3D Cocooner Stable lightweight construction method in three-dimensional space 04: Light-curing plastic: using four UV lights, glass fibres and resin are merged to form a solid lattice network The art of construction and architecture is associated first and foremost with mankind. Yet impressive constructions also emerge in wildlife. African weaver birds, for example, weave artistic nests out of leaves and stalks, where hundreds of animals live over several generations. And while bees, wasps and termites construct their homes layer by layer, spiders and butterfly caterpillars create impressive shapes with the help of spinning threads. To do so, they produce a fluid that polymerises into a solid thread outside the body and can thus be shaped into sturdy webs or cocoons. Inspired by this, Festo has developed the 3D Cocooner as part of its Bionic Learning Network. Just like a caterpillar, it spins delicate shapes and creates custom-made lightweight structures out of a glass-fibre thread. With the help of a handling system, the spinneret can be precisely manoeuvred and the glass fibres, which are simultaneously laminated with UV-curing resin, are glued together to form complex structures. In contrast with other 3D printing methods, however, these structures are not built up on a surface one layer at a time, but are actually constructed freely in space. A vertically arranged type EXPT-45 tripod acts as a specialised handling system for the 3D Cocooner. The three-armed parallel kinematics system can be controlled quickly and precisely in the space and its manoeuvrability makes it ideal for such a task. Furthermore, instead of a gripper, the tripod is equipped with a specially developed spinneret, into which a 2400-tex glass-fibre roving is continuously threaded. Real-time construction with light-curing plastic In order to convert the soft thread into a solid lattice structure, it is moved forward over a pair of rollers in the spinneret and simultaneously covered with a viscous resin. As soon as it comes out, a UV light cures the fibre soaked with resin with pinpoint accuracy and hardens it into a sturdy little rod. The thread is cut off with a small cutting disc and the spinneret can start again in a different place. By exactly regulating the amount of UV light, the resin can also be temporarily kept in a liquid state in order to glue a new section together with structures already in place. In this way, it is possible to construct complex shapes in three-dimensional space without any supports. The tripod receives the necessary positional data and control signals directly from an animation software program that is normally used to create virtual 3D models, computer graphics and simulations. Digital set of rules for individual configuration The three-dimensional shape model of the desired structure is developed in the software and turned into a physical form by the spinneret. With this process, the body is not built up by traditional 3D modelling, but generated instead according to parametric construction principles. For this purpose, a set of geometric rules is stored in a specially developed program, providing the basic shape of the structure and the design parameters – such as height, width and rotation of the body as well as the shape and number of the individual meshes. The user only has to specify the parameters, while the program calculates the details automatically. With the software’s graphical user interface, even a layperson can adjust the design attributes however they want using a slide control and thus configure their individual structure from the basic shape stored in the program. Direct control of the tripod kinematics Alongside the parametrically designable object, the entire handling system is also stored virtually in the software. This allows the complete path planning to be directly calculated here and visually simulated, whereby all the key process parameters such as speeds, thread feed or amount of resin are already taken into account and exactly coordinated with each other. The actual production process is not only depicted virtually, however. It can also be started up without any further steps. At the press of a button, the program transmits the required geometry to the kinematic travel paths. The shape parameters are translated to the handling system’s control system via direct software access. This direct path from the design to the production tool is very unusual in the current production environment. It is, however, an important prerequisite for customised manufacturing processes in the future. The efficient and flexible production of batch size 1 plays an important role in the ideas relating to Industry 4.0. 01: Precise travel paths: the extremely manoeuvrable tripod kinematics allow the spinneret to move freely in space 02: Virtual depiction: both the shape model and handling system are visually stored in the animation software 03: Natural role model: the thumb-sized cocoon of this small butterfly can be found in the Ecuadorian rainforest 01 02 04 03 2 Festo AG & Co. KG 3 3D Cocooner: bionic lattice structures from the robotic spinneret
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