms of metallurgy. The presence of three states (solid, liquid, gaseous) complicates the ability to analyze and formulate a model formula for proper simulation and prediction of part performance when printed,” they explained. “Since the SLM process operates on a powder basis, this process is more complicated by another factor compared to the use of other bulk material. The properties of the used printing powder define to a large extent the quality of the finished part.”

Because the material can impact an SLM 3D printed part’s final properties, powder research should be done ahead of time for best results. Particle size, shape, flowability, morphology, and size distribution are key factors in making a homogeneous powder layer, and using gas atomization to produce spherical particles helps achieve high packing density; this can also be improved with small particles.

The researchers investigated three phases of metallic powder present in the SLM process – virgin powder (manufacturer-supplied), test powder that had been sieved 30 times, and waste powder “that had settled in the sieve and was no longer being processed and disposed of.” They used a non-magnetic austenitic stainless steel, alloyed with elements like nickel and chromium and containing a low percentage of carbon.

Scanning electron microscopy (SEM) was used to investigate the powder morphology, which “affects the application of metal powder by laser in terms of fluidity and packing density.” First, the shape of the powder particles was measured and evaluated, and then a visual quality evaluation was completed to look at the spherical quality and satellite (shape irregularity) content. The team found that many particles had satellites, but that this number increased in over-sized powder.

Fig. 1. SEM image of virgin powder 316L, magnification x180

“The measurement of virgin powder (Fig. 1) reveals that the production of powder by gas atomization is not perfect and the shape of some particles is not perfectly spherical,” the researchers wrote. “It is also possible to observe satellites (small particles glued to larger ones, Fig. 2), which are again a defect of the production method.”

Fig. 2. Satellite illustration, magnification x900

They found that the particle shape was “not always isometric,” and that cylindrical, elongated, and irregular shapes appeared alongside spherical particles in over-sized powders.

“Another interesting phenomenon was manifested in the sieved powder, where particles with a smoother and more spherical surface were observed than the original particles. This is most likely due to the melting and solidification process that is specific to AM,” they noted.

Fig. 3. Morphological defects – a) particle fusion; b) gas impurities; c) agglomeration – sintered particle;
d) dendritic particle structure; e) spherical particle; f) particles with a satellite

An optical method was used to measure powder porosity. The 316L powder was embedded in a resin, and was “1 mm layer abraded” post-curing before the particles were cut in half and polished with diamond paste. The images captured via microscope were loaded into analysis software, which determined that the total density of the powder was 99.785%.

“In general, pores must be closed from 3/4 of their circumference to be considered pores,” the team explained. “Particles that do not comply with this rule are automatically considered irregular particles.”

Fig. 4. An example of open pores that correspond to the rule (L), and pores that do not conform (R)

The researchers also measured the size of all individual pores and recorded which ones began at 5 µm, though they noted that due to potential image resolution issues, “pore sizes of about 5-8 μm should be taken with some uncertainty.”

Fig. 5. Pore size measurement of 316L metallic powder

A histogram showed that, in the metallic powder particles, the “15 µm pore size was most present,” and that the largest was 30 µm.

Table 3. Measured values of porosity of powder particles

Finally, they used an optical method to measure and examine grain size distribution of the virgin and sifted powder. Using 200x magnification, measurements were taken at five random locations, each of which had roughly 200 particles on which they performed static analysis. The results were processed with statistical software, which created cumulative curves to indicate how many particles were smaller or larger than a certain size.

“Of these, the quantiles d10, d50 and d90 were obtained, which express the cut-off limit within which the size falls to 10, 50, 90 % of the measured particles,” they wrote.

The average particle size only increases a little by repeatedly sieving the metallic powder, but because of irregular particles, agglomerated or molten particles larger than 45 μm, they fall through the mesh. Results show that <10 µm particles are reduced, while larger particles are increased, in the sift powder. But, the team notes that the powder is still usable.

“The sift powder showed an increase in particle volume and surface area while circularity decreased, indicating that virgin powder generally has a higher sphericity,” the team explained.

They found defects like agglomeration, gas impurities, and particulate fusions at all three stages, but since the powder is still usable, they concluded that SLM is both an economic and ecological technology. The researchers listed several measures to take in order to “achieve the best possible consolidation,” such as high purity, fine surface, low internal porosity, tight particle distribution, and as few surface pores and satellites as possible.

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Ti6Al4V in Selective Laser Melting: Analysis of Laser Polishing Techniques

Chinese researchers are expanding on new materials and technology for improving surface quality in metal 3D printing, outlining their findings in ‘Laser Polishing of Ti6Al4V Fabricated by Selective Laser Melting.’ SLM technology allows for fabrication of complex parts and is becoming increasingly more popular due to the latitude allowed for designers and researchers, as well as greater efficiency in production.

In this study, the researchers focus on the positive benefits for bioprinting, and the versatility offered for fabrication of implants related to bone fusion. Inferior surface finish is one of the greatest challenges, however, resulting in the following issues:

Stair-step effect
Low-dimensional precision
Increased friction
Low therapeutic effect

“Various conventional post-processing treatments, such as sandblasting, chemical polishing, electrolytic polishing, machining, ultrasonic polishing, and oxidation have been used on metallic AM (Additive Manufacturing) components to reduce their surface roughness. However, several drawbacks, such as being time-consuming, it is difficult to obtain machine precision components, chemical risks, and low efficiency, limit the clinical application and development of these treatments,” explain the authors.

Laser polishing can solve some of these problems, working with smaller, complex parts that require accuracy, and offers the capability of high-speed polishing at lower cost. Laser polishing also refines mechanical properties, offering improvement which is of ongoing interest to users around the world whether in experimenting with composites, color, 4D materials, or more.

“A comprehensive analysis of the roughness, porosity, fatigue behavior, and biocompatibility, along with the relationships between them, of components after LP should be conducted prior to applying LP technology to implantable medical devices,” explained the researchers regarding the motivation for their study, as they worked to improve on surface roughness and resulting finish.

“The findings of this study can play a guiding role in other processes that involve biomedical materials,” said the researchers.

All samples, created with Ti6Al4V alloy, were polished in a rectangular cavity with argon, used to decrease the possibility of oxidation on parts.

(a) Test specimens; (b) a schematic view of the laser polishing (LP).

During analysis, samples displayed metallic ‘globules,’ which the researchers noted were ‘only loosely bonded during additive manufacturing processes. Small particles and microcracks persisted, however, displayed on the LP-1 sample, while the LP-2 sample was polished with no defects. For sample LP-3 there was concern over reconstructed islands and cracks.

Scanning electron microscope (SEM) images of the (a) as-received sample, the (b) LP-1 sample, the (c) LP-2 sample, and the (d) LP-3 sample.

Laser scanning confocal microscope (LSCM) images of the (a) as-received sample, the (b) LP-1 sample, the (c) LP-2 sample, and (d) the LP-3 sample.

While laser treatments caused changes that affected wettability, the authors note that some previous research has shown a positive connection related to surface topography. In evaluating pore distribution, samples were analyzed as the researchers sliced then from a variety of lengths from the surface. All samples displayed mechanical properties that were similar, in terms of tensile and yield strength and elongation. With the exception of the high-cycle fatigue test, fatigue behavior was almost the same in all samples.

The pore distribution of the as-received sample at different distances: (a) 0–10 μm; (b) 30–40 μm; (c) 60–70 μm, and (d) 70–100 μm. The pore distribution of the LP-2 sample at different distances: (e) 0–10 μm; (f) 30–40 μm; (g) 60–70 μm; and (h) 70–100 μm. (The purple part of the image, after threshold segmentation, is the pore.)

Mechanical properties: (a) microhardness distributions in the laser-polished layer, (b) tensile properties, (c) stress–life fatigue behavior for all geometries showing combined data points, and (d) stress life fatigue curves.

“The cell experiment showed that the LP-2 parameters improved cell adhesion and exhibited cell proliferation. The results indicate that LP improved the cell biocompatibility, while hydrophilicity positively affected early cell adhesion,” concluded the researchers.

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Adhesion and proliferation of MC3T3-E1 cells grown on different sample surfaces. (a) The as-received sample, (b) the LP-1 sample, (c) the LP-2 sample, and the (d) LP-3 sample. In images a–d: F-actin cytoskeleton of osteoblasts (red) and cell nuclei (blue) after 1 day of seeding.

[Source / Images: ‘Laser Polishing of Ti6Al4V Fabricated by Selective Laser Melting’]

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Researchers Compare Microstructure of As-Cast, Hot-Extruded, and 3D Printed Magnesium Alloy Samples

Fig. 1: SEM micrographs of the WE43 alloy powder

Alloys of the shiny gray chemical element magnesium (Mg) feature a high strength-to-weight ratio and a low density of about 1700 kg/m3, making them good options for technical applications in the automotive, aviation, and medical fields. But it’s been determined that their weight can be further decreased if porous structures are formed – which can be achieved with 3D printing. A team of researchers from the University of Chemistry and Technology Prague and the Brno University of Technology, both in the Czech Republic, wanted to study the microstructure of a particular magnesium alloy after it had been fabricated using three different methods: as-cast, hot-extruded, and 3D printed with SLM technology.

SLM 3D printing can achieve complex geometric shapes, but there are issues when it comes to fabricating magnesium alloys with this process, mainly high reactivity of magnesium powder, which can lead to unsafe oxide particles forming within 3D printed parts. Patrícia Krištofová, Jiří Kubásek, Dalibor Vojtěch, David Paloušek, and Jan Suchý recently published a study, titled ” Microstructure of the Mg-4Y-3RE-Zr (WE43) Magnesium Alloy Produced by 3D Printing,” about their work mapping an SLM 3D printed magnesium alloy’s microstructure.

“Magnesium alloys made in the form of 3D printing are relatively new production processes,” the researchers wrote. “The study therefore this process compared with current processes, which are now well known and mapped. It was therefore studied the microstructure produced by three different processes of production. The microstructure and chemical composition of present phases were studied using scanning electron microscopy (SEM) and energy dispersive xray spectrometry (EDS). Based on the microstructural examination, significant differences were found between the materials produced by different production processes. The microstructure of the as-cast alloy consisted of relatively coarse α-Mg dendrites surrounded by eutectics containing intermetallic phases rich-in alloying elements. During hot extrusion, the eutectics fragmented into fine particles which arranged into rows parallel to the extrusion direction. The 3D printed alloy was characterized by significantly refined microstructure due to a high cooling rate during the SLM process. It consisted of very fine dendrites of α-Mg and interdendritic network enriched-in the alloying elements. In addition, there were also oxides covering original powder particles and the material showed also some porosity that is a common feature of 3D printed alloys.”

The team used an SLM Solutions 280HL 3D printer to fabricate 15 × 5 × 60 mm rectangular samples of WE43 magnesium alloy, and used SEM and EDS to study their microstructures; then, these were compared to identical materials that had been manufactured through simple gravity casting and hot extrusion.

“The first sample was an as-cast ingot of 60×80×500 mm in size purchased from an industrial supplier. The second WE43 alloy sample was prepared by hot extrusion of the ingot. Cylinders with a diameter of 30 mm and a length of 60 mm were directly cut from the ingot and then extruded at 400°C, extrusion rate of 2 mm/s and extrusion ratio of 16. The resulting extruded rods had a diameter of 7.5 mm,” the researchers explained.

“The analysis revealed that 10% of the WE43 alloy powder particles had a size of 26.9 μm, 50% to 39.8 μm and 90% to 57.9 μm. Thus, the powder contains a sufficient amount of both larger and smaller particles. With respect to the particle size, the size of the building layer was 50 μm.”

The team conducted microscopic observations of the samples, and you can see the views of their microstructures in Figure 2.

Fig. 2: SEM micrographs of the WE43 alloy: a) as-cast, b) hot extruded, c) 3D printed by SLM, d) 3D printed by SLM – detail.

The as-cast alloy has a coarse microstructure, while the microstructure of the sample fabricated with hot extrusion was “considerably” modified. The microstructure of the 3D printed sample is completely different from the other two, featuring regions about 20-50 µm in size that are surrounded by thin boundaries.

“In addition, residual porosity is observed as dark areas between grey regions. The shape and size of grey regions indicates that these regions correspond to original powder particles, either totally or partly melted by laser beam,” the researchers explained. “A more detailed image in Fig. 2d shows very fine internal microstructure of these particles. It contains α-Mg dendrites (dark) surrounded by interdendritic regions (light) enriched in Y and RE elements. The average thiskness of dendritic branches is only approx. 3 µm, suggesting very high cooling rates during the SLM process. In literature focused on the SLM process, cooling rates of 103-106 K/s are often reported.”

The researchers also studied the distribution of elements in the material’s structure, which showed that both the hot-extruded and as-cast material samples had very low oxygen concentration. But the SLM 3D printed sample showed a different story, illustrated in Figure 5 and Table 4.

Fig. 5 Microstructure of the SLM WE43 alloy (SEM) and elements distribution maps (EDS).

“First, element maps and point analysis demonstrate an increased concentration of oxygen in the material which is located mainly in pores (point 1) and also at bondaries between melted powder particles. In the particle interior the O-concentration is very low (point 2),” the researchers wrote. “Second, element map in Fig. 5 also indicates increased content of Y at powder particle boundaries. It can be assumed, that partial oxidation of the powder occurred during the SLM process inside the building chamber. Most probably, the atmosphere contained traces of residual oxygen which reacted preferentially with yttrium due to a high chemical affinity of these elements. For this reason, imperfect connection between powder particles and porosity are observed.”

Results show that an SLM material’s microstructure is “extremely fine” because of high cooling rates, and will also feature a high oxygen concentration “due to a high affinity of the alloy to this gas.” This creates an “imperfect connection” between powder particles and porosity. The researchers plan further studies of this magnesium alloy in order to produce pore-free compact material and decrease the “harmful influence of residual oxygen.”

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New Aluminum Alloy Development Methodology for SLM Under Development

Authors Qingboa Jia, Paul Rometsch, Sheng Cao, Kai Zhang, Xinhua Wung explain that SLM 3D printing users need some better choices for metals in their recently published, ‘Towards a high strength aluminum alloy development methodology for selective laser melting.’ Because of a limited selection materials, the researchers do not see SLM 3D printing living up to its true potential—especially for use in serious applications such as the automotive industry, aerospace, marine, medical and engineering.

Lightweight aluminum alloys are becoming more popular and are very ‘adaptable’ to SLM 3D printing. These types of alloys are still too limited, however, and the researchers point out that results in 3D printing are often mediocre—leading them to the option of creating a high-performance Al alloy.

Sc (scandium) is a metal element that can be used to strengthen a variety of different alloys—even in just small additions.

“During the SLM process, the solidification rate within molten pools measuring several hundred microns in size can go up to 104–106K/s, which provides the possibility of trapping significantly more Sc into solid solution. After a subsequent ageing treatment, the decomposition of the super saturated Sc in the Al matrix into a correspondingly large volume fraction of nano-sized Al3Sc precipitates provides great potential for precipitation hardening.

The researchers created an easy method to mimic the SLM printing process and predict alloy properties. A wedge mold casting and laser re-melting methodology were used to imitate the SLM solidification process. After that, the researchers were able to create Al-Mn-Sc alloy—both assessed and verified in SLM 3D printing. The ternary Al-Sc-Zr alloy demonstrated a usage hardening response, along with excellent thermal stability. Mn was also chosen as another element to add to the properties of the of the Al-Sc-Zr.

Ageing curves at 300 °C for laser remelted Al-Sc-Zr and Al-7Si alloys. The inset pictures show typical microhardness indentation sizes of samples aged for 168 h. Error bars that arenot showing up are typically within ±0.5 HV0.5

“The SLM-fabricated Al-Mn-Sc alloy demonstrated good laser processability with an absence of solidification cracks and obvious metallurgical defects. Due to the formation of primary Al3(Sc,Zr) particles at the molten pool boundaries, the SLM fabricated Al-Mn-Sc alloy possessed a fine columnar-equiaxed bimodal grain structure.”

“A TEM study confirmed the precipitation of a large volume fraction of nanosized Al3Sc precipitates after a simple and industrially desirable direct post-ageing treatment of 5 h at 300 °C. The direct aged Al-Mn-Sc alloy achieved very high yield strength of 570 MPa together with an elongation to fracture of 18%.”

Direct ageing treatment, and lack of fluctuation during the straining process could be a result of homogeneous distribution of precipitates along dislocation slip planes. The study shows that solutes like Mn, massive precipitation of nano-sizeed Al3Sc, and ‘fine-grained’ structures allowed for ‘outstanding qualities.’

While this work sheds light on new and improved alloys for SLM 3D printing, other materials have been created too such as high entropy alloys, titanium mixtures, and Ti6Al4V Cellular Structures. 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.

(a) Backscatteredelectron (BSE) images showing the cross-sectional microstructures of laserremeltedAl-Sc-Zralloy;(b) highmagnification image showing laser remelted area A in(a); (c) high magnification image showing cast area B in (a); (d) EDS line scan revealing the compos

[Source / Income: ‘Towards a high strength aluminium alloy development methodology for selective laser melting’]

Processing Parameters in SLM 3D Printing: UK Researchers Test Ti6Al4V Cellular Structures

In ‘The influence of processing parameters on strut diameter and internal porosity in Ti6Al4V cellular structure,’ UK researchers from the University of Birmingham look further into strut size and porosity issues during bioprinting, and discuss the overall challenges of selective laser melting (SLM) in additive manufacturing. In this research, SLM 3D printing was used to create Ti6Al4V cellular structures, but with a wide range of different parameters.

While porous structures are attractive in many applications today for industries like automotive and aerospace, when created with titanium alloys they ensure strength, corrosion resistance, and the proper amount of density required. Even more importantly, however, lattice structures like Ti6Al4V offer high biocompatibility. Made up of a network of struts that form cells to make lattices, these complex structures are often manufactured with conventional techniques like casting; however, with AM technology, complex geometries can be produced faster and more affordably.

As the researchers point out however, problems can occur in SLM printing when conditions are not properly optimized—resulting in defects due to a ‘mismatch’ between the 3D design and the 3D print. The team set up an experiment for testing parameters and pinpointing a way to improve SLM methods.

Lattice structure fabricated
using SLM

They created a set of structures ranging from 100W to 300W and scan speed ranging 8000 mm/s to 4000 mm/s. Lattices were assessed regarding the effects of input energy on strut diameters, and porosity levels. As they suspected due to compiled data from previous research studies, increased input energy resulted in increased strut diameters:

“This relation is attributed to the fact that inclined struts were built partially on loose powder, which resulted in adhesion of free powder (partially melted powder particles) to the surfaces of the struts. At high input energy condition, the energy transferred to attach powder particles was high enough to result in full melting of the attached powders and hence became part of the fabricated strut.”

Different zones were created based on changes in input energy:

Zone 1 – low input energy was directed here, leading to ‘discontinuity’ in the strut. The researchers noted this was due to lack of diffusion between melt pools, along with a balling effect that typically causes defects in SLM.
Zone 2 – as the zones ascend in energy, this one is a result of intermediate laser power and scan speed. The researchers noted the formation of irregular defects, again, without diffusion between melt pools. They also noted erratic formation in the struts, resulting in ‘waviness.’
Zone 3 – this zone formed with the pairing of higher laser power but low scanning speed, ‘mitigating the previously formed lack of diffusion defects.’

A diagram showing the variation of Strut diameter as a function of increasing linear input energy diameter.

“SLM processing parameters investigated in the current research shows that the input energy density has a significant influence on the strut diameter and porosity morphology within the fabricated struts. Different zones were developed based on changing the input energy,” concluded the researchers. “Additionally, it was observed that strut diameter size for Ti6Al4V lattice structure increased with increasing the input energy density.”

While much about 3D printing can be deceptively simple, additive manufacturing processes are often more complicated in hardware, software, materials required, and technique. Selective laser melting, although it may offer some challenges, continues to be at the forefront of research projects and studies today, from new procedures created for heat accumulation detection to fabricating steel nuclear components or working with metallic glass. Find out more about strut diameter and porosity issues with this method too 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 images for struts at different fabrication conditions (a) 100W &4000mm/s (b) 200W & 2400mm/s
(c) 300W & 800mm/s

[Source / Images: The influence of processing parameters on strut diameter and internal porosity in Ti6Al4V cellular structure]

Singapore: Researchers Study Effects of Spatter in Large-Scale SLM Printing

Ahmad Anwar, thesis student at Nanyang Technological University in Singapore, explores undesired byproducts of 3D printing in ‘Large scale selective laser melting : study of the effects and removal of spatter by the inert gas flow.’ The topic of spatter is usually considered in regard to imperfections, but here Anwar explores such issues in connection with fabrication on the larger scale too—a necessary method that results in hardware of increasing sizes so that larger parts can be made.

Large scale selective laser sintering can be restricted by powder weight, along with other features such as the number of lasers, and powder bed area. For successful SLM printing, Anwar states that the study of spatter particles is necessary. Spatter is notable due to its size and darker color, and effect on 3D printed layers—along with inducing porosity. The goal of the research study was to find out more about effects of spatter on the manufactured parts, analyze how they impacted mechanical properties, and simulate the activity of spatter in 3D printing during inert gas flow.

Anwar also studied ‘suitable ejection profiles,’ as well as what performance would be like without any inert gas flow at all. The researchers used an SLM Solutions 280 HK machine for their experiments and chose argon as the gas of choice for exploring spatter.”

“With respect to the spatter particles on the powder bed, the mass and size distributions were characterized,” states Anwar. “The Stokes (Suk) number was then used as a parameter to observe the gas flow effectiveness in the spatter transport, which accounts for particles suspended in the gas flow. Image processing was also applied in order to immediately characterize the spatter distribution on the powder bed.”

The researchers set up a camera to monitor spatter and then processed them for comparison with the mass distribution characteristics. As Anwar explains, spatter usually occurs during any SLM printing process as such particles are ejected and often accumulating near processing regions or the powder bed. The volume of spatter is also dependent on energy output like:

Laser power
Scanning speed
Layer thickness
Hatch spacing

Schematic of spatter ejection from melt pool and its transport by the inert gas flow (green arrows) in the -x direction.

Higher energy input resulted in larger spatter, increased scattering, and greater jetting height. As the researchers experimented with methods to reduce the spatter, they pumped gas into the chamber:

“For the SLM Solutions machines, argon gas is pumped in from the right to the left side (in the negative x direction). There are two reasons for the introduction of the inert gas; Firstly, oxidation of the molten powder needs to be minimized as much as possible. Hence, scanning only starts when oxygen content is below 0.05%. Secondly, during the scanning itself, the flow of gas aids in the removal of unwanted spatter as a result of the ionized metal vapor and plasma plume that exert recoil pressure on the melt pool,” stated Anwar.

The researchers collected 15 samples of spatter, with each one measured and evaluated after being scooped from a deposit area near the outlet.

“The reasons why we chose to collect the spatter at that area are: (i) it is not possible to collect the spatter directly on the powder bed as it is mixed with fresh powder; (ii) it is not possible either to collect the powder blown out of the outlet, as one cannot completely clean the powder collector (gas filter) between runs; (iii) on the contrary, the region near the outlet where the powder is collected in our experience could be cleaned up several times per run, resulting in reliable results; (iv) finally, it can be safely assumed that the quantity of the powder collected near the outlet is proportional to the total quantity blown out of the powder bed and that its composition is similar,” states the author.

SEM images of A: Fresh powder; B: spatter collected near the outlet observed;
C: Single particle of spatter. D: Sample EDS result of single spatter

Simulations were performed to analyze how gas crossflow contributes to moving spatter away from laser-scanned regions. Argon gas was not substantially impressive in removing spatter to the outlet. The researchers also found that increasing gas flow velocity did not reduce the number of particles in the powder bed.

“Interest in large scale AM processes have generated much research on the issues hindering the development of larger machines, and it is no exception for SLM,” concluded the author. “The prospects of manufacturing larger parts for the aerospace and automotive industries are deemed to be very attractive.

“The results reported from the experimental and simulation studies of the spatter particle distribution on the powder bed could prove to be significantly and scientifically beneficial for the development of an optimized inert gas flow system. In the future, such improvements made to remove spatter particles over a larger powder bed area would realize the possibility of producing larger SLM machines capable of fabricating even larger parts than current standards.”

Almost as soon as we realized the miraculous potential of 3D printing and the infinite choices for innovation before us, it was time to start critiquing and improving—and just as the technology is based on a layer by layer approach, its continued progress has been made with one improvement mounting on another. Flaws in 3D printing must be addressed, however, as many parts are relied on for strength and functionality. The study of spatter is important in trying to reduce or eliminate any defects. In other studies, researchers have studied ejecta and its role in causing imperfections, other types of spatter, and have even set up high-speed cameras to study 3D printing in situ. Find out more about the impact of spatter in large scale selective laser melting here.

[Source / Images: ‘Large scale selective laser melting : study of the effects and removal of spatter by the inert gas flow’]

Powder accumulation on left side of SLM Solutions 500 HL build chamber

3D Printing News Briefs: April 12, 2019

We’ve got news about a contest to start off today’s 3D Printing News Briefs, followed by some business news and 3D printed jewelry. Weerg has announced the second edition of its “3D Printing Project Award” contest. Moving on, Bastian Solutions worked with Fast Radius to create a robotic materials handler using HP 3D printing, while Fast Radius announced that it has closed a round of Series B funding. Finally, an SLM 3D printer is being used by a person you might recognize to fabricate unique metal rings.

2nd Edition of Weerg’s 3D Printing Project Award Contest

3D printing and CNC machining platform Weerg, based in Gardigiano, Italy, just announced the second edition of its “3D Printing Project Award” contest, which promotes creativity, experimentation culture, and innovation in design manufacturing. The company, which offers the largest Italian installation of HP’s MJF 4210 3D printers, invites designers and developers to create “an iconic object completely printed in 3D” for the chance to win a €500 Weerg coupon, and an interesting social media opportunity – star as the protagonist in a professional video that will highlight his/her designer skills, which Weerg will promote.

“After the success we obtained last edition, we decided to put to test once more our recently doubled and enhanced production department, and to give visibility to the most creative talent in 3D Printing. The Weerg Award was created to stimulate the potential and the desire to innovate of tomorrow’s designers who are starting to come face to face with the opportunities offered by additive manufacturing,” said Weerg’s founder Matteo Rigamonti. “In addition, it will allow us to maximize the performance of HP printers by creating very original and sophisticated items.”

You have until this Sunday, April 14th to submit your entry by posting it directly to Weerg’s Facebook and Instagram pages. The winner will be announced on Monday.

New Robot Warehouse Picker Features 3D Printed Parts

Indianapolis-based Bastian Solutions, a Toyota Advanced Logistics company, has launched its Shuttle System: an efficient, flexible robotic materials handler with dexterity to spare. 45% of the final build-of-material (BOM) on the system’s robotic arm were 3D printed with HP and Carbon 3D printers. The durable polymer joints of the robotic picker were made with HP’s Multi Jet Fusion (MJF) technology, while its fingers and gripper were 3D printed out of unique materials, like EPU 40, using Carbon’s Digital Light Synthesis (DLS) technology. The company displayed its new Shuttle System this week at ProMat 2019 in Chicago.

“We envisioned that additively manufacturing specific parts would make the Bastian Solutions Shuttle System the most efficient and agile robotic picker available on the market. The additive manufacturing process will enable us to customize each robot picker to fit a customer’s particular warehouse environment,” said Ron Daggett, the Vice President of Technology and R&D, Bastian Solutions.

These parts were 3D printed at the Chicago headquarters of industrial-grade additive manufacturing facility Fast Radius.

Fast Radius Raised $48 Million in Series B Funding

Speaking of Fast Radius, the company recently announced that it had raised $48 million in a Series B funding round, which it will use to continue expanding its production-grade AM platform through application engineering, sales teams, and software development. Its software platform, the Fast Radius Operating System (FROS), supports customers across the entire lifecycle of a product, helping them conduct engineering and economic evaluations, find potential applications, and 3D print industrial-grade parts at scale. The funding round was led by the company’s previous collaborator UPS, and Drive Capital was also a strong participant; other participants include previous investors Jump Capital, Skydeck, and Hyde Park Venture Partners.

Pat McCusker, the COO at Fast Radius, said, “This additional funding will allow us to further expand our partnerships with leading global companies across aerospace, consumer, industrial, medical, and automotive verticals.”

Bam Margera 3D Printing Jewelry with SLM Technology

And now for something totally different…Bam Margera, a professional skateboarder, stunt performer, filmmaker, musician, and TV personality who rose to fame as one of the main members of MTV’s reality show Jackass from the early aughts, is now designing jewelry, which he 3D prints on an SLM Solutions 125 system that he purchased. He is selling the unique metal rings and pendants on his official BamMerch website.

According to the website, “BamMerch is Bam Margera´s new lifestyle brand offering various jewelry and apparel, our store launched in December 2016.

“All items are crafted in Estonia, using combination of high-tech metal 3D printing and hand crafting to create extremely unique and detailed jewelry.”

All of the jewelry is 3D printed in-house out of sterling silver, and then carefully polished in ten stages. Some of the pieces, like the pretty Margeras Pendant with three intertwined hearts, are available for as little as $17, with prices ranging all the way up to $149 for the Skull Ring v2. Margera also offers a range of bundles. Check out the video below to see the 3D printing process for some of Margera’s rings, but be warned – if you go searching for more information about his 3D printed jewelry on Twitter or Instagram, there’s a lot of profanity and other NSFW content.

Discuss these stories, and other 3D printing topics, at 3DPrintBoard.com or share your thoughts in the Facebook comments below.

3D Printing News Briefs: December 19, 2018

In today’s 3D Printing News Briefs, a maker has published a free 3D print management app in the Play Store, while Formlabs works to continue accelerating its growth in the Asia Pacific region. America Makes has announced the winners of two Directed Project Opportunities, and a chemist employed by Sinterit has won a prestigious award. Finally, an engineer with a thirst for vengeance used 3D printing and a lot of glitter to get back at the people who steal packages from his porch.

Free 3D Printing App for Filament Management

A new app, simply called 3D Print, is now available to download for free on the Google Play Store. The app was published by a maker who goes by paratiDev on Google Play, and was developed to help other makers better manage their filament.

“It has happened to all of us, you want to print a piece and not to know for sure if you have enough filament in the coil to print it. If you have only one coil of that filament, you have only two options; you can use another filament that has more quantity or risk and print it,” paratiDev writes.

“In the first case it forces you to use another filament different from the one you wanted while in the second case you run the risk that there is not enough filament and the piece remains halfway, assuming a loss of money, filament and time.”

The app allows users to visualize how much filament they have left, view the history of 3D printed pieces they’ve made, and can also generate invoices and quotations for 3D prints. The free 3D Print app also allows you to create projects that group together several pieces, and will visualize the wight and total cost of the project.

Formlabs Continues to Grow in APAC Region

Today, Formlabs announced that its growth in the APAC region is continuing to speed up. The company, which first entered the China market in 2015, is planning to open its new APAC headquarters in Singapore soon, and has also completed a new warehouse in Shenzhen, China for more efficient processing and shipping. While its physical presence in the region is growing, so too is its headcount: Formlabs also announced that David Tan, previously the APAC director of strategy and programs for Oracle Cloud Platform, Alliances & Channels, has been hired on as a new general manager for its own APAC team.

“Formlabs has long set its sights on making 3D printing processes more accessible. Part of this strategy has been completely rethinking 3D printing technologies from the ground up. The second is bringing the technology to market,” explained Max Lobovsky, Co-Founder and CEO of Formlabs. “There is an immense amount of opportunity in Asia Pacific, we’re looking forward to what David and these new locations can do to improve our growing success in the region.”

America Makes Announces Directed Project Opportunities Winners

America Makes has announced the award winners of two Directed Project Opportunities, both of which were funded by the Air Force Research Laboratory (AFRL), Materials and Manufacturing Directorate, Manufacturing and Industrial Base Technology Division. The first is the acceleration of large scale additive manufacturing (ALSAM) project, with the objective of getting past the shortcomings of SLM 3D printing, and America Makes awarded $2.1 million to GE Global Research, in conjunction with GE Additive and the Applied Research Laboratory (ARL) at Penn State. With at least $525,000 in matching funds from the team, the total funding for the ALSAM Directed Project to develop an open source, multi-laser manufacturing research platform will be about $2.6 million.

The second is the advancing AM post-processing techniques (AAPT) project, with a goal of improving process control and lowering costs for qualifying complex parts made with SLM technology. The first awardee is Arizona State University, in conjunction with Quintus Technologies, Phoenix Heat Treating, Inc., and Phoenix Analysis & Design Technologies, Inc., and the second is led by the ASTM International AM Center of Excellence collaborative, in conjunction with Quintus Technologies, Carpenter Technologies Corporation, Aerojet Rocketdyne, Rolls Royce Corporation, Honeywell Aerospace, GE Aviation, and Raytheon. America Makes awarded a total of $1.6 million to the two teams, which will also contribute at least $800,000 in matching funds. Both projects are expected to begin next month.

Sinterit Chemist Makes Forbes List of ’25 Under 25′ Poland

Desktop SLS 3D printer manufacturer Sinterit is proud to announce that its chemist, Paweł Piszko, has been selected by Forbes and the Warsaw office of McKinsey & Company as one of the prestigious “25 Under 25” in Poland. There are five categories in the awards, with five winners in each, and the jury appreciated Piszko’s work on increasing the efficiency of energy collection from renewable sources. When asked by his employers what his goal was, he answered that he wanted to have “an impact on the architecture of society.”

“We are delighted that Paweł chose Sinterit as a place where he can develop his skills and check the results of his scientific activities in practice,” Sinterit wrote in a blog post. “As part of his work, he researches the chemical processes that occur during the sintering of polymers, which allows us to improve the materials that Lisa and Lisa Pro, our flagship SLS 3D printers, print from.”

3DPrint.com congratulates Paweł on this exciting achievement!

Engineer Uses 3D Printed Component to Make Glitter Bomb

Revenge is a dish best served with glitter and fart spray…at least according to a mechanical engineer and evil genius Mark Rober. He spent nine years working at NASA’s JPL – mostly on the Curiosity Rover – and later founded a company called Digital Dudz. He was upset when someone stole a delivered package right off of his porch, and decided to employ all kinds of technology to take revenge.

“I just felt like something needs to be done to take a stand against dishonest punks like this,” Rober said in his YouTube video.

“I spent nine years designing hardware that’s currently roving around on another freaking planet. If anyone was going to make a revenge bait package and over-engineer the crap out of it, it was going to be me.”

Over the course of several months, Rober sketched his idea out, then finished it in CAD before getting to work on the physical prototypes. The package contains a 3D printed component that’s contoured in such a way that four hidden phones inside can capture package thieves opening the box and getting hit with a giant cloud of colorful glitter and continuous blasts of fart spray. Check out his video below to see how things turned out, though be warned that there is some bleeped out profanity. To learn more about the details of his build, check out his friend Sean’s video as well.

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Results of Daimler and BMW AutoAdd Project Show that 3D Printing for Mass Production in Automotive Industry is Possible

[Image: Fraunhofer ILT]

Within the framework of the “Photonic Process Chains” funding initiative by the German Federal Ministry of Education and Research (BMBF), several partners – two research institutes and five companies, to be exact – are focusing on 3D printing in the automotive industry. The “Integration of Additive Manufacturing Processes in Automobile Series Production – AutoAdd” research project is coordinated by Daimler AG, and its findings show that by holistically integrating the metallic laser powder bed fusion process (LPBF), also known as SLM and DMLS, developed at the Fraunhofer Institute for Laser Technology (ILT) into automotive series production, unit costs can go way down.

The BMBF has been working on several projects in order to promote the intelligent linking of photon-based manufacturing processes, like metal 3D printing, as a means to produce complex or individualized products. Its aim is to create flexible, conceptual hybrid manufacturing designs, which can then be used for production purposes. But, out of all 14 joint projects in the funding initiative, which began in 2015 and ended in May, AutoAdd should make it easier to use 3D printing in the automotive industry within just three years.

In addition to Fraunhofer ILT and Daimler, the AutoAdd project partners include:

BMW
GKN Sinter Metals Engineering GmbH
Karlsruhe Institute of Technology (KIT)
Netfabb GmbH
TRUMPF Laser- und Systemtechnik GmbH

[Image: TRUMPF]

These partners are working to lower unit costs by integrating the LPBF process chain into the automotive mass production environment, in order to develop a new hybrid process chain. Daimler and the BMW Group worked together to define the necessary requirements for the new additive process chain, and then Fraunhofer ILT and TRUMPF used the chain to create a variety of plant and finishing conceptual designs for 3D printing.

In addition to a modular system architecture that allows for the use of an “interchangeable cylinder principle” and multiple beam sources, potentially production-ready optical designs were created. The AutoAdd partners also analyzed GKN’s novel scalable materials, as well as created some promising post-processing concepts that could be automated, such as support structure removal.

KIT was the partner which ended up evaluating these new factory designs.

According to a Fraunhofer ILT press release, “Using a simulation model, the engineers of the wbk Institute for Production Science visualized an exemplary, conventional process chain, in which they were able to design various possible LPBF plant concepts. With methods such as cost or benchmark analyzes, they were able to compare the new approaches from a technical and economic point of view with previous ones.”

Long-term recording of the contour exposure during 3D printing of a grinding wheel. [Image: MTU Aero Engines AG]

There were several positive effects stemming from the €3.37 million project, at least in terms of academics. There was enough useful content from AutoAdd to fuel four separate dissertations, and this knowledge can also be used for lectures in the future. Next year, a new project, partially based on the AutoAdd results, will launch that’s focused on line-integration of 3D printing to “implement the designed additive process chain.”

The joint project results are interesting and impressive, showing that it is indeed possible to achieve additive mass manufacturing. For instance, the whole process chain can be automated, making it more efficient and cost-effective, as the team discovered that modular cylinders and wet-chemical immersion baths are effective ways to remove, batchwise, components during post-processing. In addition, common metrics for evaluating LPBF manufacturing equipment were developed by the AutoAdd project partners, which can be used to identify popular equipment manufacturers for a large-scale benchmarking exercise.

“By using standardized benchmark jobs with different test specimens, industrial users can now calculate transferable key figures with which they will be able to find the most economical system for their purposes,” the press release noted.

One of the most, if not the most, important points the AutoAdd team needed in order to make 3D printing ready for series production was the ability to reproduce mechanical properties. The partners took an important fundamental step by demonstrating and evaluating this feature in multiple facilities – showing that it is possible to integrate an economic additive process chain in automotive mass production.

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