Many major companies, including Nike, Adidas, Reebok, Carbon and others, believe that the footwear industry could be the first major adopter of 3D printing technologies for mass production of consumer products. This is true in particular for mass customization applications. Until now, all of these companies have focused primarily on 3D printing the outsole and midsole. Voxel8, a startup with a fascinating history originating from Harvard University, is ready to bet on the rest of the shoe, the “upper” or top section, by introducing its unique ActiveMix® process for extrusion and coloring of advanced polyurethane materials.

On our recent trip to Boston, we had the great pleasure to meet one of the most important researchers in the global extrusion 3D printing and bioprinting industry: Professor Jennifer Lewis, from the Harvard Wyss Institute’s Lewis Lab. Professor Lewis is not just an expert in bioinks. She has been working on material extrusion for more than two decades. Some of her research is at the heart of Voxel8’s new technology. We had an amazing chat at Harvard. While helping us clarify many aspects of 3D printing and bioprinting’s evolution in recent years, Professor Lewis also offered some insights on her upcoming breakthrough work on bioprinting heart and kidney tissues.

Getting back down to Earth, Professor Lewis also suggested we connect with Voxel8’s co-founders Travis Busbee and Jack Minardi, to learn more about their application and its potential impact in the not-too-distant future. Even on short notice, Jack was able and kind enough to meet us and show us around the facility. It was quite an experience and, although the technology we saw is focused mainly on prototyping and short runs, the Voxel8 vision was made quite clear and could truly have an impact on shoe mass production in the not-to-far future.

Getting ready to run

After building up experience on multi-material extrusion for its pioneering electronics 3D printing system, Voxel8 is now focusing on engineering-grade polyurethanes. These viscous materials – which are sometimes considered one of the “Eldorados of 3D printing” due to the challenges and the potential rewards of being able to print them – are printed using the company’s current ActiveMix® system, in a machine that the company is calling the ActiveLab®.

In this approach, the extrusion head uses a complex pump system to enable programmable control of composition, geometry, and mechanical properties of printed features on uppers (& other textiles) as well as other 3D shapes such as midsoles & outsoles.

The result is that Voxel8 is able to 3D print polyurethane patterns on any surface. Through the integration of inkjet technology, the company can also add unique full-color images and patterns in between the polyurethane layers, enabling increased customization.

The ActiveLab® system – which is now available on the market – is tailored for prototyping and short runs, with coloring, carried out on a separate machine. Even so, the process adds several degrees of automation to an otherwise highly labor-intensive traditional approach. In addition, the upcoming ActivePro® production system will be able to integrate and further automate both processes.

“Our vision is to tackle one of the most labor-intensive areas of shoe production, which is the upper section,” Minardi explains. “several companies have been focusing on midsoles and outsoles, which are traditionally injection molded. The upper is traditionally made of a variety of materials, including different types of textiles and plastics with varying properties. Our technology enables mass customization of the uppers through a highly automated process which will bring digital design and manufacturing closer to the customer.”

Untying the laces of traditional manufacturing

There are two companies in the world that were able to bring to market an electronics 3D printer. One is Nano Dimension and the other is Voxel8. Both companies abandoned their first – somewhat “consumer-oriented”  – design in order to create a more industrial system with more practical short-term applications. Nano Dimension’s Pro system remains focused on electronics, while Voxel8 ventured into the new area of digital footwear manufacturing systems.

For both companies, the currently available systems are intended as an intermediate step toward large-scale production-oriented devices. Voxel8’s digital manufacturing systems are intended to dramatically shorten the design and production cycles for both custom-release and – in the future – large-scale production runs.

Leveraging a multimillion-dollar backing from Braemar Energy Ventures and ARCH Venture Partners, Voxel8 now has 15 engineers and 39 patents around its process. “We are approaching shoe manufacturing at the prototyping and creative level,” Minardi says. “Currently it takes 12 to 18 months for a designer to have the first version of a new product on the shelves. One of the reasons is that, while for most companies the design stage takes place in the United States, manufacturing takes place in Asia. The traditional manufacturing process requires expensive tools and mold-cutting. It is very labor-intensive, with as many as a 100 pairs of hands touching each shoe. What we are doing is automating as much of that as possible, starting with the upper section. This allows us to bring the time requirements down from 12-18 months to 2-4 weeks for a full design-to-final-product turnaround.”

Fully digital Voxel8 shoes

The Voxel8 digital manufacturing system requires zero tooling, which results in decreased set-up costs and dramatically accelerates the time to market. “We can do logos, text and other aesthetic features along with functional features like reinforcements or heel counters with zero tooling,” says Minardi. “Along with replicating traditional manufacturing processes at lower costs, we can also produce uppers that are not currently manufacturable.

For example, we can regionally vary stiffness and viscosity as we deposit the material. By digitally regulating the composition and mechanical properties of our polyurethane materials, we enable them to provide exactly the support that you need, right where you need it. In addition to that, we bring the inkjet head in to do full color in between transparent polyurethane layers. This enables us to utilize the strength, abrasion resistance and durability of industrial grade polyurethane elastomers, with the high-resolution full-color capability of inkjet technology.”

In this first phase, Voxel8 is coming to market with the ActiveLab® system, which integrates the printhead, software and proprietary material formulations. The current system is cost-effective on customized runs of 30 to 50 pairs a day, which is something that shoe manufacturers are actually starting to offer. The ActivePro® system, on the other hand, would be able to produce as many as 500,000 pairs per year at costs that are competitive or better than traditional Asian manufacturing processes.

Running up the scale

The textile materials come in a variety of forms, including rolls, flat knits, and engineered meshes. The production system will be modular to accommodate all of these. It will have an array of print-heads which deposit the first polyurethane layer with zonally tuned material properties, then an inkjet head will apply the color before another array of extrusion heads print the second layer. The next stage is an integrated curing oven, which will cure the materials in a matter of minutes, before moving on to the final stage, a laser cutter, to cut out the upper’s shape. All the operator needs to do is load the roll of textile material and the polyurethane components. In a few minutes out comes a complete, customized upper. In addition to remaining cost competitive in mass production, the ActivePro® system will enable mass customized manufacturing at scale, allowing batch sizes as small as 1.

“The best part is that you cannot tell it’s 3D printed,” says Minardi. In fact, the polyurethane comes out perfectly smooth, with no layer lines. “We can work with virtually any upper fabric, Minardi continues. “Today knit uppers are very popular, but our system enables us to apply the polyurethane to just about any type of fabric and apparel.”

At least one major footwear brand has already put in an order for the ActiveLab® system so the ball is rolling. The large format ActivePro® system is more similar – in its external appearance – to large format digital 2D printers than a 3D printer. This approach, which implements material extrusion technology while focusing on the final product, rather than on the process itself, could be the key to Voxel8’s success in finally closing the gap between 3D printing and the end-users.