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3D Printing News Briefs: November 20, 2019

We’re starting out with some formnext news in today’s 3D Printing News Briefs, as the show is currently taking place in Frankfurt this week. SCANLAB is introducing a new scan system control extension at the show. We also have some metal stories today – Desktop Metal has launched 4140 chromoly steel for its Studio System, while QuesTek Innovations and the German Aerospace Center are exploring the potential of a high-temperature aluminum alloy. Moving on, XJet’s Carmel 1400 AM system was installed at KU Leuven University. Finally, Additive Minds investigated EOS 3D printing without the use of supports.

SCANLAB Integrating Process Data into 3D Printing

Laser scanning solutions manufacturer SCANLAB GmbH is at formnext 2019 this week, and will be introducing a scan system control extension that uses a smart data-acquisition interface that reads external sensors. It’s a functioning model of an intelligent interface, and can integrate sensor data into scan system control – giving AM users the ability to inquire about, and evaluate, centralized process data.

Two tradeshow demonstrators were created that show how diverse the integrable sensor range is. The first incorporates a surface-temperature pyrometer into the scan head control, and the sensor system’s data merges with laser beam position data. In the second, an OCT (optical coherence tomography) sensor from Precitec is integrated to measure the powder bed’s surface topography. Visit SCANLAB at formnext this week at Booth B41, Hall 12.0.

Desktop Metal Launches 4140 Chromoly Steel for Studio System

Massachusetts-based company Desktop Metal is expanding its material portfolio by launching 4140 chromoly steel for industrial applications for its office-friendly Studio System. 4140 is a versatile material, with high tensile strength, abrasion and impact resistance, and toughness. DM Studio Systems users can now use this material to 3D print parts like connecting rods, couplings, pinions, press brake tools, and more for industries including automotive, agriculture, industry, and defense.

“As global demand for the Studio System grows, Desktop Metal is broadening its materials portfolio to include 4140 chromoly steel, enabling designers and engineers to print a broad variety of critical industrial applications, such as couplings, forks, pinions, pump shafts, sprockets, torsion bars, worm gears, connecting rods, and fasteners. Now, teams around the world will be able to leverage the Studio System to iterate quickly on 4140 prototypes and ultimately produce end-use, customer-ready parts faster and more cost-effectively,” said Desktop Metal’s CEO and Co-Founder Ric Fulop.

QuesTek’s 3D Printable Aluminum Alloy

Integrated Computational Materials Engineering (ICME) technologies leader QuesTek Innovations LLC and the German Aerospace Center (DLR) are working on a joint project to explore the potential of QuesTek’s new 3D printable high-temperature aluminum (Al) alloy. The material, able to perform at temperatures between 200-300°C in its as-built condition, is being developed by QuesTek under several US Navy-funded Small Business Innovation Research awards, and is believed to be the first powdered Al alloy to meet necessary requirements without any subsequent heat treatment. The DLR will be 3D printing demonstration components with the material, which can be used to fabricate more lightweight precision components like heat exchangers.

“The accelerated design and development of a printable aluminum alloy capable of meeting so many current needs is especially exciting, as it will enable concurrent design of material composition and component geometry,” stated Greg Olson, QuesTek Chief Science officer. “Based on our internal test results, we see broad application of this material in manufacturing components for aerospace, satellite, automotive and high-performance racing.

“We are particularly pleased to be collaborating with the DLR. Their unrivaled reputation, expertise and close relationship with industry needs will bring an important new scope to our efforts.”

XJet’s Carmel 1400 3D Printer Installed at KU Leuven University

Professor Shoufeng Yang, KU Leuven, shakes hands with Avi Cohen, VP of Healthcare and Education at XJet.

For the first time, a 3D printing system has been installed at a European academic institution. XJet recently delivered its Carmel 1400 AM system to the KU Leuven University in Belgium, where it will be used to for university research and to help develop regional 3D printing medical opportunities. The 3D printer, and its proprietary NanoParticle Jetting (NPJ) technology, will be put to good use at the European research center, as academics will used it to explore medical applications and AM educational and research purposes. XJet’s zirconia material will also be used to 3D print ceramic medical models.

“Since the Carmel was installed, we are already reaping the benefits. The XJet system offers the high levels of precision and exceptional detailing required, levels which were previously impossible or extremely time-consuming in post-processing. The use of soluble support materials, with no harmful powders, makes it a much easier process and opens up opportunities to innovate that simply did not exist before,” said Professor Shoufeng Yang, who is heading the AM research at KU Leuven. “It’s an amazing and fantastic technology for R&D in universities and for the manufacturing industry, and it’s very exciting to be a part of. I believe that this is the best ceramic additive manufacturing method which can be easily upgraded into future multi-materials additive manufacturing, which is a grand challenge in the AM industry.”

XJet is also attending formnext this week – you can find the company at stand #C01 in Hall 12.1.

3D Printing Without Supports

Image credit: EOS

Michael Wohlfart, DMLS Process Consultant for the EOS Additive Minds Process Consulting team, wrote an article on LinkedIn, titled “Building without support? Possibilities and limitations,” about the design aspect of printing without supports in metal powder bed fusion technology, which can reduce build time, material consumption, and cost. The three main reasons for supports are heat transfer, residual stress, and recoater forces, but there are workarounds for all three. In recoater forces, forces are acting on the part while spreading powder, and the recoater will wipe away parts not connected to the baseplate. Prop supports, such as cones and stacking parts, can be used to negate the need for a baseplate connection. Wolfhart discussed a few examples that were 3D printed on an EOS M290 out of titanium.

“Let’s move on to a more advanced design and even incorporate stacking,” Wohlfart wrote. “Since Christmas season is coming up, how about a Christmas tree designed with Siemens NX and pimped with nTopology? By turning it upside-down, the tree is self-supporting and the tree trunk can act as a shell for the next tree. You can see a small overlap of 0.1 mm in x-y-direction between the lattice and the solid parts in order to assure a good connection.”

To learn more, check out Wohlfart’s LinkedIn post.

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The post 3D Printing News Briefs: November 20, 2019 appeared first on 3DPrint.com | The Voice of 3D Printing / Additive Manufacturing.

French Researchers Develop Algorithm to Generate Interior Ribbed Support Vaults for 3D Printed Hollow Objects

Hollowed Bunny printed with our method, using only 2.2% of material inside (compared to a filled model). The supports use 316 mm of filament over a total of 1,622 mm for the print).

In 3D printing, every layer of material must be supported by the layer below it in order to form a solid object; when it comes to FFF 3D printing, material can only be deposited at points that are already receiving support from below. French researchers Thibault Tricard, Frédéric Claux, and Sylvain Lefebvre, from the Université de Limoges (UNILIM) and the Université de Lorraine, wanted to look at 3D printing hollow objects, and proposed a new method for hollowing in their paper “Ribbed support vaults for 3D printing of hollowed objects.”

The abstract reads, “To reduce print time and material usage, especially in the context of prototyping, it is often desirable to fabricate hollow objects. This exacerbates the requirement of support between consecutive layers: standard hollowing produces surfaces in overhang that cannot be directly fabricated anymore. Therefore, these surfaces require internal support structures. These are similar to external supports for overhangs, with the key difference that internal supports remain invisible within the object after fabrication. A fundamental challenge is to generate structures that provide a dense support while using little material. In this paper, we propose a novel type of support inspired by rib structures. Our approach guarantees that any point in a layer is supported by a point below, within a given threshold distance. Despite providing strong guarantees for printability, our supports remain lightweight and reliable to print. We propose a greedy support generation algorithm that creates compact hierarchies of rib-like walls. The walls are progressively eroded away and straightened, eventually merging with the interior object walls.”

Figure 2: A Stanford bunny model is hollowed using a standard offsetting approach. The resulting cavity (R) will not print properly due to local minima (red) and overhanging areas (orange).

While most people think of 3D printing supports as external ones that support overhanging parts of an object, the interior of an object may also need support structures.

“Hollowing a part is not trivial with technologies such as FFF,” the researchers explained. “In particular, the inner cavity resulting from a standard hollowing operator will not be printable: it will contain regions in overhang (with a low slope, see Figure 2) as well as local minima: pointed features facing downwards. There is therefore a need for support structures that can operate inside a part.”

Inner supports should occupy a small amount of space with the print cavity, and the impact on overall print time should be slight. Other researchers have contributed a variety of ideas in terms of support structures with 3D printed hollowed objects, including:

sparse infills
self-supported cavities
external supports as internal structures

“We propose an algorithm to generate internal support structures that guarantee that deposited material is supported everywhere from below, are reliable to print, and require little extra material,” the researchers wrote. “This is achieved by generating hierarchical rib-like wall structures, that quickly erode away into the internal walls of the object.

“Our algorithm produces structures offering a very high support density, while using little extra material. In addition, our supports print reliably as they are composed of continuous, wall-like structures that suffer less from stability issues.”

Hollow kitten model printed with our method and split
in half vertically.

The researchers explained how to support a 3D object by “sweeping through its slices from top to bottom” and searching for any unsupported parts, then adding necessary material below them in the next slice; this material doesn’t need to cover the entire unsupported area, and can take any shape.

“The amount of material added can also be larger than the area needing support. Depositing more material than necessary comes at the price of longer printing times, but can be interesting to significantly improve printability,” the researchers explained. “Large, simple support structures often are faster to print than complex, smaller structures. Indeed, when multiple disconnected locations need to be supported, it is in many cases more effective to print a single, large structure. It encompasses and conservatively supports many small locations. This is more effective than supporting isolated spots, which individual support size may be very small and therefore difficult to print, and which will inevitably increase the amount of travel and therefore print time (taking nozzle acceleration and deceleration into account).”

The team then explained their algorithm for ribbed support vault structures. The idea is to use three main operations to produce supports: propagating and reducing supports from the above slice, detecting areas that appear to be unsupported in the current slice, and adding the supports needed for it.

“Our inspiration comes from architecture, where supports are generally designed in an arch (and vault) like manner. In particular, vaults tend to join walls in any interior space, with only a few straight pillars directed towards the floor. Similarly, many vault structures present hierarchical aspects. Such hierarchies afford for dense supports while quickly reducing to only a few elements – much like trees,” they wrote.

“Within each slice we favor supports having a rectilinear aspect: they provide support all around them while eroding quickly from their ends. Thus, within a given slice, we seek to produce rectilinear features covering the areas to be supported.

“We propose to rely on 2D trees joining the object inner boundaries. Through the propagation-reduction operator, the trees are quickly eroded away (from their branches). Taken together across slices, the trees produce self-supported walls that soon join and merge with the object inner contours, much like the ribs of ribbed vaults.”

The team 3D printed a variety of PLA models with the same perimeters on different systems. Orange models were fabricated on an Ultimaker 3, while the yellow Moai was printed on an Ultimaker 2 and the octopus on a CR-10. A Prima P120 was used to make white models, the blue Buddha was printed on an eMotion Tech MicroDelta Rework, and a dual-color fawn was made on a Flashforge Creator Pro.

Demon dog printed using our method for external support.

The quality of these prints matches models with a dense infill, thanks to the full support property offered, and the algorithm generates multiple small segments that require individual printing, which led to many “retract/prime operations surrounding travels.”

“Depending on the printer model used, the quality of the extrusion mechanics, the user-adjustable pressure of the dented extrusion wheel on the filament, as well as the brand of the filament itself, a small amount of under-extrusion may happen,” the team explained.

“To compensate for this, we perform a 5% prime surplus at the beginning of each support segment: if the filament was retracted by 3 mm before travel, we push it back by 3.15 mm after travel. Because the extra prime may create a bulge, we avoid doing it when located too close to perimeters, so as to not impact surface quality.”

The team also evaluated how much material their method needed, and compared this with materials used for iterative carving and support-free hollowing methods. They also noted how layer thickness impacted support size, and recorded processing times.

Comparison with Support-Free Hollowing and Iterative Carving. The input volume represents the volume (in mm3) and height (in mm) of the model.

“While producing supports of small length, our algorithm is clearly not optimal. This is revealed for instance on low-angle overhangs,” the team wrote. “The inefficiency is due to the local choice of connecting support walls to the closest internal surface, ignoring the material quantity that will have to appear in slices below. While a more global scheme could be devised, it could quickly become prohibitively expensive to compute.”

The researchers concluded that their algorithm ensures complete support of deposited material, which can be helpful for extruding viscous or heavy materials like concrete and clay. They believe that their method for 3D printing hollowed objects through generating ribbed internal support structures could one day lead to novel external support structures as well.

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Researchers Decrease Support Structures for Models Through Multidirectional 3D Printing

An illustration for the idea of the algorithm: (a) a progressively determined planar clipping results for generating the optimized base planes, and (b) the inverse order of clipping planes results in a sequence of regions to be fabricated where the printing direction of each region is the normal of its base plane. The orientation of a printing head is fixed during the procedure of physical fabrication. The parts under fabrication are reoriented to realize the multidirectional 3D printing.

In most planar-layer based 3D printing systems, material collapse is prevented on large overhangs by adding support structures to the bottom. But support structures in single-material 3D printing methods have some major issues, like material waste and the possibility of surface damage. This can be helped by introducing rotation and turning the hardware into a multidirectional system, where models are subdivided into separate regions and each one is 3D printed along a different direction.

L-R: Snowman models fabricated by an FDM 3D printer and the team’s multidirectional 3D printing system by adding only one rotational axis on the same 3D printer.

A team of researchers from Tsinghua University, TU Delft, and the Chinese University of Hong Kong developed two types of multidirectional 3D printing hardware systems: one modified from an off-the-shelf FDM 3D printer with an added rotational degree-of-freedom (DOF), and the other implemented on an industrial robotic arm to simulate a tilting table for two rotational DOFs. They outlined their work in a paper titled “General Support-Effective Decomposition for Multi-Directional 3D Printing.”

The abstract reads, “We present a method to fabricate general models by multi-directional 3D printing systems, in which different regions of a model are printed along different directions. The core of our method is a support-effective volume decomposition algorithm that targets on minimizing the usage of support-structures for the regions with large overhang. Optimal volume decomposition represented by a sequence of clipping planes is determined by a beam-guided searching algorithm according to manufacturing constraints. Different from existing approaches that need manually assemble 3D printed components into a final model, regions decomposed by our algorithm can be automatically fabricated in a collision-free way on a multi-directional 3D printing system. Our approach is general and can be applied to models with loops and handles. For those models that cannot completely eliminate support for large overhang, an algorithm is developed to generate special supporting structures for multi-directional 3D printing. We developed two different hardware systems to physically verify the effectiveness of our method: a Cartesian-motion based system and an angular-motion based system. A variety of 3D models have been successfully fabricated on these systems.”

The researchers wanted to create a 3D printing system that would be able to “add rotational motion into the material accumulation process” to ensure fewer supports, if any. To do so, they created a general volume decomposition algorithm, which “can be generally applied to models with different shape and topology.”

“Moreover, a support generation algorithm has been developed for multidirectional 3D printing,” the researchers explained. “The techniques developed here can speedup the manufacturing of 3D printed freeform models by saving the time of producing and removing supports.”

Progressive results of fabricating models on 4DOF multidirectional 3D printing system and a 5DOF system realized on a robotic arm.

The research team’s paper made several technical contributions, including their support-effective algorithm, which is based on beam-guided search and can be applied to 3D models with handles and loops. In addition, they also summarized decomposition criteria through their multidirectional 3D printing process and created “a region-projection based method” for generating supports for multidirectional 3D printing.

There are, however, some drawbacks involved when changing from one 3D printing direction to another, such as slowing down the process, which is why the researchers “prefer a solution with less number of components, which can be achieve by considering the following criterion of clipping.”

A comparison of decomposition results obtained from three schemes introduced in this paper.

“After relaxing the hard-constraint of support-free into minimizing the area of risky faces as described in JG, the scheme of generating support is considerately vital while both feasibility and reliability should be guaranteed,” the researchers wrote. “To tackle this problem, we propose a new pattern called projected supports that ensures the fabrication of remained overhanging regions through a collision-free multi-directional 3D printing.”

The decomposed and 3D printed results fabricated by the system with 4DOF and 5DOF in motion.

The team applied their algorithm to several models, and were able to reduce, and even eliminate in some cases, the need for support structures. In addition, their method’s “computational efficiency” was on par with general 3D printing time.

“We present a volume decomposition framework for the support-effective fabrication of general models by multidirectional 3D printing,” the researchers concluded. “A beam-guided search is conducted in our approach to avoid local optimum when computing decomposition. Different from prior work relying on a skeletal tree structure, our approach is general and can handle models with multiple loops and handles. Moreover, a support generation scheme has been developed in our framework to enable the fabrication of all models. Manufacturing constrains such as the number of rotational axes can be incorporated during the orientation sampling process. As a result, our algorithm supports both the 4DOF and the 5DOF systems. A variety of models have been tested on our approach as examples. Hareware setups have been developed to take the physical experiments for verifying the effectiveness of our system.”

Co-authors of the paper are Chenming Wu, Chengkai Dai, Guoxin Fang, Yong-Jin Liu, and Charlie C.L. Wang.

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A Closer Look at 3D Printing Support Structures

Support structures are a necessary evil of 3D printing. They can be frustrating and time-consuming, but they are required to keep many parts from collapsing or becoming distorted. In a paper entitled “Support Structures for Additive Manufacturing: A Review,” a group of researchers take a close look at supports and their various forms and functions, and evaluate some of the research that has been conducted on them already.

The purposes of support structures, according to the researchers, can be divided into three types:

Supports that act as a heat diffuser and rigidity enhancer, preventing shape distortion and residual stresses due to excess heat accumulation, particularly in metal 3D printing
Supports that are necessary in processes like FDM so that material isn’t being deposited in midair
Supports that act as a tether to keep parts from shifting and/or collapsing

Support structures, while necessary, also have plenty of disadvantages, including creating excess material that often cannot be reused, as well as creating lots of extra work to remove. They also result in longer print time and additional work and expertise required to generate them properly. The paper discusses how to circumvent some of these obstacles, including optimizing the orientation of the part and the structure of the supports, as well as using sacrificial or soluble supports or support baths.

In the study, the researchers take a look at other publications that have been dedicated to 3D printing support structures, and find that the majority of them are focused on FDM 3D printing, rather than metal 3D printing processes.

“The reason for this is most probably because of the unavoidable and higher requirement of support in FDM, and the popularity of the printing technique,” the researchers state. “FDM needs material beneath the printed layer as it is extrusion-based, while for powder processes, the powder could take the role of support. In addition, the unused powder which acts as the support can be reused, to an extent, in the future. However, the supports fabricated in extrusion-based processes are generally unable to be reused, unless the supports are re-manufactured into filaments. For powder bed processes, the support material is generally for ameliorating against thermal stresses during manufacture and to anchor the printed part within the build volume.”

Many of the studies reported focus on the optimization of part orientation in order to minimize support usage, but others are dedicated to eliminating support usage altogether. One research team tried to use an inclined deposition method for FDM, but the method is a bit complex and involves control over the direction of the nozzle. Another proposal involved using water or ice as supports for SLA builds.

“Though this strategy seems to eliminate using the part material as support, it instead requires the repeated heating and cooling of water to induce the necessary phase change, which may be less energy efficient,” the researchers point out.

The design of support structures should be based on several principles. The support should be able to prevent the part from collapsing or warping, especially the outer contour area; for metal processes, stress and strain need to be considered and thermal simulation modeling can be considered for design. The connection between the supports and the final part should be the minimal strength needed, in order for removal to be as easy as possible, and the contact area between the support and final part should be as small as possible to minimize damage. Material consumption and build time should also be considered.

Support structures are unavoidable in many 3D printing processes, the researchers conclude, but more effort should be made to minimize the negative effects of supports. In the research that they evaluated, there were a few gaps that they pointed out, including the lack of a comprehensive method for reducing support material while keeping the mechanical strength and surface finish quality.

“In addition, some innovative and creative methods which can largely minimize or even achieve zero-support for AM are urgently necessary,” the researchers conclude. “Support structure modeling needs to be adopted in the future, especially for metal processes. Further, a standardized model and uniform criteria need to be made in the future for fairly comparing different support methods and choosing the most economical strategy. Lastly, topology optimization is necessary to be integrated into support structures for further reducing materials used, making AM a more sustainable technology.”

Authors of the paper include Jingchao Jiang, Xun Xu, and Jonathan Stringer.

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