3D Printing Revolutionizes Custom Design Of Polyurethane High-End Running Shoes

All major sports apparel brands are researching the possibility of printing high performance footwear and are backed by manufacturers of materials and printing equipment.

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Adidas has established a strategic partnership with Carbon, a 3D printing specialist in the United States, to jointly manufacture Futurecraft 4D high-performance shoes. The German sportswear brand stated that it uses 17 years of operating data to design a new midsole and uses a digital footwear component manufacturing process that eliminates the need for traditional prototyping or molding.

The Digital Light Synthesis (DLS) process used by Carbon uses digital light projection, oxygen-permeable optics, and liquid resins to make high-performance, durable polymer products.

Performance parameters

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The operating data of the Adidas library was used to incorporate functional considerations in the midsole design. The use of these data allows Adidas to design a midsole that combines athletic, cushioning, stability and comfort.

Compared to standard 3D printing manufacturing methods, the DLS process is said to solve problems such as low production speed and scale, poor surface quality, and color and material limitations.

The midsole is made of liquid, Adidas said, forming a grid with 20,000 individual support points to optimize energy return.

Nike now also begins to print uppers. Eluid Kipchoke won a victory in the 2018 Vikings London Marathon wearing a pair of 3D printed TPU shoe uppers. The company claims this is the first time that high-performance shoe uppers have been made in this way.

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The way to victory

The upper is made using solid deposition modeling. In this method, filaments are unwound from the coil, melted, and then layered. Nike says that printing technology can make prototypes 16 times faster than other production processes.

The company also uses this technology to incorporate athlete-specific data into textile geometry. Nike uses data obtained from athletes and analyzes these data to confirm the ideal composition of the material. This analysis will be used to design textiles.

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The company claims that 3D printed textiles are more dynamic than traditional woven fabrics. This is because the warp and weft threads are intertwined.

The company stated that "The advantages of Flyprint textiles are reflected in the blending characteristics of materials. In knitted or woven textiles, there is frictional resistance between interwoven covered yarns and weft yarns. In printed textiles, it is more likely to realize precise coordinated control. ."

It also added that 3D printed textiles are "lighter and more breathable" than earlier fabrics.

Rapid development

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The Zoom Vaporfly Elite Flyprint on Kipchoge's feet was designed based on his feedback on the shoes he wore at the 2017 Berlin Marathon. The shoes he wore in the London Marathon in 2018 were 11 grams lighter than the first time.

The Reebok liquid factory process was launched in 2016 and uses software and robotics to draw shoes in three dimensions. The liquid polyurethane material that BASF makes for Reebok is used to accurately draw the parts of the shoe in a three-dimensional plane.

The fluid velocity shoe made using this polyurethane system can be directly made outsole instead of a sole made out of a mold alone. Once absorbed, the material will begin to solidify. The wings of the outsole are surrounded by "wings" to provide more customized fit and better support for the entire foot.

Improve performance

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New Balance and Formlabs, a 3D printing specialist in Boston, signed an agreement in 2017 to implement larger-scale 3D printing. The two companies are developing footwear-specific materials and printers for manufacturing products that improve athlete performance. Its photo-curing print Form 2 powers the printing process.

This is not the first time New Balance has been involved in 3D printing: As early as 2013, Jack Bolas became the first track and field athlete to compete with spiked shoes made using custom 3D printing technology. To complete the design, New Balance uses force plates, in-shoe sensors, and motion capture systems to simulate events to obtain individual biomechanical data.

This initial 3D printing project led to the subsequent further study of custom printing of soft parts required for the midsole. New Balance launched Zante Generate in 2016 and called it the first full-length 3D printed midsole. It uses 3D system DuraForm TPU elastomer laser sintering powder for selective laser sintering manufacturing process to make midsole layer by layer. The resulting product is a midsole with a complex honeycomb structure. New Balance claims that it has achieved an "optimal balance" in terms of flexibility, strength, weight, and durability.

Bonded together

3D printed soles and uppers must still be glued together after they are made. According to Atom Lab, the most challenging step encountered in the technical field of the Atom R&D unit is to bond the outsole to the upper. The company has teamed up with Covestro to develop a process that uses digital printing to apply adhesive polyurethane raw materials to shoe soles or shoe uppers.

Atom uses a variant of the fuse making hot melt layer technique to apply the adhesive. Melt the filaments of the melt processable adhesive first, then apply the melt adhesive according to the digital print layout, and then apply pressure to connect the sole to the upper, creating a strong and permanent adhesive bond between the two. .

According to Atom, this application of adhesive filaments is fast and efficient. Accurate and repeatable, suitable for absorbent bases. Solid filaments are used so no additional drying process is required.

In addition, the adhesive is applied from the melt and is preactivated. If the settling time is long enough, there is no need for pre-heat activation, which saves two processing steps.

Although it is still at an early stage and development is focused on high-end limited edition products, these projects clearly show that the development potential of polyurethane materials may make large-scale implementation of additive manufacturing a reality in the sportswear market.

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