DESIGN | SUSTAINABILITY
the need for greater automation by Christian Decker, CEO of Desma Shoe Machinery. Injection moulding, for example, involves 90% automated operations, in comparison with the more manual compression mould- ing process, where 25% is automated. Using an automated 3D bonding method in upper assem- bly leads to a better environmental footprint,
Above: Desma’s new NovaCoat-D, which it developed with BASF, is a combination of release agent and in-mould coating for midsole production
he said, due to savings in energy use, labour use and material use. In-mould coating and labelling methods bring similar benefits in comparison with established footwear decoration methods. They also deliver great colour and effects to the shoe design. Decker showed examples of in-mould coating producing metallic coloured midsoles. As well as adding colour, in-mould processes can be used for other purposes, for example closing TPU foam surfaces. Desma has also looked at adding a “lotus” effect through an in-mould transfer process, which prevents dust adhesion. In March, Desma announced that in collabora- tion with BASF it had developed NovaCoat-D, a combination of release agent and in-mould coating. “The highly elastic coating ensures fast cycle times on round table processes and is ideal for use with Desma machines. It has excellent mechanical properties and comes in a wide range of colours and effects,” it says.
Right: Peak Sport has incorporated 3D printed soles in volleyball shoes and other sports footwear
Additive manufacturing – or 3D printing – is another subject of interest for designers at shoe brands because of its potential to help towards sustainability improvements, as well as its potential for design freedom. At the Polymers in Footwear event, Daniel Dempsey, Engineering Manager, Manufacturing Innovation, at New Balance Athlet- ics, said a wide variety of available additive manu- facturing processes leads to complexity when companies are choosing which technology and material is suitable for any given shoe part. Brands are having to consider inferior material performance too. Dempsey said there is an approximately 20% property drop in 3D printing materials in compari- son with materials used in compression and injection moulding – this is especially the case when comparing SLS material properties with injection moulding. Key improvement targets are increased resilience, tear strength and better elongation property in elastomer materials, which are difficult to simulate in the 3D printing environment, he said.
16 INJECTION WORLD | March 2021
Peak Sport has been at the forefront of the shoe
industry’s adoption of 3D printing. In 2017, it released the first shoe with a 3D printed sole in China and has followed this up with other shoes for running, basketball and volleyball. Kui Cai, Design Director at Peak Sport’s US design centre, spoke at the footwear event about The Next, a project it started in 2019 with polyurethane producer Wanhua Chemical. The project is about rethinking the manufacture and lifecycle of a shoe and it has involved designing a fully 3D printed shoe. At K2019, Wanhua showed a prototype of the shoe made using its TPU 3D printing materials in the upper, sole and heel structure, and its binding feature. With just three main parts and a mono- material construction, the Peak Sport shoe was also designed to be completely recyclable. Materials companies made presentations at the
Polymers in Footwear virtual summit that encom- passed sustainability, polymers and processes. Kathrin Salwiczek, Senior Manager Sports & Foams at Evonik, the other major producer of PEBA along with Arkema, said PEBA foam provides higher performance than TPU and EVA foams. The company has developed flexible foam grades of its Vestamid PEBA brand which are lightweight, have adjustable stiffness and provide high energy return. PEBA foams can be used for injection moulded soles and this eliminates the issue of scrap material generated when using other processes. DSM has another alternative to foamed EVA and
TPU: its Arnitel family of thermoplastic polyester elastomers. Jacy Leong, Market Development Manager at DSM, said Arnitel is “a benchmark spring material” and, in comparison with TPU, has less dynamic creep and hysteresis (less energy dissipation). He said there is increasing interest in physical foaming for shoe design and manufacture (also see the On Cyclon shoe above). Chemical foaming is the dominant method used in footwear, but the microcellular foams created by physical
www.injectionworld.com
IMAGE: PEAK SPORT
IMAGE: DESMA
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