3D printing shoes is a continuing hot topic because it is closely related to our lives.

In the early years, 3D printing was mainly used for footwear prototype manufacturing and proof of concept. That is, in the early stage of product design, the designer puts forward the design concept and uses 3D printing to transform it into a physical model for further design and improvement.

With the advancement of technology and the improvement of people's needs, direct manufacturing is considered to be the development trend of 3D printing in the field of shoemaking. As the name implies, direct manufacturing refers to the direct use of 3D printing to produce the final product. With the development of 3D printing technology and material technology, as well as the improvement of people's individual needs, the use of 3D printing for direct manufacturing of footwear will become more and more common.

Personalization: Why use 3D printing to make shoes?

Since Nike first adopted 3D printing technology to manufacture football shoes in 2013, major footwear manufacturers have embraced 3D printing technology, including Adidas, New Balance, Under Amour, and domestic brands like Peak and Li Ning. For the shoe industry, the reason why 3D printing technology is so important comes from the demand for personalization and customization.

Each of us has different weight, foot type, running posture, landing style, etc. Even the left and right feet of the same person will be different. Through three-dimensional scanning, foot dynamic analysis and other technologies, it is possible to produce shoes that perfectly match the shape of each person's foot.

Let's take the domestic brand Li Ning as an example to see how to achieve personalized customization of 3D printed sports shoes.

First, a three-dimensional scan of the consumer's foot is performed to obtain the basic data of the foot shape, including foot length, foot width and other related parameters.

Then, the plantar pressure testing equipment is used to collect the dynamic distribution of plantar pressure during running, and obtain data such as the pressure distribution area and pressure level at various places of the plantar.

Finally, after obtaining all the above data, take foot shape, weight, plantar pressure size and distribution as one of the parameters, using modeling technology and simulation analysis technology, the program will automatically generate the plantar three-dimensional mesh structure, and finally get A 3D printed sole structure that perfectly matches the weight, foot shape and plantar pressure distribution.
It is understood that HP has cooperated with Superfeet, a 3D printing insole company, to launch the FitStation platform, which provides personalized customization through 3D scanning and gait analysis. The actual development process of the new shoe is as follows: first analyze the user's foot, and then use Superfeet's injection molding machine to produce the general part of the shoe, and then pass variable PU injection, foot pressure measurement, runner's joint movement analysis, and personal preferences Create customized sneakers.

Belgian software company Materialise and HP reached a cooperation agreement to design and manufacture fully customized 3D printed insoles. The HP FitStation platform integrates Materialise's software to realize 3D design automation, printing preparation and production management functions.

When it comes to 3D printing insoles, Belgian Materialise is a pioneer in this field. Through Phits launched in 2014, Materialise has joined hands with RS Scan, an expert in foot dynamic analysis, to become the world's first company to produce 3D printed insoles based on the dynamic measurement of plantar pressure.

Using 3D printing technology, people's customization needs have been met. In addition to the great advantage of personalized customization, 3D printing has many benefits, including reduced production cycle, reduced inventory risk, complex structure manufacturing, lightweight manufacturing, etc. These advantages have attracted more and more companies to enter the 3D printing system. The shoes are under development.

Manufacturing technology and materials

If you divide a pair of running shoes into three parts: upper (Upper), midsole (Midsole), outsole (Outsole). If you think of a shoe as a car, the upper is equivalent to the body, the midsole is equivalent to the suspension system, and the outsole is the tire. It can be seen that the midsole is the soul of running shoes, and it is also the core symbol that distinguishes major manufacturers, and the foundation of standing.

The midsole of shoes is extremely important to human comfort. The role of the midsole is to provide stability, cushioning and rebound, absorb the impact generated during exercise, and provide protection and a relatively mild foot feel during exercise.

At present, most 3D printed shoes use 3D printing technology to manufacture shoe midsoles.

▌Laser sintering technology

One of the more common technologies for manufacturing shoe soles is laser sintering technology (SLS), which uses high-intensity lasers to sinter TPU powder and form it layer by layer. Laser sintering 3D printing is one of the widely used 3D printing technologies. Nowadays, parts printed by SLS technology can be found in airplanes, automobiles, production tools, and wearable devices.

Using SLS technology to manufacture sports shoes, representative manufacturers include Nike, New Balance, Under Armour and Chinese brands Peak and Li Ning.

Peak 3D printed shoe FUTURE3.0, the sole and upper are made of 3D printing technology, which makes the product present the characteristics of high strength and light weight.

Under Armour "Futuristic" soles made using SLS technology

▌Light curing technology

Adidas and 3D printing company Carbon have reached a partnership to jointly produce the new 3D printed sports shoes Futurecraft 4D. The manufacturing technology is Digital Light Synthesis (DLS), which uses resin materials and has a better surface finish than laser sintering technology SLS.

"Light curing molding" (SLA) is a type of 3D printing technology, but it has always been limited by the durability and plasticity of photosensitive materials. So stereolithography is suitable for making prototypes, but not for producing final parts. In addition, the speed of stereolithography is relatively slow, and it takes hours or even days to complete the manufacture of large parts.

Carbon has the core 3D printing technology of Continuous Liquid Interface Production (CLIP), which realizes continuous and uninterrupted printing, which is 25-100 times faster than traditional light-curing 3D printing. The 3D printing technology is unique to Carbon. The increase in 3D printing speed is Carbon's killer feature, and it also makes mass production of 3D printed sports shoes possible.

Printing process

According to "Market Watch" (Market Watch) reports, by 2023 at the latest, 20% of the products of Nike and Adidas will be personalized.

FDM technology (fused deposition modeling) is the most popular 3D printing technology. This technology does not involve dangerous links such as laser, high pressure, high temperature, etc., and the cost is lower than other 3D printing technologies.

The American start-up company Prevolve uses FDM 3D printers to manufacture whole shoes, using flexible TPU wires. The printing time for each shoe is 20-30 hours

Nike applied FDM 3D printing technology to shoe uppers and made an innovative attempt. The material used is flexible TPU wire. Compared with the previous woven shoe uppers, the shoe upper has a higher density, which not only does not generate unnecessary friction, but also improves the tensile strength and torsion resistance of the upper.

FDM technology has now begun to move towards the consumer side. It is understood that the ECCO STUDIO Store opened by ECCO in Shanghai has begun to try 3D printing personalized customized shoes to the consumer side. The printing material is silica gel with good resilience and flexibility. The sole printing time is about 2 hours, and no post-processing is required after printing.

▌Return manufacturing to Germany?

Facing the problem of rising labor costs in Asia and slow supply chain speed, Adidas deployed a "fast factory" to transfer production back to Germany, and tried to apply 3D printing and other automated production methods to the entire process of sports goods production to reshape this value 80 billion dollar industry.

Once, when Adidas' "Fast Factory" factory appeared in front of the public, "Adidas moved back to Germany!" The voice made some overseas factories worried. In the "fast factory", it can be done within 1 week from design to delivery. The company claims that once the design is completed, this production cycle may even be compressed to one day. Adidas said that they will not hire a lot of labor like factories in Asia, each factory only needs 160 people.

Made in China (Made in China) is one of the most recognized labels in the world. China is the world's largest manufacturing country, has the world's most complete industrial system, and is the world's "manufacturing country". If the customization of 3D printing can be realized on a large scale, whether China can still maintain the reputation and actual status of the "country of manufacturing" is an issue that needs attention.

As we all know, the mainstream manufacturing process in the world today is mold technology, which is known as the "mother of industry". However, just when everyone thought that molds were irreplaceable in the industry, a new manufacturing process came out, and that was 3D printing.

Before the advent of 3D printing, personalized custom shoes were difficult to achieve because the cost was too high. Nowadays, based on the comprehensive use of various technologies such as 3D printing, robotics, and artificial intelligence, mass production in the field of shoemaking is entirely possible to be replaced by personalized custom designs. Judging from the current development momentum of Adidas fast factories, the labor-intensive traditional shoe-making model may face greater pressure.