AMS Spring 2023

Covestro TPU Used to Make 3D Printed Insoles

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3D printed orthotics are not new to our industry, but this particular project is. Using Create it REAL‘s software suite and Covestro Addigy FPU 79A thermoplastic polyurethane (TPU), as well as GenbioX’s Cubic software, and orthopedic service provider GeBioM mbH‘s expertise in the field, these partners have created a solution for producing shoe insoles with fused deposition modeling (FDM).

“Our new TPU plastic and a printer developed specifically for this application make it possible to print very soft structures. The material and printer were harmonized during development to achieve a perfect result. With the help of the automated software solution, soft and hard structures can be combined in a shoe insole, achieving a level of customization that was previously virtually impossible,” said Business Development Manager Lukas Breuers at Covestro.

The company also says that, “The TPU also meets the requirements for medical devices with regard to cytotoxicity and skin sensitization in accordance with the DIN EN ISO 10993-5 and 10993-10 standards.” Ultimately they want to make recycled TPU insoles as part of their circular economy drive.

“It was important to us that the new solution also allows for improved sustainability. Currently, the production of insoles also generates large amounts of waste. Moreover, the insoles themselves are hazardous waste after use. With 3D printing, we now enable our customers to produce in a waste-free manner by using only the material that is needed for the insoles,” Marcel Domenghino, Managing Director of GeBioM, stated.

I love how they’ve cobbled together an alliance and optimized a printer specifically for this. By taking the Cubix CAD software to determine the hardness and softness of parts and to change the gradient, tying in the Create it Real software for automatic file handling, and marrying it to a material and printer, they’ve got a nice alliance that can be used to deploy this solution.

Ever since Steve Wood aka Gyrobot made variable-density insoles with FDM in 2014, I’ve thought that material extrusion would be the most fruitful technology in making insoles. Yes, surface finish sucks, but the costs are lower, we can use more materials, and we can make variable density insoles. So, we can change the infill pattern in 2D, change the pattern in 3D, change the infill across the sole, change wall thickness of infill walls and change infill density and height at every voxel. In turn, we can make a sole that is not only customized to your foot but is customized to your walk, tread and the settlement of the foot at every point . This same level of performance will be hard to do or impossible with CNC, powder bed fusion, and vat polymerization. You could do it to a certain extent with lattices, but not with the same granularity and performance. The cost advantages are also important in the shoe market as well.

So, if you solve the surface texture issue which technologies such as DyeMansion’s VaporFuse or AMT’s PostPro3D, which have been developed specifically to finish soft 3D printed parts, there may yet be solutions to this problem. If they can also bring the costs down of post-processing significantly, as well as increase surface finish, this may be a mass-market opportunity for us. FDM systems have had a difficult time 3D printing TPU traditionally and we do not yet know how optimized the feed system in this project is compared to what we’re used to. Assuming that they can run this at higher speeds than usual, we can either see an in shop printing solution or a centralized service.

Many companies and entrepreneurs have focused on the shoemaker-in-a-box solution that involves 3D printing at the retail location. Typically, this difficult to do, but would address issues we have of joining disparate 3D printed and traditionally made parts by relying on manual labor. Centralized 3D printing by services may also make sense if they can invest in serious automation to offset labor costs and reduce the price to more palatable levels.

TPU is a very soft material that has a lot of wear and abrasion resistance and is already used widely in many industries including footwear. The material is also weldable which could point to potential solutions to join together different parts. Polypropylene would also be an option, as well would PCL.

Can FDM match the productivity and reliability needed to make shoes at scale? Will the cost be doable for footwear companies? Of these elements, we can not entirely be sure. Shoe firms have been moving away from leather to shoes that are almost entirely polymer. At the same time, they have been ditching retailers and doing their own sales online.

The shoe market is undergoing major changes at the moment. 3D printing may yet have a role to play. At the time of these changes shoe companies could change their technology or offer special, custom-fit shoes in limited numbers. But, even if they don’t adopt 3D printing, the much higher-margin orthopedics business could be our only real client. However, this protected enclave of businesses would bring relief and comfort to many people through higher value mass customized solutions. So, perhaps, this would be better for us long term?

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