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New Balance and Formlabs Launch TripleCell 3D Printing Platform and Rebound Resin for Athletic Shoes

The New Balance 990

While I’m not much for recreational jogging these days, I’ll always remember my first real running shoes – a pair of dark gray Sauconys, which I got to pick out from the store when I made the track team in seventh grade; a short-lived activity, as I was neither fast enough for sprinting nor strong enough for shot put. Shoes have changed dramatically since then in their looks and features. Manufacturing processes have only recently begun to change with new weaving techniques, more use of polymers, and 3D printing. With the way things are going these days, it may not be long before everyone’s favorite pair of athletic shoes is of the 3D printed variety, no matter which manufacturer they come from.

Back in 2015, Boston-based athletic leader New Balance announced that it was teaming up with 3D Systems to create the first 3D printed running shoe. The company released its Zante Generate shoe a year later, and while it wasn’t the first 3D printed shoe ever created, it was the first to be made commercially available.

Now, New Balance has launched a brand new premium 3D printing platform, called TripleCell, which is powered by SLA technology from Formlabs and a completely new material.

“3D printing is changing how companies approach manufacturing, with this announcement New Balance is pioneering localized manufacturing. By eliminating the dependence on molds and direct printing for both prototyping and production, their team shifts from months to hours in the development and production cycles,” said Dávid Lakatos, Chief Product Officer of Formlabs. “We’re moving towards a world where design cycles are closing in on the whim of the consumer and it’s exciting to be on the frontlines of this with New Balance.”

It all started last year, when the two Massachusetts companies announced an exclusive relationship focused on creating high performance hardware and materials, in addition to a manufacturing process for athletic footwear. They wanted to create a 3D printing production system, with unlimited design freedom, that would open up opportunities for innovation in the athletic footwear sector – a high inventory, high volume business that involves plenty of craftsmanship and manual labor. But as more people clamor for customized products, it’s getting harder to produce them without embracing modern technology.

Katherine Petrecca, New Balance General Manager of Footwear, Innovation Design Studio, said in a Formlabs blog post, “We saw innovation with 3D printers and materials and started to envision the future of how this could come together in consumer products.

“When you’re able to use techniques like 3D printing to turn to more of an on-demand manufacturing model, that’s a game changer. There are advantages both for the consumer and for New Balance as a manufacturer. On the consumer side, the ability to design and what you can fabricate with printing is well beyond what we can do with molding. It really opens up a lot of opportunity for us to make better parts than we’re making now with foam and plastic.”

Formlabs worked closely with New Balance to develop a production system to bring TripleCell to life

New Balance realized it would need a specific material that didn’t yet exist in the industry. The new TripleCell platform can deliver components that are pretty close to traditional performance cushioning, thanks to the proprietary photopolymer Rebound Resin that was developed as a result of the partnership. Rebound Resin was designed in order to make resilient, springy lattice structures with, according to a Formlabs press release, “the durability, reliability, and longevity expected from an injection molded thermoplastic.”

“TripleCell will deliver the industry’s pinnacle expression of data to design with seamless transitions between variable properties underfoot. This new, cutting edge, digitally manufactured technology is now scaling exclusively within New Balance factories in the U.S. further establishing us as a leader in 3D printing and domestic manufacturing,” said Petrecca. “Formlabs has been an integral partner to bring this to life. We’re really going to be able to disrupt the industry not only in performance, but also in athlete customization and speed to market.”

Rebound Resin has a higher tear strength, energy return, and elongation than any other Formlabs SLA material. Most foam components in current footwear are made with compression or injection molding, which limits design possibilities. But using 3D printing for prototyping and production has allowed New Balance to open brand new opportunities in the fabrication of its footwear.

“What we could do to date is engineer the outside of the shoe and rely on the inherent properties of the material to provide all the performance benefits we’re looking for,” explained New Balance Senior Additive Manufacturing Engineer Dan Dempsey. “Any degree of what you could consider customization is disparate pieces of foam glued or molded together, with a lot of assembly steps on the back end. Using additive manufacturing, we can essentially vary the lattice structure to really change localized properties inside of a single form, giving us the ability to engineer throughout the entire volume of the shoe; we can design a system from the inside out.”

Using the new TripleCell platform for both prototyping and manufacturing allows the creation of shoes with a high cushion zone, which transitions to an area of high stability, within a single design, using a single material. It also helps decrease the time to market.

New Balance Animation

“The traditional timeline for our product cycle from paper initiation to delivery in market is 15-18 months. And when we’re building tools and waiting for foam or rubber parts, we’re looking at 4-6 week lead times. By eliminating molds, we can save months of development time,” said Petrecca. “TripleCell technology makes it possible to easily produce multiple designs at the same time, reinventing the traditional iterative testing approach. We had the ability to generate and edit thousands of options before landing on the high-performance, running focused structures you see today.”

This week, New Balance launched the first product from its new platform – the limited edition $185 990 Sport, which is now shipping and features TripleCell technology in the heel for a cushioning experience on par with its classic silhouette, but is 10% more lightweight than the 990v5 shoe.

The $175 FuelCell Echo shoe will come in September, and the first full-length high performance running product will launch in 2020.

Petrecca said, “The TripleCell 3D printed components deliver more lively, spring-like cushioning than you’ve ever experienced in foam, with the ability to ultimately be produced on-demand in our own facilities in Massachusetts.”

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[Source/Images: Formlabs]

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LLNL: Magnetically Responsive Metamaterials Instantly Stiffen 3D Printed Structures

Lawrence Livermore National Laboratory (LLNL) frequently does impressive work with 3D printing materials, including metamaterials. Now the lab has introduced a new class of metamaterial that can almost instantly respond and stiffen 3D printed structures when exposed to a magnetic field. LLNL calls the materials “field-responsive mechanical metamaterials” or FRMMs. They involve a viscous, magnetically responsive fluid that is injected into the hollow struts and beams of 3D printed lattices. Unlike other 4D printed materials, the FRMMs’ overall structure does not change. The fluid’s ferromagnetic particles located in the core of the beams form chains in response to the magnetic field, stiffening the fluid and the lattice structure. This happens in less than a second.

The research is documented in a paper entitled “Field responsive mechanical metamaterials.“

“In this paper we really wanted to focus on the new concept of metamaterials with tunable properties, and even though it’s a little more of a manual fabrication process, it still highlights what can be done, and that’s what I think is really exciting,” said lead author Julie Jackson Mancini, an LLNL engineer who has worked on the project since 2014. “It’s been shown that through structure, metamaterials can create mechanical properties that sometimes don’t exist in nature or can be highly designed, but once you build the structure you’re stuck with those properties. A next evolution of these metamaterials is something that can adapt its mechanical properties in response to an external stimulus. Those exist, but they respond by changing shape or color and the time it takes to get a response can be on the order of minutes or hours. With our FRMM’s, the overall form doesn’t change and the response is very quick, which sets it apart from these other materials.”

The researchers injected a magnetorheological fluid into hollow lattice structures built on LLNL’s Large Area Projection Microstereolithography (LAPµSL) platform, which is capable of 3D printing objects with microscale features over wide areas using light and a photosensitive polymer resin. According to Mancini, the LAPµSL machine played a big role in the development of the new metamaterials, as the complex tubular structures needed to be manufactured with thin walls and be capable of keeping the fluid contained while withstanding the pressure generated during the infill process and the response to a magnetic field.

The stiffening of the fluid and, in turn, the 3D printed structures, is reversible and tunable by varying the strength of the applied magnetic field.

“What’s really important is it’s not just an on and off response, by adjusting the magnetic field strength applied we can get a wide range of mechanical properties,” Mancini said. “The idea of on-the-fly, remote tunability opens the door to a lot of applications.”

Those applications include impact absorption, such as automotive seats that have fluid-responsive metamaterials integrated inside of them along with sensors that can detect a crash. The seats would stiffen upon impact, possibly reducing whiplash. Other applications include helmets, neck braces, housing for optical components or soft robotics.

To predict how lattice structures would respond to an applied magnetic field, former LLNL researcher Mark Messner, who now works for Argonne National Laboratory, developed a model from single strut tests. Starting with a model he developed to predict the mechanical properties of non-tunable static lattice-structured materials, he added a representation of how magenetically responsive fluid affects a single lattice member under a magnetic field and incorporated the model of a single strut into designs for unit cells and lattices. He then calibrated the model to experiments Mancini performed on fluid-filled tubes similar to the struts in the lattices. The researchers used the model to optimize the topology of the lattice, finding the structures that would result in large changes in mechanical properties as the magnetic field was varied.

“We looked at elastic stiffness, but the model (or similar models) can be used to optimize different lattice structures for different sorts of goals,” Messner said. “The design space of possible lattice structures is huge, so the model and the optimization process helped us choose likely structures with favorable properties before (Mancini) printed, filled and tested the actual specimens, which is a lengthy process.”

Mancini began the work at the University of California, Davis under her adviser, materials and engineering professor Ken Loh, who is now at the University of California, San Diego. According to Loh, the concept was partially inspired by automotive-based suspension systems. They began by investigating ways to develop flexible armor that could morph or change its mechanical properties as needed.

“One of the criteria is to achieve fast response, and magnetic fields and MR materials offer that capability,” said Loh.

He also said that the researchers will explore new ways to develop a single-phase material, instead of having a liquid embedded in a solid, and higher performance-to-weight rations. Future work, he continued, “could lead to new technologies, such as flexible armor for the warfighter that stiffen instantaneously when a threat is detected.”

Authors of the paper include Julie A. Jackson, Mark C. Messner, Nikola A. Dudukovic, William L. Smith, Logan Bekker, Bryan Moran, Alexandra M. Golobic, Andrew J. Pascall, Eric B. Duoss, Kenneth J. Loh and Christopher M. Spadaccini.

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Investigating Lightweight 3D Printed Structures for Sand Casting

3D printing is often used to produce molds for casting. In the case of sand molds, binder jetting is typically used; however, its high costs, due to expensive materials, need to be lowered, according to the authors of a study entitled “Mechanical Analysis of Ceramic/Polymer Composite with Mesh-Type Lightweight Design Using Binder-Jet 3D Printing.” In the study, the researchers investigate the mechanical properties of sand molds with a lightweight structure for low material consumption and short process time.

Binder jetting is a faster method of making sand molds than conventional casting, but it’s still too expensive, according to the researchers. In the study, they work to find a methodology of the lightweight design in a smaller length scale for binder jetting 3D printing, such as a typical conformal lattice cell in metal.

“To investigate the mechanical properties of lightweight designs, we introduce a basic unit block sample of a ceramic/binder composite applied to a whole sand mold using a BJ 3D printer in this study,” they explain. “The selection of two different structures was just done in this research for the purpose of comparing a typical lightweight design for metal with our ideal structure. We also address geometrical effects, such as the size and shape of typical lightweight patterns provided by commercial DfAM software on the basis of mechanical property evolution.”

To study the basic design factors of a lightweight structure for a sand/polymer composite, the researchers introduced two types of lightweight structures: a box with square holes (Type-1) and a lattice with upper and bottom pads (Type-2). The specimens were 3D printed using a sand binder jetting 3D printer from voxeljet.  A compression test was performed by placing the samples between circular steel plates. Each test was conducted twice for accuracy. Each sample was broken by initiation of cracks, and no creep was observed.

The researchers also conducted computational analysis in order to predict stress distribution and fracture under uniaxial-loading, and FEM simulations were carried out. Several major conclusions were reached from the study:

The strength of both designs significantly decreased with increasing volume ratio. The size of the inner hold in the Type-1 sample should be at least 2mm for taking out the inner sand powder cleanly. Although the Type-1 sample had higher strength, it was more difficult to take out sand particles from the samples than it was with Type-2. Therefore, future studies will focus on enhancing the low strength of the Type-2 sample.

With mesh-type lightweight structures, increasing pad thickness and decreasing mesh area results in increasing local stress concentration at the interface of the mesh and pads. Easy cracking is initiated at a comparatively weak boundary between mesh and pads in the case of thick pad thickness.

“Since a commercial software for topology optimization provides lightweight designs for rigid single component materials such metals or plastics, it is not suitable to apply the lightweight designs to a ceramic/polymer composite with different mechanical behaviors,” the researchers continue. “As a result, new types of light weight structures for sand casting molds are required to spread BJ 3D printing technology to the foundry industry.”

Finally, further work will suggest and evaluate the new lightweight and rigid design for additive manufacturing of a ceramic/polymer composite. It should reveal the correlation between structural and mechanical factors of the lightweight designs in detail.

Authors of the paper include Dong-Hyun Kim, Jinwoo Lee, Jinju Bae, Sungbum Park, Jihwan Choi, Jeong Hun Lee and Eoksoo Kim.

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3D Bioprinting: Comparing Lattice Scaffolds with Traditional Rectangular Sheets

Bioprinting is not a simple endeavor – if it were, we would likely be transplanting 3D printed organs by now. It’s a delicate process that requires a number of factors to be in place, including bioinks that are both printable and biocompatible, and proper scaffolds. In a paper entitled “A Comparative Study of a 3D Bioprinted Gelatin-Based Lattice and Rectangular-Sheet Structures,” a group of researchers compares scaffolds with lattice mesh geometries to more traditional flat rectangular sheets.

“We hypothesised that the experiments performed as a part of this study would help us to observe considerable differences between the two structures, i.e., lattice and rectangle, and also open up the possibility of significantly enhancing the design of a 3D bioprinted construct for engineering cardiac tissue-on-a-chip, using bioprinting,” the researchers state.

The researchers used furfuryl gelatin (f-gelatin) as a base for their bioink, which they seeded with mouse mesenchymal stem cells. They used an ALLEVI 2 bioprinter to print the ink into two different structures – a lattice and a rectangular sheet. Rheological characterization of the bioink was conducted, and the bioprinted structures were cultured in an incubator. A live/dead cytotoxicity assay was performed, and the texture of the lattice was analyzed by scanning electron microscopy.

“The SEM cross-sectional image of the gelatin lattice revealed a highly organized, striated, patterned, and networked structure in comparison to the loosely networked and largely porous rectangular-sheet cross-section SEM, as reported in our previous study,” the researchers explain. “Porosity and pore-size are crucial to ensure cell colonization of the scaffold, deposited using bioprinting. Likewise, SEM micrographs showed a homogeneous distribution of equal sized pores within the entire area scanned and imaged….The average apparent porosity of this lattice structure was estimated to be about 50% compared to 21% for the rectangular-sheet. The results led us to conclude that although the mean pore size was significantly reduced by printing in the form of a lattice, the inherent design of the lattice allowed pores to be of a similar size and to be homogenously distributed throughout the entire structure, compared with the rectangular-sheet.”

Swelling behavior of the gels was monitored to study the hydration dynamics of the crosslinked hydrogel structure. Cell proliferation was assessed and flow cytometry was analyzed.

Results of the testing showed that the lattice structure was more porous than the flat rectangular sheet. It also exhibited a lower degradation rate.

“Further, the lattice allowed cells to proliferate to a greater extent compared to the rectangular-sheet, which initially retained a lower number of cells,” the researchers state. “All of these results collectively affirmed that the lattice poses as a superior scaffold design for tissue engineering applications.”

A scaffold is literally a foundation to build upon in bioprinting, and having an effective scaffold is key in any bioprinting application. Cells rely on a strong scaffold in order to survive and proliferate. A printable, biocompatible ink is also crucial for cells to be able to grow into tissue. The researchers find in this study that lattice structures are superior to rectangular sheets, which could mean the difference between success and failure in future applications.

Authors of the paper include Shweta Anil Kumar, Nishat Tasnim, Erick Dominguez, Shane Allen, Laura J. Suggs, Yoshihiro Ito, and Binata Joddar.

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Study Examines Compressive Behavior of 3D Printed Lattice Structures

Lattice structures are frequently found in additive manufacturing, as their complex forms are easy to make using 3D printing. The technology also makes it possible to construct them from multiple materials. Because of their high specific strength and stiffness, lattice structures are often used in the aerospace, defense and automotive industries. In a paper entitled “Compressive Behavior of Strut Reinforced Kagome Structures Fabricated by Fused Deposition Modeling,” a group of researchers investigates the compressive performance of modified Kagome unit cells.

Kagome is a type of lattice structure defined by the researchers as “a stretch dominated 3D truss structure derived from the design pattern of a woven basket.” A modified version of Kagome structure is strut reinforced Kagome (SRK), which has been shown to have better compressive properties than standard Kagome. For the study, the researchers used ABS to 3D print SRK structures.

“Uniaxial compression tests were carried out in Shimadzu Universal Testing Machine using 10 kN load-cell, and compression load was applied under displacement control at a rate of 0.1 mm/min,” the researchers explain. “Video extensometer TRViewX was used to measure the accurate displacement between the faceplates. The engineering stress-strain data are obtained from the measured force (F) and displacement (h). The stress was calculated by dividing the force by the effective area which is obtained in terms of truss length ( l = 2c) 2 3 c2, whereas the strain is obtained by dividing the displacement by the core height.”

The tests showed that the peak strength and effective modulus increase with the decrease in the slenderness ratio. In addition, SRK structures show different failure behavior with the change in the slenderness ratio.

“The core with lowest relative density (d =2.4 mm, h = 35mm) shows the failure within the linear elastic regime,” the researchers continue. “As the slenderness ratio is very high, the struts failed by elastic buckling without any yielding. With the increase in the relative density (d =2.4 mm, h = 25 mm), there is some plastic deformation before reaching the peak strength as shown in the Figure 2. With further increase in relative density (d = 3 mm, h = 25 mm), we can see the significant plastic nonlinearity before reaching the peak strength. The stress gradually decreases with the increase in the strain.”

The vertical struts in all the samples started to deform after substantial compression. Plastic bending of the vertical strut results in the distortion of the upper and lower part of the SRK, leading to the deformation of the slanted struts. Further compression leads to the formation of surface cracks on the tensile side of the strut. With further loading, the cracks open, leading to the bending of the structure, additional cracks on all sides, and eventual softening and collapse of the structure.

“The anisotropic material behavior and the porous nature of FDM printed structure have led to the discrepancies in the numerical and experimental results,” the researchers conclude. “The performance of SRK unit structure can be further improved by the variation in diameter of the slanted and vertical struts to optimize it for a given density.”

Authors of the paper include Rinoj Gautam, Sridhar Idapalapati, and Estella Siew Lee Koh.

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Researchers Test 3D Printed Lattice Structures as Implants to Facilitate Bone Growth

The advances being made in bioprinting and tissue engineering mean that even the most severe injuries have a chance at being repaired. Loss of bone due to injury or disease used to be a permanent condition, but that’s not the case anymore – medical technologies including 3D printing are now capable of replacing or even restoring lost bone tissue. New tissue can actually be grown from scaffolds that are implanted inside the body, as long as those scaffolds are made from osteoconductive material, which is a material that is capable of stimulating the growth of bone tissue.

A group of researchers recently conducted a study in which they used selective laser melting (SLM) 3D printing to generate titanium lattice structures as scaffolds for bone regeneration. The research is published in a paper entitled “Osteoconductive Lattice Microarchitecture for Optimized Bone Regeneration,” which you can access here.

“Bone replacement materials need to be accepted by the body and should clinically be infiltrated with bone tissue within a short time, so ideally they are osteoconductive,” the researchers explain. “Bone tissue engineering of osteoconductive biomaterials like other tissue engineering approaches normally relies on the combination of cells, bioactive factors, and biomaterial scaffold to facilitate and accelerate the regeneration of bone tissue.”

The shape of the bone scaffold can be designed to perfectly match the size and shape of the bone defect. In the study, the researchers 3D printed titanium structures to replace bone in rabbits, using SOLIDWORKS software to design the implants.

“The outer macrogeometry of the implants is designed as stepped cylinders of 7.5 mm, respectively, 6 mm diameter and a height of 4.2 mm,” the researchers state. “The inner microarchitecture is constructed by cutting out symmetrically arranged square channels in all three orthogonal directions, see Figure 1. Based on most promising scaffold parameters from the literature, the width of the channels w (distance between the rods) and the wall thickness s (rod caliber) of the remaining trusses have been systematically varied in a way that complete layers of cubic unit cells are formed along the cylindrical main axis (see Fig. 1 for an overview of the designs and Table 1 for the structural values). Finally, a 0.2 mm fine ring completes the outermost margin of the framework to close the last layer and prevent sharp edges during surgery.”

The implants were 3D printed using a Realizer 250HT from SLM Solutions. 18 adult rabbits were used in the study; they were housed in groups of two to four and each had four scaffolds applied to them at random. After four weeks, the implants were removed and studied to see how well they had stimulated bone growth, with distinctions being made between implants with different rod distance and rod caliber in a lattice titanium microarchitecture. The results showed that the best results were achieved at a rod distance of 0.8 mm and a rod caliber of 0.3 to 0.4 mm.

“Since AM and 3DP in many cases yield in a lattice microarchitecture, these results suggest to overcome the former dogma on channels of 0.3 to 0.5 mm and substitute them by channels of 0.8 mm for bone substitutes, where bone ingrowth has to occur fast and efficiently,” the researchers conclude.

Authors of the paper include Michael De Wild, Chafik Ghayor, Simon Zimmerman, Jasmine Rüegg, Flora Nicholls, Felix Schuler, Tse-Hsiang Chen, and Franz Z. Weber.

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