APPLICATION OF ADDITIVE TECHNOLOGY IN FOOTWEAR DESIGN

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1 APPLICATION OF ADDITIVE TECHNOLOGY IN FOOTWEAR DESIGN Suzana KUTNJAK-MRAVLINČIĆ, Sandra BISCHOF and Ana SUTLOVIĆ University of Zagreb Faculty of Textile Technology Prilaz baruna Filipovica 28a Zagreb Abstract: Footwear functional parts of complex shape can be made with high precision and good dimensional tolerance using 3D printing method. It also has the possibility of making very thin layers and a smooth surface of the products which makes it very valuable in the development of new technology and products. Creation of a 3D prototype is providing the 2D procedures a possibility of developing an individual segment of footwear, fifht, soles, heels, accessories or the whole model with complex geometry. Additive technology enables usage and mixture of different materials providing diversity of shapes, mechanical features and colours. It also provides wider opportunities for the designer offering easier production of functional and wanted spatial and planar shape. Further investigation of the potential of the additive technology as advanced technology in footwear design will be focus on testing the aesthetic and functional aspect within project ADVANCETEX. Keywords: additive technologies, 3D printing, footwear design, model development 1. Additive technology Additive technology (AT) is new and emerging technology promising great revolutions in production processes. Unlike conventional machining which uses subtracting method in additive technology product is made by addition method. This technology is changing the concept of standard production process, from the design to the product itself [1]. At the beginning AT was used for the fast making of prototypes (Rapid prototyping RP), tools and moulds or their key components (Rapid Tooling - RT). But with the development of the materials that are being used in additive process, small batch or individual production occurs (rapid Manufacturing RM) [2]. Development of 3D prototypes and models with the help of 2D procedures offers a wide range of possible applications. 3D printing technology is just one of many developed additive technologies which stands out with its relatively low price and its wide application [1]. Significant advantage of this procedure is the possibility of coloured models production that can be easily replaced, according to the new designers ideas. 3D printing is often used as synonym for additive technology, despite the fact that original name indicate additive technology working on the principle of inkjet nozzles. The term "3D print" is ingrained in the public and involves the production technology that works on the principle of adding material layer by layer. The technology was patented by MIT (Massachusetts Institute of Technology) in ASTM (American Society for Testing and Materials) International Committee F42, which represents the field of additive manufacturing technology, together with technical committee ISO 261 made a decision on the categorization of AT in additive manufacturing and jointly define standard in January 2012 [2]. Additive technologies are being used for almost 30 years by now and during that period several technologies were allocated with this group. The most frequently used today are: stereolithography (SL/SLA), PolyJet, selective laser sintering (SLS), 3D printing (3DP), fused deposition modeling (FDM), laminated object manufacturing (LOM), digital light processing (DPL), laser engineering net shape (LENS) and direct metal deposition (DMD), electron beam melting (EBM), selective laser melting (SLM) [3]. Additive technology is rather simple. It is based on few technologies and uses following phases: CAD modeling, transformation of CAD model into STL or AMF file, shifting STL file to AM machine and virtual cutting of the file into layers, adjusting the parameters of the AM machine, making the creation and extracting the creation [4]. 1

2 1.1 Application area 3D printing, especially coloured printing, has given the engineers and designers a clear insight in design process, offering, the possibility of highlighting various parameters, easy and early spotting of possible mistakes and their quick and effective correction[3]. Furthermore, production time is shorter and prototype quality is increased. Up to now, 3D printing has been used in various fields: industrial design, building, architecture, automobile, air, military, dental and medical industry, bio-modeling, geo-info systems, molecular chemistry, fashion, footwear, jewelery, education and many more [4]. 1.2 Additive Processes Categorization and definition of additive process according to ISO/ASTM 52921: 2013 E) includes the following groups: 1. Extrusion materials- process of additive production in which the material in the liquid state selectively passes through the nozzle (figure 1). This process is based on FDM technology. Polymer threads (possibility of printing with multy-heads) are being melted within the extruder head. The viscous material is supplied to the nozzle where the narrowing of the nozzle reduces the volume of material, which results in precise details. The melt is solidified at room temperature. Abbreviations used for the process labeling: FDM (Fused Deposition Modeling), FFF (Fused Filament Fabrication) [5]. Figure 1 Fused Deposition Modeling (FDM) [6] 2. Dispersion of the material- process of additive production that includes material in the form of droplets that is being selectively deposited by spray (figure 2). This faze also includes hybrid stereolithography (SLA/SL) and 3D printing (3DP). This procedure was developed by the company Objet Geometries. Usually 2 heads that contain jets are being used (up to 1536 pieces). Liquid photopolymer (and support wax/gel) is applied on the surface of the previous layer by spray and with the help of a UV lamp, polymerization is carried out. Names/abbreviations that are used for labeling the procedures: PolyJet, ProJet, MultiJet Printing (MJP) [3]. Figure 2 Stereolithography (SLA) [6] 3. Binders dispersion- process of additive technology where the material in powder form selectively binds spray liquid adhesive (figure 3 and 4). This process was developed and patented by MIT entitled 3D printing. Procedure is based on inkjet nozzles, with which the liquid binder is applied on powder material. Materials that are being applied are metal matrix composites, composite materials (polymer with additives) and sand with additives. Abbreviations used for labelling technology: 3DP (3D printing) [2]. 2

3 Figure 3 3D printing (3DP) [7] Figure 4 The material jetting system as used by Objet [6] 4. Lamination- process of additive technology where the model is being built by laying and bonding (welding) the material in the shape of film, foil, sheets and panels (figure 5). This process is a hybrid of adding and separating the material so as to build a model by adding layers according to the z axis, which are then being cut in the shape of cross-section according to the contours of the model in the X-Y plane. The material can be shaped like a paper, polymeric film or a foil, made of metal / ceramic plates or composites with epoxy matrix and amplified glass. It was patented by the company Helsys. Abbreviations used for labelling the procedures: LOM (Laminated Object Manufacturing), SDL (Selective Deposition Lamination), UAM (Ultrasonic Additive Manufacturing) [3]. Figure 5 Principle of Laminated Object Manufacturing (LOM) using rolls of product material (left) and a cutting laser [6] 5. Photopolymerization - process of additive technology in which the polymerization of liquid, photosensitive, polymer material is performed selectively or simultaneously with the help of UV light source. Stereolithography is the first procedure used in rapid production of prototypes. Liquid photopolymer (acrylic, vinyl or epoxy resin) is used for building a model and a UV laser beam for solidification (selectively), DLP (Digital Light Processing) or LED UV projection (simultaneously). Abbreviations used for labelling technology: SL, SLA (Stereolithography), DLP (Digital Light Processing) [3]. 6. Merging powder (in the chamber) - process of additive technology in which, with the help of thermal energy, the powder is being selectively coalesced or melted in a heated chamber (figure 6). Laser beam or beam of electrons is directed to previous, warmed up, powder material in the chamber which is coalesce under high temperature (SLS, DMLS) or it is melted completely (SLM, EBM, DMLM). Polymers, metals and ceramics are being used for building this model. Abbreviations and titles that are used for labeling this procedure: SLS (Selective laser sintering), SLM (Selective laser melting), DMLS (Direct metal laser sintering), DMLM (Direct metal laser melting), EBM (Electron beam melting) LaserCusing, BluePrinter [3]. Figure 6 Selective Laser Sintering (SLS) using a 3 bin system [6] 7. Direct deposition of materials process of additive technology where the material is directly being melted and deposited using heat energy. Laser beam or beam of electrons is directed onto a very narrow area which melts the powder delivered by the nozzle or wire material. Various metals are used for making this model. Abbreviations and titles that are used for labelling this method: LENS (Laser Engineering Net Shaping), DMD (Direct Metal Deposition), Electron Beam Free Form Fabrication [2]. 3

4 2. Additive technology in footwear design Using additive technologies oriented on development of new footwear models enable the production of three-dimensional prototypes and small series of produced CAD models. 3D printing, as one of the few additive technologies that are commonly used today, can create functional parts of very complex footwear shapes with high manufacturing precision, good dimensional tolerance, very smooth surface of the parts and a possibility of making very thin layers which can have a very important role in the field of new technologies and products. One of big advantages of this procedure is a possibility of making coloured models which can additionally be altered. Application of 3D printing technologies in the production of footwear model-prototype includes various tests that help to determine esthetic aspect of the product. Additionally it offers easier connection of the design elements with the anthropometric characteristics and the geometry of the feet. Creating elements of footwear; bottom of the shoes (figure 7), soles (figure 8), heels and many functional and decorative elements or a complete model with simple or complex geometry (figure 9). a) b) c) d) Figure 7 Examples of the shoes bottom: a) PROSPECS W by TROCKS, b) Suela vestir by Juan Galvan, ind. Suajes, c) Woman's sandal by Elton Anold, Padova Moldes, d) 3 "Myth" 3D printed shoe collection [8] a) b) c) Figure 8 Examples of heels: a, b) 3D Printed heel hybrid shoe by Karrie Luft, c) Shoe from Anastasia Radevich [9] a) b) c) Figure 9 Examples of printed models of women s shoes with simple and complex geometries: a) Oxford Shoe by Angel, Digital Evolution System Co., b) Organic by Nico barrera, ico design, c) 3D Printed sole hybrid shoe by Victoria Spruce [8] Industrial design typically consists of three-dimensional and surface characteristics; such as ornaments, patterns, lines or colours or their combination. Application of additive technologies allows footwear designers to create various of creative shapes. In addition to design characteristics in the development of models of shoes, if the final goal is actual usage, it is necessary to satisfy both functional and ergonomic criteria. To accomplish of advanced technologies are usually combined with traditional techniques of shoe making (figure 10). 4

5 a) b) c) Figure 10 3D printing shoe by Katrien Herdewyn: a) sketch of the model, b) 3D printed part, c) finished model with additionally added colour and supplemented by elements from the natural skin [10] Three-dimensional printing technologies can also be applied in installing components of footwear. Most common is the making of sole either for mass consumption, orthopedic uses or for individual/ personalized needs (for example: production of sports shoes) (figure 11). a) b) Figure 11 Examples of sole: a) SOLS, A Maker Of 3D-Printed Shoe Insoles, b) 3D Print a Custom Insole [11] 2.1 Work stages The development phases in all of the procedures of additive manufacturing are: CAD modeling (figure 12), converting to STL or AMF file, transfer of the file to the AM machine, adjustment of the parameters of the AM machine, the production of formation and post processing and application [4]. Features of the used materials which notably affect the final appearance and technical characteristics of the product differ significantly depending on the type of AM. PolyJet procedure gives possibility to use and mix different materials which allow a variety of forms, mechanical properties and colour. The materials used in the PolyJet procedure are usually photopolymer acrylic materials. This procedure provides more possibilities for the designer in the creation of the desired functional spatial and planar shapes, but the high price of the device is a disadvantage. Today, 3D printers are mostly used, due to the relatively low cost of the device. MakerBot Industries is one of the leading companies which designs and manufactures 3D printers (figure 13). ABS (acrylonitrile butadiene styrene) and Polylactic acid (PLA) are common plastics used in 3D printing. Bot of them are particularly strong plastics and available in a wide spectre of colours [5]. Figure 12 Rhionoceros Figure 13 MakerBot 3D printer Apart of limitations in choice of materials and limitations in size because of the relatively small working surface, 3DP has many advantages: possibility of making thin layers, very smooth surface, good dimensional tolerances of creations, high speed operation of the machine, possibility of using machines in offices, low price and it doesn t require high energy to function and the materials can be reused. 3D printable models can be created with a computer aided design (CAD) package, via a 3D scanner or via a plain digital camera and photogrammetric software [5]. 2.2 Areas of application in the industrial and fashion design 3D printing has spread into the world of clothing with fashion designers experimenting with 3D-printed bikinis, shoes, and dresses. In commercial production Nike is using 3D printing to prototype and manufacture the 2012 Vapor Laser Talon football shoe for players of American football (figure 14), and New Balance is 3D manufacturing custom-fit shoes for athletes. 3D printing has come to the point where companies are 5

6 printing consumer grade eyewear with on demand custom fit and styling (although they cannot print the lenses). On demand customization of glasses is possible with rapid prototyping [1]. Figure 14 Nike Vapor HyperAgility Cleat built for the Shuttle drill features 3D printed cleat plate [12] 3. Conclusion The contemporary footwear design and the current fashion trends are imposing increasingly higher and faster requirements on the development process of the sample model. The offer of the market is oriented in favour of the small batch, and often of the individual (personalized) production and for the making of patterns or finished consumer products the advanced additive manufacturing procedures are more and more used. The application of additive technologies oriented on the development of model products of footwear allows the production of three-dimensional prototypes and small series of manufactured CAD models. The creation of three-dimensional shape of the prototype and footwear model using the 2D-tier procedure offers opportunities for the development of the individual segments of footwear; outsoles, soles, heels and functional and decorative elements or the whole complex geometry model. One of the drawbacks in the 3D printing process is a small number of applicable materials, which therefore limits the footwear design process. Using the PolyJet procedure it is possible to use and mix different materials which enable the variety of forms, mechanical properties and colour. This procedure provides wider possibilities for the designer in the creation of the desired functional spatial and planar shapes, but the disadvantage is the high price of the device. Main goals of the research conducted as part of the ADVANCETEX project is to test the applicability of 3D printing for different stages of footwear modeling, so as the possibility of applying 3D printing in the footwear industry. 3DP will give clear insight into the course of the design and enable rapid changing of various parameters, so as the early and easy detection of possible errors following with their quick and effective correction. References [1] Berman, B.: The new industrial revolution; Business Horizons (2012) 55, [2] Godec, D., Šercer, M., Aditivne tehnologije 4. Industrijska revolucija, Tehničke znanosti, glasnik akademije tehničkih znanosti hrvatske, Vol. 19(1) 2015, ISSN [3] Šercer, M.; Godec, D. & Pilipović, A.: Aditivne tehnologije za mala i srednja poduzeća; literatura tiskana za deseminaciju projekta [4] Krznar. N., Šercer. M., Pilipović. A., Razvoj i izrada polimernog proizvoda pomoću taložnog očvršćivanja, Tehničke znanosti, glasnik akademije tehničkih znanosti hrvatske, Vol. 19(1) 2015, ISSN [5] Godec. D., Vidović. I., Šercer. M., Optimiranje parametra niskobudžetnog 3D tiskanja, Tehničke znanosti, glasnik akademije tehničkih znanosti hrvatske, Vol. 19(1) 2015, ISSN [6] engineering/rm/rm%20processes/ Accessed: [7] Accessed: [8] Accessed: [9] Accessed: [10] Accessed: [11] Accessed: [12] Accessed: Acknowledgements The work has been supported by Croatian Science Foundation under the project 9967 Advanced textile materials by targeted surface modification, ADVANCETEX. 6